ATTACHMENT C TapRooT® Investigation Report Subsurface Contamination Incident … · 2020-04-01 ·...

ATTACHMENT C

TapRooT® Investigation Report

Subsurface Contamination Incident Port Hope UF6 Plant

July 13, 2007

October 15, 2007

Attachment C: TapRooT ® Report of 63 Subsurface Contamination Incident October 15, 2007

Glossary of Terms

AECB Atomic Energy Control Board A & E Audits and Evaluations BH50-2, etc. Borehole series wells CARs Corrective Action Recommendations CNSC Canadian Nuclear Safety Commission CTCW Cell Tempered Cooling Water Eldorado Eldorado Nuclear Ltd. ERA Environmental Risk Assessment ‘Floors, Sumps & Trenches’ Floors, Sumps, Trenches, Pits and any associated Joints Golder Golder Associates Ltd. KOH Potassium Hydroxide MOC Management of Change MOE Ontario Ministry of the Environment NI Needs Improvement NDE Non Destructive Examination N-S Trench North-South Trench PHA Process Hazard Analysis Pit Effluent Pit PM Preventive Maintenance RW Refinery Well SPAC Standard, Policy or Administrative Control Specs Specifications Study Area Effluent Treatment, Cell Room, and Cell Maintenance

Area UF6 Uranium Hexafluoride UO2 Uranium Dioxide


Table of Contents

1.0 EXECUTIVE SUMMARY .................................................................................. 4

2.0 OVERVIEW OF THE INVESTIGATION PROCESS..................................... 8

2.1 INVESTIGATION SCOPE......................................................................................... 8 2.2 ROOT CAUSE ANALYSIS PROCESS........................................................................ 8 2.3 INFORMATION COLLECTION (I.E. “WHAT HAPPENED”)........................................ 8 2.4 CAUSAL FACTOR (PROBLEM/ISSUE) DEFINITION................................................. 8 2.5 ROOT CAUSE ANALYSIS....................................................................................... 9 2.6 CORRECTIVE ACTION RECOMMENDATIONS ......................................................... 9

3.0 EVENTS LEADING UP TO THE INCIDENT ............................................... 10

4.0 CAUSAL FACTORS AND SUPPORTING INFORMATION ...................... 18 4.1 CAUSAL FACTOR #1 – SOME ‘FLOORS, SUMPS & TRENCHES’ ARE NOT DESIGNED TO

RESIST A CORROSIVE ENVIRONMENT ...................................................................... 18 4.2 CAUSAL FACTOR #2 – LIQUID ENTERING ‘FLOORS, SUMPS & TRENCHES’ IS

FREQUENTLY CORROSIVE AND ATTACKS THE STRUCTURES .................................... 21 4.3 CAUSAL FACTOR #3 –URANIUM + CHEMICALS FREQUENTLY ENTER THE ‘FLOORS,

SUMPS & TRENCHES’.............................................................................................. 22 4.4 CAUSAL FACTOR #4 – LIQUID AND SLUDGE REMAIN IN THE ‘FLOORS, SUMPS &

TRENCHES’ FOR SUSTAINED PERIODS OF TIME........................................................ 24 4.5 CAUSAL FACTOR #5 – SOME ‘FLOORS, SUMPS & TRENCHES’ DETERIORATED OVER

TIME AND BEGAN TO LEAK ..................................................................................... 27 4.6 CAUSAL FACTOR #6 – THE MONITORING PROGRAM DOES NOT DETECT

DETERIORATION OF AND/OR LEAKAGE FROM THE ‘FLOORS, SUMPS & TRENCHES’ . 31

5.0 CORRECTIVE ACTION RECOMMENDATIONS....................................... 34

APPENDIX 1................................................................................................................... 39

APPENDIX 2................................................................................................................... 43

APPENDIX 3................................................................................................................... 60


1.0 EXECUTIVE SUMMARY

In 1980, Eldorado (Eldorado Nuclear Ltd.) made an application to the AECB (Atomic Energy Control Board) for Site Approval of Port Hope Conversion Facility UF6 (Uranium Hexafluoride) Facilities Expansion. This was followed by a Construction Application. Lummus carried out the detailed design of the new UF6 Plant, which would be called Building 50. Building 50’s trenches and the concrete floor were not considered as potential leak paths for uranium or chemicals in the Lummus design and construction documentation. Further, there were some ‘floors, sumps & trenches’ (term represents floors, sumps, trenches, associated joints and the Effluent Pit) that were not designed to resist a corrosive environment (e.g. the Cell Room trenches did not have a chemical resistant liner, as there was no specific design requirement identified). The intent of Cell Room trenches in the design documentation appeared to be to collect small amounts of tempered cooling water from leaks in the cells and hold the tempered cooling water pipes. Experienced personnel interviewed during the investigation into the subsurface contamination did not recall much focus placed on the trenches during the design and early operation. The first UF6 Plant operating activities took place on April 2, 1984, at which point the Operations Quality Assurance Manual took effect. The focus of this manual was safety related systems, a designation for equipment and systems that had the most significant environmental impacts. These systems were also identified as part of the design and construction process. ‘Floors, sumps & trenches’ were not considered part of a safety related system. The UF6 Plant experienced numerous operating problems from the onset in all process areas, including liquid effluent. According to one senior individual interviewed as part of this investigation, "There were so many challenges associated with the UF6 plant in the beginning that effluent/water related problems were of lower priority." The water volume experienced during operation was greater than design expectations. Being the low point, the Pit was primary collector for excess fluid. These water balance problems in Building 50 resulted in flooding of the Pit, causing water to back up into the unlined Cell Room trenches on several occasions. Potentially corrosive liquid frequently entered ‘floors, sumps & trenches’, including Cell Room trenches under normal process conditions. Cameco Corporation purchased the assets of Eldorado on October 5, 1988. Not only did corrosive liquids make their way into the ‘floors, sumps & trenches’, but also uranium and chemicals frequently entered the ‘floors, sumps & trenches’ through other pathways, including floor sweepers. Right from start-up in 1984, floor sweepers cleaned the process floors in Building 50 and were discharged into the N-S Cell Room trench and equipment was routinely cleaned on the floor of the effluent area. A relatively significant source of uranium to the ‘floors, sumps & trenches’ would have been the tanks, which by design, occasionally overflowed to the floor in the


Effluent Room. A channel for uranium containing liquids from this tank to get into the Pit and Cell Room trenches was provided when a shallow trench was cut into the floor in the Effluent Room. Another problem that contributed to this incident was that the liquid and sludge described above remained in the ‘floors, sumps & trenches’ for sustained periods of time. The Cell Room trenches could not be routinely cleaned because they had piping (between 4" and 8") running down their length. Golder Associates Ltd., a technical consulting firm commissioned by Cameco to examine the integrity of the concrete structures and the extent of the subsurface contamination, examined the Cell Room trenches and indicated the solution in the trenches may have pooled in places and did not flow through the trench as designed. During the coring of the south trench, Golder noted that the coring water actually flowed a short direction west (up gradient) instead of east (down gradient). As a result, uranium contaminated sludge built up in the North and South Cell Room Trenches. There are strong indications that some ‘floors, sumps & trenches’ deteriorated over time and began to leak. This resulted in uranium and chemicals seeping through the cracks and holes in the concrete into the soil and eventually migrating to the ground water below. This is a very slow process that could well have gone on for years during which the cracks/holes in the concrete trenches and floors, for the most part, went undetected. The monitoring system did not detect this deterioration and/or the leakage from the ‘floors, sumps & trenches’. In 2007, a contractor began work on a rectangular excavation in Building 50 of the UF6 Plant. The excavation was to house a new CTCW (Cell Tempered Cooling Water) tank, which is desired due to an increased number of cells. The new CTCW tank was to be placed in a concrete in-ground structure. The design specified double walled protection. As well, monitoring of the integrity of the tank was to be part of the new design and operation. On July 12, 2007, the contractor pulled a small tree root from the soil in the excavation. Water was noticed leaking into the excavation from the hole left by the tree root. The next day, the contractor noticed a yellow stain in the bottom of the excavation. The yellow stain was found on the surface of freshly poured concrete in the excavation. Cameco management were notified and began to investigate. Cameco immediately recognized that the yellow stain was associated with uranium. Cameco then voluntarily shut down UF6 production operations and initiated an investigation into the source of uranium contamination. Cameco promptly advised the CNSC (Canadian Nuclear Safety Commission) and the MOE (Ontario Ministry of the Environment) Spills Action Centre of the incident. The MOE Spills Action Centre notified Environment Canada. On July 19th, a complete plant shut-down was initiated to facilitate the expanded scope of investigation. In the


subsequent investigation, subsurface contamination was confirmed in Building 50. Consistent with all large incidents, and most small ones, there is no single cause. The investigation has identified 6 major problems (referred to as “Causal Factors”) that preceded the incident. If these problems had not existed, there is a reasonable probability that the subsurface contamination below Building 50 would either not have occurred or the consequences would have been less extensive. It is critical for the reader to understand that all 6 of these Causal Factors must have occurred for uranium to be discovered in the excavation for the new CTCW tank in the UF6 Plant on July 13, 2007, and subsurface contamination to be subsequently confirmed. A discussion and basis for the 6 Causal Factors appears in Section 4 of the report. Appendix 1 illustrates the relationship between the 6 Causal Factors. The Causal Factors are:

1. Some ‘floors, sumps & trenches’ are not designed to resist a corrosive

environment; 2. Liquid entering ‘floors, sumps & trenches’ is frequently corrosive and

attacks the ‘floors, sumps & trenches’; 3. Uranium and chemicals frequently enter the ‘floors, sumps & trenches’; 4. Liquid and sludge remain in the ‘floors, sumps & trenches’ for sustained

periods of time; 5. Some ‘floors, sumps & trenches’ deteriorated over time and began to leak;

and 6. The monitoring system does not detect deterioration of and/or leakage

from the ‘floors, sumps & trenches’. Recommended corrective actions were developed to address all of these causal factors and are summarized as follows:

a) there is a need to identify ‘floors, sumps & trenches’ as a safety related

system because of the potential for leak paths. This aspect must be reflected in the Safety Report and application of the Quality Assurance program. Appropriate design, construction and operating standard(s) and management change controls must be established and maintained. Some minimum requirements were identified;

b) there is a need to carry out a design related assessment of credible acute and chronic challenges to ‘floors, sumps & trenches’ and then ensure their structural surfaces are appropriately designed. The designs must be developed as per an approved design standard to ensure requirements (e.g. Preventive Maintenance (PMs) and maintaining as-built drawings) are clearly documented, communicated and implemented;


c) there is a need to implement an effective corrective action program so that problems are routinely identified and appropriate corrective action taken; and

d) there is a need to assess the adequacy of the groundwater monitoring program for early leak detection, and implement any necessary improvements.


2.0 OVERVIEW OF THE INVESTIGATION PROCESS 2.1 Investigation Scope

The investigation examined the relevant events and conditions leading up to the subsurface contamination incident at Port Hope on July 13, 2007. The investigation reviewed information as far back as 1980 when the UF6 Plant was designed and constructed. Both basic and root causes of the contamination incident were identified, as well as corrective action recommendations to significantly lessen the chances of this type of incident occurring in the future.

2.2 Root Cause Analysis Process

The investigation was conducted using the TapRooT® Root Cause Analysis process. This process was developed in 1988 and is internationally recognized and used by organizations from many different industries. The investigation process consisted of four main steps, namely, a determination of: 1. What happened (SnapCharT®); 2. Issues or Problems (Causal Factors); 3. Why the incident happened (Root Cause Analysis); and 4. Corrective Action Recommendations (CARs).

2.3 Information Collection (i.e. “What Happened”)

Numerous individuals (both current and retired) were interviewed as part of the information collection process. Some of those interviewed were directly involved in the design, construction and/or operations leading up to the contamination incident. Others were more indirectly involved, and were interviewed for their technical and background expertise and knowledge. Numerous reports, detailed correspondence and photographs were also reviewed and considered. An important information source for this investigation consisted of reports from Golder, a technical consulting firm commissioned by Cameco to examine the integrity of the concrete structures and the extent of the subsurface contamination. Relevant information was assembled into a detailed SnapCharT®, creating a time-ordered listing of relevant events and associated conditions. The complete SnapCharT® is detailed in Appendix 2 of this report.

2.4 Causal Factor (Problem/Issue) Definition

Six Causal Factors were identified for the subsurface contamination incident. Causal Factors are general problems or issues. The Causal Factor numbering


reflects their order in time sequence and NOT their relative priority. This time sequencing of Causal Factors may be observed in Appendices 1 and 2. There is no prioritization of Causal Factors. The premise is that if any one Causal Factor had been removed or significantly changed prior to the incident, then there would be a good chance the incident would not have occurred or its consequences would have been significantly reduced. A discussion of and basis for each Causal Factor appears in Section 4 of the report. A visual illustration of the six Causal Factors, and how they relate to each other and the subsurface contamination incident, may be seen in Appendix 1. Each Causal Factor is associated with, or more accurately the result of, numerous conditions. The conditions provide additional information and help to explain why the Causal Factor existed.

2.5 Root Cause Analysis

The TapRooT® Root Cause Analysis process calls for each Causal Factor to be analyzed for root causes using the TapRooT® Root Cause Tree. The process requires the investigator to identify as many root causes as are supported by the information collected. The root causes detail why the Causal Factor was allowed to exist. It is important to note that there is no ‘root - root cause’ to an incident (or to a Causal Factor). Typically, there are several Causal Factors associated with an incident and for each Causal Factor, there are several root causes. The Port Hope UF6 Plant contamination incident was typical in this regard. Identification of valid root causes permits the formulation of effective and practical Corrective Action Recommendations (CARs).

2.6 Corrective Action Recommendations

A total of four CARs were developed to address the root causes stemming from the six identified Causal Factors. These are detailed in a Corrective Action Matrix in Section 5 of this report.


3.0 EVENTS LEADING UP TO THE INCIDENT

In a letter of October 29, 1980, Eldorado applied to the AECB for Site Approval of the Port Hope Conversion Facility UF6 Facilities Expansion. Previously, Eldorado carried out UF6 conversion in the East Plant. In a letter of December 17, 1981, Eldorado applied to the AECB for Construction Approval for the Port Hope Conversion Facility UF6 Facilities Expansion. At the time, focus was placed on gaseous and liquid emission control and monitoring. The groundwater-monitoring program was established as part of UF6 expansion in advance of operation. The program was primarily intended to protect the underground storage tanks at the municipal water works. Lummus carried out the detailed design of the UF6 Plant. A task force, made up of Eldorado personnel, was established to oversee the project. Their prime responsibility was to provide oversight and technical input to Lummus. Lummus’ design documents and the construction manual did not consider ‘floors, sumps & trenches’ as a potential leak path for uranium or harmful chemicals. Lummus designed and constructed the concrete floors, sumps, pits and associated joints in Building 50. ‘Floors, sumps & trenches’ were not considered to be a safety related system and some structures were not designed to resist a corrosive environment. The Cell Room trenches were not coated with a chemical resistant substance as there was no specific design requirement identified to do so. Section 405, pg 22 of the design manual stated, "Floor in the 300 area is rarely (almost never) washed down. Floor will be swept unless electrolyte spilled." While the design documentation was not specific, the intent of Cell Room trenches appeared to be to collect small amounts of tempered cooling water from leaks in the cells and hold the tempered cooling water pipes. When additional cells were added in 1996, the philosophy did not change. However, the design that Spectrum Engineering provided for this project detailed specifications on the Cell Room Expansion, including detailed directions on how to install water stop. Lummus provided no equivalent detail for water stop for the original Cell Room. As background, water stop is used to provide a water tight seal between two joining concrete elements. The joints between joining concrete elements, such as floor slabs and walls create a discontinuity (cold joint) in the concrete and form a plane through which water can permeate. Water stop is used as a barrier across this discontinuity and, when installed properly, prevents water migration across the discontinuity. Going back to the initial Lummus design, all process sumps were steel lined with a space between the liner and the underlying concrete. The trenches in Cell Maintenance, the Effluent Room and the Flame Reactor area were lined with a chemical resistant coating. The floor of the effluent treatment area was coated, a


portion of which was covered with metal plating. The Pit was coated with a chemical resistant liner. The construction joints were “typically described” in Lummus Design Drawings. For example, Section 9.1 of the concrete design document stated - "Where indicated on the drawings, water stops shall be embedded in the concrete at joints.” There was no indication on the Cell Room concrete drawings that a vertical joint was present at the wall line of the trench. This may have had an impact on the joint material used and may be why a water stop was not used in the vertical joint that was later found to have failed. Experienced personnel interviewed during the investigation into the subsurface contamination did not recall the trenches being much of a focus at all during the design and early operation of the UF6 Plant. Lummus completed design documentation for Eldorado in the early 1980s and the UF6 plant was commissioned. The first UF6 Plant operating activities took place on April 2, 1984. The Operations Quality Assurance Manual, which applies to safety related systems, took effect at the same time. As indicated earlier, ‘floors, sumps & trenches’ were not considered part of a safety related system. Right from the beginning and in all parts of the process, including liquid effluent, the UF6 Plant experienced numerous operating problems. According to one senior individual interviewed as part of this investigation, "There were so many challenges associated with the UF6 plant in the beginning that effluent/water-related problems were of lower priority.” A Process Technology Group was set up in 1985. The intent of this group was to improve operational effectiveness of the UF6 Plant. Members of the group were involved during design and commissioning of the plant. Being the low point, the Pit served as the primary collector for excess liquid. The water volume experienced during operation was greater than design expectations. Operational problems resulted in the Pit flooding on several occasions. The Pit flooding resulted in water backing up into the unlined Cell Room trenches. This, at times, necessitated the use of an outside tank. Two tanks were originally located within the Pit to receive the process fluids from Cell Maintenance. However, sludge from Cell Maintenance kept plugging the tanks and it was difficult to remove the sludge from the tanks. A decision was made in December 1984 to remove the two tanks and the associated pump from the Pit. The change was implemented by the fall of 1986. As a result of the change, the functionality of the Pit, as primary collector, was extended to include what had been the influent to the tanks. A shallow trench was cut to join the Effluent Room trench to the Cell Room trench system very early in the operation of Building 50. The trench was to provide a path for liquid from excursions in the Effluent Room to reach the Pit. The trench also directed liquid flow away from Door 16. No formal design change


was carried out, as this system was not considered a safety related system. Connecting the Effluent Room trenches to the Cell Room trench system unintentionally introduced additional uranium into the Cell Room trenches and into the Pit. Moving forward in time, liquid frequently entered ‘floors, sumps & trenches’, including Cell Room trenches. A resulting problem was the liquid entering ‘floors, sumps & trenches’ was frequently corrosive and attacked the structures. During the current investigation, Golder found that some unlined concrete ‘floors, sumps & trenches’ in the study area exhibited signs of deterioration from aggressive solutions. In their report, Golder states - "In the area where the south trench from Cell Rooms meets the north-south trench, the surface of the floor slab exhibits deterioration similar to the walls of the trenches. It appears there may have been aggressive solution on this surface in the past.” There is a clearly a difference in appearance between the bottom half of the concrete and the top half of the concrete in the original Cell Room trenches. The bottom half appears as though it has been chemically attacked while the upper half appears fully intact. This is an indication of a "wicking type action" from chronic and corrosive wetness in the trenches. It is probable that dilute acid, most likely from the electrolyte solution in the cells, neutralization of the sticks used to manually check cell electrolyte level and/or the acid wash station in the Effluent Room used to clean plant equipment removed from service, pickled/attacked the concrete and any joints in the trenches. Cell cooling coils sometimes failed and the electrolyte from the cells entered the cooling water, making it mildly acidic. This, in turn, attacked the cooling water pipes. Some failures have been experienced where the cell cooling water pipes connect (e.g. on the threads) to the main header in the trench. Electrolyte spills from cells and resultant cleanup was another way liquid in trenches became corrosive. One Operator stated that all 30 Cells in the Cell Room have “puked” several times due to over-pressurization. The standard approach has been to wait for the electrolyte to dry and then scoop it into drums. The residue was then washed into trenches. Neutralization solution used to wash the sticks used to monitor cell levels was discharged into the trench. There is no written procedure for this activity. The solution could be corrosive if not done properly. Another source of corrosive liquids reaching ‘floors, sumps & trenches’ was large equipment washing on the floor near the trenches. This operation directed fluids to the trenches. Going back to the chronological time sequence, Eldorado/Cameco made process improvements in the UF6 Plant as time progressed. Several interviewees commented, “We have better control of water now than with the original design.” One person stated that it used to be batch operation through the scrubber towers and now it is more continuous.


Cameco Corporation purchased the assets of Eldorado, including the Port Hope conversion facility, effective October 5, 1988. On October 7, 1990, a leak of process fluids/effluent out of Building 50 occurred through Door 16 in the Effluent Room. A six-inch high berm in front of Door 16 in the Effluent Room was repaired in October 1990. However, it was not until 2003 that a formal PM on the berm was instituted, although an informal operations check was being performed. In combination with the problem that corrosive liquids presented to ‘floors, sumps & trenches’, uranium and chemicals also frequently entered the ‘floors, sumps & trenches.’ Most interviewees were not surprised to learn that uranium was found in the Cell Room Trenches. Right from start-up in 1984, floor sweepers have cleaned the process floors in the UF6 Plant and were emptied into the N-S Cell Room trench. It was easy for the floor cleaners to empty their machines in close proximity to the CTCW Tank because of the availability of water to flush the equipment. The risk of this practice was not recognized. This operation likely contributed to some of the uranium in the sludge in the Pit and the trenches. Sludge sample results for this investigation for uranium in Cell Room ‘floors, sumps & trenches’ are as follows: 1. North Trench - Middle Section = 2,100 ppm 2. North Trench - East End (old Cell Room) = <40 ppm 3. North Trench - West End (new Cell Room) = 1,200 ppm 4. South Trench - West End (new Cell Room) = 2,100 ppm 5. South Trench - Middle Section = 10,600 ppm 6. South Trench - East End (old Cell Room) = 5,300 ppm 7. CTCW enclosure = 56,000 ppm

A relatively significant source of uranium to the ‘floors, sumps & trenches’ would have been the tanks, which by design, occasionally overflowed to the floor in the Effluent Room. A channel for uranium containing liquids from this tank to get into the Pit and Cell Room trenches was provided when a shallow trench, for which no installation records have been located, was cut into the floor in the Effluent Room. Also, pieces of equipment that did not fit in the wash tank in the Effluent Room were hosed down on the floor, the residue flowing to the Pit. When the Pit was cleaned in 1990, the sludge was found to contain 17% uranium and 1,153 ppm arsenic. An additional contributor to this incident was that liquid and sludge remained in the ‘floors, sumps & trenches’ for sustained periods of time. The Cell Room trenches were not able to be routinely cleaned because they had piping (between 4" and 8") running down their length. The Cell Room trenches could only be cleaned on a few occasions when the CTCW piping was changed out.


At times, the Pit partly flooded to the extent that its overflow flooded the North and South Cell Room trenches. The CTCW Tank installation, which was connected to the N-S trench, was designed such that liquid and sludge became trapped in the interstitial space between the tank and the concrete. Also, the Pit maintained a sludge and liquid level for extended periods of time. Effluent Room trenches also contained sludge and liquid but these were frequently cleaned out for operational reasons. Trenches in and around the Cell Room appear to be sloped such that liquid flows into them and is unable to fully drain out. There are also localized low points, perhaps created partly by surface deterioration, in both the North and South trenches. Elevation data may be viewed in Appendix 3. The trenches in the East and West Cell rooms are roughly 50 and 36 metres in length (164 and 118 ft) respectively. The design intent was to grade/slope the trenches so that water flowed out. A Design Drawing Note states “all bottom of trenches to slope max. 1/16 in. in 12 in. u.n. (unless noted).” This would result in a maximum elevation change of 10.25 in. over 164 ft. The Design Drawing does not specify a minimum slope. Elevation measurements show the as built conditions for the Cell Room trenches have an average gradient of 1/32 inches in 12 inches. The difference between the highest and lowest measured elevations in the South trench in the East Cell Room is approximately 4.8 inches. There are localized low points in both the North and South trenches. Golder’s examination of the Cell Room trenches indicated the solution in the trenches may have pooled in places and did not flow through the trench as designed. During the Golder coring of the south trench, they noted that the coring water actually flowed a short direction west (up gradient) instead of east (down gradient). Indications are that some ‘floors, sumps & trenches’ have deteriorated over time and began to leak. This resulted in uranium and chemicals seeping through the weakened locations in the concrete. Uranium and chemicals entered the soil and slowly migrated. This was a very slow process that appears to have gone on for years. As part of the UF6 plant construction, eight Refinery Wells (RWs) were installed around Building 50 primarily to protect the municipal water supply. These RWs have not yet detected any ground water contamination from Building 50 operations. Following the discovery of subsurface contamination, Golder was contracted to carry out a comprehensive study. They made the following observations in their reports: The groundwater monitoring data from the new borehole series wells

indicate general impacts beneath the Cell Maintenance Room, in the general vicinity of the Pit and concrete trenching just upstream of the Pit;

The trench running north-south that connects the two trenches in the Cell Rooms to the Pit is exhibiting considerable deterioration in areas and some


of the cracks observed are the likely sources of uranium and chemicals leaking from the trench system into the soil;

Inspections undertaken as part of the concrete assessment indicate the potential for leakage to the subsurface to have occurred from several locations and/or features within the Study Area (Effluent Treatment, Cell Room, and Cell Maintenance Area) in addition to the immediate vicinity of the excavation for the new CTCW structure;

A 150 mm diameter core was taken vertically on the north side of the South trench at the east wall through the joint. The core revealed that the joint is approximately 15 mm wide with the top 12 to 20 mm of the joint sealed. A metal rod could be inserted along most of the vertical length of the joint deep enough to reach underlying soil;

The concrete around a drain pipe leading under the slab from the trench at the North Door (Door 16) in the Effluent Room into the filled in trenches exhibits considerable deterioration;

The CTCW concrete retaining structure that contained the cooling water tank exhibits some surface deterioration but no cracking or delaminations; and

The grout layer on the bottom of the Pit was delaminated but the underlying concrete was sound. After further investigation, a leak path from the Pit was not located.

The PM program in place to check the condition of ’floors, sumps & trenches’ in the UF6 Plant was limited to the berms, checking of the sumps in the Effluent Room and the AHF unloading area trench. While there is evidence that repairs have been done to the “floors & sumps”, it appears these were carried out as needed and not as part of an overall PM program. One Golder concrete specialist stated that expansion joints typically have a service life. There is no documented requirement for joint maintenance in any design documentation and there is no indication that the expansion joint, found leaking in the South Cell Room trench, had ever been inspected. Deterioration in the concrete trenches and floors, for the most part, went undetected. The only formal monitoring system (i.e. RW system) has not yet detected leakage from the ‘floors, sumps & trenches.’ Some repairs to the ’floors, sumps & trenches’ were carried out on an individual basis. Cell Room Operators indicated they did not notice the condition of the trenches as they were behind the Cells, there was a steel grate on top of the trenches and Operators did not go back there very often. No requirement was specified for inspection in the design or safety manual because it was not recognized as a potential leak path. As a consequence, there was no program in place to inspect trenches.


As part of the PHA (Process Hazard Analysis) process, the area engineer was asked to develop a NDE (Non Destructive Examination) test to determine whether the sumps in the Effluent Room were leaking. He developed such a test and checked the Effluent Room sumps on an ad hoc basis. An NDE test was not developed to check for leaks in other “floors, sumps & trenches” beyond the Effluent Room. An area engineer began checking sumps for leaks in the Effluent Room in 1993-94. By 2000, a leak test determined that sumps 405FA11 and 405FA01 needed to be removed from service. Upon sump liner removal, the leakage was determined to be by way of the carbon steel liner. No breach of the concrete chamber had occurred. The 1990 Annual Report indicated that the Pit was cleaned during the summer shutdown. The liquid level in the Pit was visually monitored over the 3-month shutdown and appeared to remain stable. The report indicates that any leak in the containment, if it exists, is small. The June 1990 ERA (Environmental Risk Assessment) listed current preventative measures for the leakage scenario from the Pit as follows: "Pit was probably not intended to continuously hold liquid. The bottom and part of the side walls were acid-proofed in case tanks in the Pit failed. However, at present, there is no evidence of significant leakage. Liquid level likely above the acid proofed section of side walls but is caustic, not acidic. Pit level monitored, no sign of steady level loss at present." An assessment for ground water monitoring was carried out during the 1990’s. At the CNSC’s request, this work was re-assessed in the late 1990’s and finalized in early 2000. The work was done by Golder. The June 2006 Safety Report (Issue 4) contained the following statement: "Sumps continue to be checked for leakage at least once per year by the area engineer." In April 2006, a CTCW tank inspection indicated it would need to be replaced within a few years. Cameco decided to advance the schedule and replace the CTCW tank in 2007. Safety Report (Issue 4) in June 2006 indicated that only some sumps (401FA14 (UF6 plant), 35G18 and 51G106 (UO2 plant)) specify double lined, maintained dry and solids regularly removed. In the Environmental Aspects Registry, contamination of groundwater was only considered from sumps in the tote bin area. There was no reference to elsewhere in Building 50. While the above conditions show an increased awareness of the hazard as time went on, the focus was still on sumps. In 2007, a contractor began work on a rectangular excavation in Building 50 of the UF6 Plant. The excavation was to house a new CTCW tank, which is desired


due to an increased number of cells. The new CTCW tank was to be placed in a concrete in-ground structure. The design specified double walled protection. As well, monitoring of the integrity of the tank was to be part of the new design and operation. On July 12, 2007, the contractor pulled a small tree root from the soil in the excavation. Liquid was noticed leaking into the excavation from the hole left by the tree root. The next day, the contractor noticed a yellow stain in the bottom of the excavation. The yellow stain was found on the surface of freshly poured concrete in the excavation. Cameco management were notified and began to investigate. Cameco immediately recognized that the yellow stain was associated with uranium. Cameco decided to voluntarily initiate a shut down of UF6 production operations and initiated an investigation into the source of uranium. Cameco promptly advised the CNSC and the MOE Spills Action Centre of the incident. The MOE Spills Action Centre notified Environment Canada. On July 19th, a complete plant shut-down was initiated. Subsurface contamination was confirmed in Building 50. Cameco initiated a formal investigation into the incident to determine causes and the extent of the contamination. Golder was contracted to carry out a comprehensive investigation. KnoW Problem Inc. and CJB Consulting Associates Inc. were contracted to carry out a root cause incident investigation.


4.0 CAUSAL FACTORS AND SUPPORTING INFORMATION 4.1 Causal Factor #1 – Some ‘floors, sumps & trenches’ are not designed to resist a

corrosive environment

Discussion of Causal Factor While the trenches in Cell Maintenance, the Effluent Room and the Flame Reactor area are lined with a chemical resistant coating, the Cell Room trenches are not. There was no design requirement identified to do so. Experienced personnel interviewed did not recall the trenches being much of a focus at all. While the design documentation is not specific, the intent of Cell Room trenches appears to be to collect small amounts of distilled water from leaks in the cells, and to hold the cell tempered cooling water return piping. When the UF6 plant was designed, not having a secondary barrier inside an operating plant was normal. The assumption was if you had a concrete floor, it would not be a problem. The construction aspects were discussed as a possible causal factor but the change from a monolithic floor in the Cell Room appears to have been appropriately handled with the installation of the water stops. Records associated with these types of construction changes were not found. Basis for Causal Factor

• While the design documentation is not specific, the intent of Cell Room

trenches appears to be to collect small amounts of water from leaks in the cells, and to hold the cell tempered cooling water return piping;

• Cell Room trenches not lined with a chemical resistant coating. No design requirement identified to do so;

• The two original tanks in the Pit were removed within a couple of years after the UF6 plant began to operate. This was completed in the fall of 1986. However, the Pit is coated with a chemical resistant liner;

• The trenches in Cell Maintenance, the Effluent Room and the Flame Reactor Area are lined with a chemical resistant coating;

• The area engineer removed some of the trenches in the Liquid Effluent Room. The plan was to fill in others over time;

• All process sumps are steel lined with a space between the concrete and the steel;

• Section 9.1 of the Lummus Engineering Specification # 9326-A-411 covering concrete material and construction for the UF6 plant states "Where indicated on the drawings, water stops shall be embedded in the concrete at joints";

• The failed construction joint at the east end of the East Cell Room is not specifically identified on the Lummus Design Drawings. This may have had an impact on the joint material used and the fact that a water stop was not used in the joint;


• A section of water stop material was found at a depth of 660 mm on the south side of the Core C1. Removing a small section of the trench wall adjacent to the location of Core C1 showed the water stop was installed parallel with trench wall and was located approximately 75 mm in from the surface of the wall;

• With respect to the trench in the Cell Room where one leak point was identified, Golder confirmed that the water stop does not continue across the construction joint at the wall and therefore there is a leak point at this location;

• Exposing the water stop also confirmed that the trenches in the Cell Room had been cast in two sections. The floor was cast first, then the walls. This construction may not reflect the intention of the construction drawings (Detail 9 of Drawing No. E9326-1 00108-L), which imply monolithic construction of the trenches. Failure to install the trench using a monolithic pour technique could create “cold joints” that could lead to small openings in the concrete structure, and that could provide focal points for attack by aggressive solutions;

• The floor of the effluent treatment area is coated, a portion of which had been covered with metal plating;

• A core was taken in the in-filled trench in the hallway leading by the Pit to the entrance to the effluent treatment area. It shows that the trench in that area was only about 75 to 100 mm deep, and was not lined;

• Regarding the Cell Room expansion, Spectrum Engineering Corp. Drawing No. 94014, titled Cell Room Relocation - Slab on Grade Sections, contains numerous specification notes. Note C9 states “Construction joints required by the contractor shall be approved by the engineer before construction. Construction joints in retaining wall on Line H shall include a 6 inch water stop”;

• Spectrum Engineering provided detailed specifications on the Cell Room Expansion, including detailed directions on how to install water stops. Lummus provided no equivalent detail for the original Cell Room. However, there were no specific instructions in the Spectrum Engineering documentation for a water stop in the vertical joint between the East and West Cell Rooms;

• Section 4.4.1 of the Lummus Engineering Specification # 9326-A-411 covering concrete material and construction for the UF6 plant states "expansion joint filler shall be preformed, non-extruding, resilient type conforming to ASTM D1751 unless otherwise specified on the drawings. Joints shall be sealed with rubber-asphalt joint sealer";

• Section 4.6.1 of the Lummus Engineering Specification # 9326-A-411 covering concrete material and construction for the UF6 plant states "water stop material shall be virgin, polyvinyl chloride, having a minimum depth of 4" and a multiple ribbed cross-section with a center bulb, "Sealtight" type number 4316 or equal";

• Section 405, pg 22 of the design manual states "Floor in the 300 area is rarely (almost never) washed down. Floor will be swept unless electrolyte


spilled." The 300 area comprises the Cell Room and Cell Maintenance areas;

• The June 2006 Safety Report (Issue 4) indicated that only some sumps (401FA14 (UF4 dryer), 35G18 and 51G106 (UO2 plant)) specify double lined, liquids not retained and solids regularly removed; and

• In the Environmental Aspects Registry, contamination of groundwater from sumps is only considered in the tote bin area. There is no reference to elsewhere in Building 50.

Interview Data - Recognizing that individual opinions and beliefs are subjective, and in some cases not factual, interviewees had a fair amount to say in this area. Most of it is quite consistent: • One interviewee involved in commissioning and early operation stated

“much time and effort was placed in the design of the concrete floors, trenches and sumps in the UF6 plant. Special, high density concrete was used. The type that would not crack and would be non-porous”;

• A Golder concrete specialist commented that the concrete in the Cell Room is good quality;

• Experienced personnel interviewed did not recall the trenches being much of a focus at all;

• When the UF6 plant was designed, not having a secondary barrier inside an operating plant was normal. The assumption was if you had a concrete floor, it would not be a problem;

• The original Pit design called for two tanks located within the Pit. One tank was to take the process fluid from Cell Maintenance. But there was too much sludge and it kept plugging up the tank. No way to remove the sludge once it plugged;

• One experienced person believed the trenches in the Flame Reactor Area were of the same design as those in the Cell Room, but did not present a problem. In fact, the trenches in the Flame Reactor area are coated, as per drawing requirements;

• Several interviewees commented that the main thing they tried to do with liquids is to keep them inside the building. They all thought "brand new building, we are contained";

• One interviewee involved in the design of the Cell Room extension stated “Water and electrical buses associated with the cells do not go well together. The only purpose for the Cell Room trenches is to channel water away from the electrical buses and to provide a channel to house the cooling water pipe below floor level”;

• When additional cells were added, the philosophy did not change. However, more detail was provided in the 1995 design specifications for the expansion; and

• The investigation team was aware that the June 1990 ERA proposed the long term plan for the Pit was to fill it with concrete and use an above ground tank. This was initially targeted to be done in 1993/94. The team


was told by a couple of senior interviewees that the priority level for this initiative has simply never reached the point where action has been taken. Essentially, it was considered ‘nice to do’ but not ‘must do’. Golder’s inspections of the Pit revealed that it was sound concrete with compressive strength above 36 MPa. There were two layers of chemical resistant lining on the bottom and one on the walls. There were no visible leak points from the Pit.

4.2 Causal Factor #2 – Liquid entering ‘floors, sumps & trenches’ is frequently

corrosive and attacks the structures

Discussion of Causal Factor It is generally acknowledged that corrosive chemicals have gone into the concrete structures over the years. Some of the structures, including the floors in Liquid Effluent and Cell Maintenance and the Liquid Effluent trenches, are designed to withstand corrosive chemicals (e.g. overflows from tanks). Other areas, such as the Cell Room trenches, are subjected to corrosive chemicals through process upsets such as ‘puking’ from the electrolytic cells and water balance problems that lead to back-flooding the trenches from the Pit. The Cell Room floors and trenches do not have a chemical resistant liner. Modifications to the Liquid Effluent trenches resulted in cross connecting these trenches with the Cell Room trenches and increased the frequency of their exposure to these chemicals.

Basis for Causal Factor Golder Report Findings • In the area where the South trench from the East Cell Room meets the N-S

trench, the surface of the floor slab exhibits deterioration similar to the walls of the trenches. It appears there may have been aggressive solution on this surface in the past;

• It appears that process liquids may have been spilled onto the unprotected floor areas of the Cell Maintenance Area;

• It appears that all of the Cell Room trenches exhibit varying degrees of surface deterioration from aggressive solutions and have delaminated surfaces in isolated areas. The joints at the ends of the trenches at the east wall are the most likely points where process liquids could leak out of the trenches;

• There is a clearly a visual distinction between the bottom half of the concrete and the top half of the concrete in original Cell Room trenches. The bottom half appears as though it has been attacked while the upper half appears fully intact. This is an indication of a “wicking type action” from chronic and corrosive wetness in the trenches; and

• According to a Golder concrete specialist, caustic solutions above 25% will attack concrete. The caustic solutions finding their way to the ‘floors, sumps & trenches’ over the years would be quite a bit lower in


concentration than 25%. As such, it is likely that mildly acidic solutions attacked the concrete.

Interview Data - Recognizing that individual opinions and beliefs are subjective, and in some cases not factual, interviewees had a fair amount to say in this area. Most of it is quite consistent: • There was no identified design requirement to deal with chemical

resistance treatment of some ‘floors, sumps & trenches’, in particular the Cell Room trenches;

• It is generally acknowledged that acid has gone into the trenches over the years. The acid sources are cell body failures and header pipe leaks;

• Dilute acid, probably from the electrolyte solution in the cells, pickles/attacks the concrete in the trenches;

• Cells fail and the electrolyte enters the cooling water, making it mildly acidic. This, in turn, attacks the cooling water pipes. Some failures have been experienced where the cell cooling water pipes connect (e.g. on the threads);

• Electrolyte spills from cells and the resultant cleanup is another way liquid in trenches can become corrosive;

• There is a sink right next to the failure point in the joint in the South Cell Room Trench. The sink is used by Operators to wash their sticks used to monitor cell levels. This is done 3 times per shift per cell and there are 54 cells. According to one interviewee, the sink is neutralized and dumped into the trenches. If there is any deviation in following the accepted neutralization practice, corrosive liquid may be released to the trench system;

• The Cell Maintenance area is used, in part, to dismantle cells for maintenance; and

• One employee interviewed suggested that a significant amount of sludge is produced by Cell Maintenance.

4.3 Causal Factor #3 –Uranium + chemicals frequently enter the ‘floors, sumps &

trenches’

Discussion of Causal Factor

Higher than anticipated volumes of process chemicals periodically entered the trenches and sumps as a result of operational problems. Process chemicals were routinely introduced into the structures from cleaning and scrubbing operations. Chemicals present in the process fluids would include uranium, fluorides, potassium hydroxide, arsenic, copper, and nickel. Subsequent design changes to address the problem of high liquid volumes may, in fact, have had unforeseen adverse consequences by introducing additional uranium and chemicals into the Cell Room structures.


Basis for Causal Factor • Right from start-up in 1984, floor sweepers cleaned the process floors in

the UF6 plant and were emptied into the N-S Trench just east of the Cell Room. The sweepers were discharged and rinsed out in close proximity to the CTCW Tank. It was easy for the floor cleaners to use this location as there was a hose nearby that they used to rinse out their machines;

• The idea was that this water would then go to the Pit; • Measured sludge sample results for uranium in nearby in-ground

structures are as follows:

o North Trench - Middle Section = 2,100 ppm o North Trench - East End (old Cell Room) = <40 ppm o North Trench - West End (new Cell Room) = 1,200 ppm o South Trench - West End (new Cell Room) = 2,100 ppm o South Trench - Middle Section = 10,600 ppm o South Trench - East End (old Cell Room) = 5,300 ppm o CTCW enclosure = 56,000 ppm

• A shallow trench was constructed between the Effluent Room and the North Cell Room trench early in the operation in an attempt to control water in the Effluent Room;

• The shallow trench from the Effluent Room provided a channel for additional uranium containing liquids to get into the Pit and the Cell Room trenches during water excursions. This was not recognized as an issue at the time the trench was constructed and used;

• Sump 405FA11 and the Effluent Room trenches, as well as the connecting trench between the Effluent Room and the Cell Maintenance Room were both filled in around 2000; and

• Tanks in the Effluent Room contain uranium in solution. By design, they occasionally overflowed to the floor. Initially, it overflowed to a trench in the Effluent Room. When this trench and sump were filled in with concrete in 2002, tank overflows were directed to the floor.

A relatively significant source of uranium to the ‘floors, sumps & trenches’ would have been the tanks, which by design, occasionally overflowed to the floor in the Effluent Room. A channel for uranium containing liquids from this tank to get into the Pit and Cell Room trenches was provided when a shallow trench was cut into the floor in the Effluent Room.

Interview Data - Again, recognizing that individual opinions, beliefs and recollections are subjective, and in some cases not factual, interviewees had much to say in this area. Most of it is consistent:


• Most interviewees were not surprised there was uranium found in the Cell Room Trenches. However, one key individual indicated he was surprised there is uranium in the Cell Room trenches;

• The area engineer made the decision to fill in the trench in the Effluent Room. He indicated it really didn't matter because conceptually, everything flows toward the Pit. That is what the PHA process concluded;

• Little grooves were then cut in the floor to help to channel the water toward the Pit;

• Believe the purpose of the shallow trench connecting the Effluent Room to the North Cell Room trench was to prevent water going out Door 16;

• The reason the area engineer filled in some of the trenches in the Effluent Room was because they could be leak paths. Secondly, it was physically very difficult to shovel sludge out of an 18" trench into drums;

• Filling in the trenches in the Effluent Room originated with the PHAs. A question from the PHAs was "how do you contain chemicals?" The answer was "the Pit";

• At one time, we used dirty KOH (i.e. KOH containing uranium) to neutralize cells in the Cell Maintenance Area;

• Pieces of equipment that would not fit in the wash tank in the Effluent Room would be hosed down on the floor. The residue would go to the Pit;

• Tank FB02 now overflows only a couple of times each year; • At one point, the trenches were all connected; • Have not seen the Pit fill with water and back flow into the trenches for

years; • Not easy to dump floor machines directly into the Pit. Easier to dump into

the trenches because there is a hose nearby to rinse the machine; • Floor machines from the Tote Room have been discharging there for 5 to 7

years. As long as they have had machines. In recent years, 25% discharged to the N-S Trench near the CTCW pump and 75% to the lined trench in the Cell Maintenance Room near the cell neutralization wash basins;

• On each occasion, 3 to 5 gallons of waste were discharged from each machine and then the machines were rinsed with a garden hose for 10 to 15 minutes;

• While the shallow trench was in use, the uranium concentrations coming to the N-S trench from the Effluent Room could have been elevated relative to those from the floor sweepers; and

• There were more waste streams than intended from the scrubbing circuit. 4.4 Causal Factor #4 – Liquid and sludge remain in the ‘floors, sumps & trenches’

for sustained periods of time


The water balance problems experienced in the early operation of the plant meant that the structures were subjected to more liquid than expected. When the water balance improved, some portions of the Cell Room trenches continued to hold the


effluents because of their construction. Although the intent was to grade/slope the trenches from west to east, some portions contained low spots and would retain effluents. In the case of the Cell Room trenches, the construction drawings required a maximum slope, which was met. The design did not specify a minimum slope. Also, the design of the CTCW tank installation and the Cell Room trenches did not allow for removal of trapped sludge.

Basis for Causal Factor

• The Pit provides storage for spills and overflows. With liquid spilling on

the floor and tanks in the Effluent Room overflowing, the liquid in the Pit would rise. When the Pit level became high enough, the liquid, bearing uranium and chemicals from the Pit, would flow back into the trenches in the Cell Room. This happened on several occasions;

• As reported in the 1990 Annual Report, the Pit was cleaned out during that year. When the Pit was cleaned, the sludge was found to contain 17% uranium and 1,153 ppm arsenic;

• The Cell Room trenches were not able to be cleaned because they had piping (between 4" and 8") running down their length;

• Whenever the return piping in the Cell Room trenches was replaced, the sludge and water was cleaned out from the trenches;

• The inter-space around the CTCW Tank was connected to the trench system. Once this became full of sludge, it could not be cleaned without removal of the Tank;

• Golder’s examination of the Cell Room trenches indicates the solution in the trenches may have pooled in places and did not flow through the trench as designed;

• During the coring of the south trench, it was noted that the coring water actually flowed a short direction west (up gradient) instead of east (down gradient) (Golder report);

• The apparent design intent was to grade/slope the trenches so that water flowed out. A Design Drawing Note states "all bottom of trenches to slope max. 1/16 in. in 12 in. u.n." This would result in a max elevation change of 10.25 in. over 164 ft. (No minimum slope is specified);

• Elevation measurements show the as built conditions for the Cell Room trenches have an average gradient of 1/32 in. in 12 in.;

• Elevation measurements made as part of the investigation indicate the slope of the trenches is variable. The actual survey data is shown in Appendix 3; and

• With the elevations as they are, fluids can be trapped in localized low points in the trenches.

Interview Data - Recognizing that individual opinions and beliefs are subjective, and in some cases not factual, interviewees had a fair amount to say in this area. Most of it is quite consistent:


• Several interviewees discussed the major imbalance of water in the beginning few years and their impression that more water coming in than could be handled or processed. This resulted in the ‘floors, sumps & trenches’ receiving and retaining a greater than expected volume of fluid. Some specific comments include:

o Couldn't turn the liquid around fast enough. Needed a repository

for the liquid; o We needed to work hard to get the UF6 plant to work. We needed

to figure many things out for ourselves, including how to control water;

o There were so many challenges associated with the UF6 plant in the beginning that effluent/water related problems were of lower priority;

o I definitely remember a few times when water overflowed out of Door 16 of the Effluent Room;

o All streams must keep looping through the Liquid Effluent Room. The challenge is managing the "water balance";

o We experienced plugging problems and this led to an abundance of liquid effluent. We had to bring in an extra tank to accommodate it;

o If an evaporator fails, you need to order in extra tankage immediately;

o Could get an overflow in Cell Maintenance if someone inadvertently leaves a steam hose on over the weekend;

o When you have a power failure, Operators attempt to get the chemical balance under control immediately. When that is done, then they can focus on effluent;

o The Manager of Production set up a Process Technology Group soon after commissioning of the plant with the purpose of getting the UF6 Plant to work better;

o We have better control of water now than with the original design. It used to be batch operation through the scrubber towers and now it is more continuous;

• The Pit became the “liquid safety net” once the two original tanks were

removed; • The trenches in the Effluent Room were cleaned out every summer

shutdown. We shovelled, into drums, the uranium that built up; • The Cell Room trenches didn't always have liquid in them but they would

have a little bit in them very often. Another person stated there was always water in the Cell Room trenches, which originated from various leaks in the process;

• The Effluent Room has historically been referred to as "the swamp" as it is always wet;

• There was definitely a build up of solids in all of the trenches;


• The current area engineer tries to reduce the sludge levels in the Pit to as low a level as possible and then pump it to the large tank in the Effluent Room;

• The trenches containing uranium sludge are back breakers to clean. They are cut to a depth of about 18 inches;

• The trenches and sump in the Effluent Room were filled in and now the floor is always wet. Operators were not happy about this;

• Don't think the Effluent Room was designed to have water on the floor. We started to have water issues after the sump and trenches were filled in;

• Berms were constructed on many external doors, including the large door (Door 16) at the north end of the Effluent Room;

• On occasion, the water in the Effluent Room gets above the berms and the "coping" and into the cement wall;

• The floor in the Effluent Building was always wet. No one was concerned. It was accepted practice; and

• The debris/sludge just pumped out of the Cell Room trenches was mostly rust and mud. It was not very heavy.

4.5 Causal Factor #5 – Some ‘floors, sumps & trenches’ deteriorated over time and

began to leak

Discussion of Causal Factor The extensive work conducted and reported by Golder identified and documented several locations where structures had deteriorated and potential leak paths for the uranium and chemicals were present. Some of the deterioration was due to the design (e.g. no lining for the Cell Room trenches). There were also instances of insufficient design detail, especially at the floor slab to wall joints. Where this joint was present in a trench, there was no specification for a water stop and thus the joint became a potential weak point. All structures are subject to deterioration with time. The severity of deterioration is subject to many conditions, such as environment (e.g. corrosive service), materials of construction and construction methods. Although there was some inspection of the sumps conducted by the production group and evidence of repairs to floors, there was no requirement for a preventive maintenance program associated with these structures because these structures were not identified as ‘floors, sumps & trenches’ or safety related.


• The PM program in place to check the condition of ‘floors, sumps &

trenches’ in the UF6 Plant was limited to the berms, checking of the sumps in the Effluent Room and the AHF unloading area trench; and


• There is evidence that repairs were done to the ‘floors, sumps & trenches’. However, it appears the repairs were carried out as needed and not as part of an overall PM program.

Golder Report Findings (August 30, 2007)

• The concrete trench in the Cell Maintenance Room that connects the two

trenches in the Cell Rooms (N-S trench) with the Pit is exhibiting considerable deterioration, especially the section where the excavation for the new CTCW tank was dug;

• Uranium concentrations in groundwater were elevated in all 12 boreholes in the Study Area relative to those of the external (RW series) Refinery Wells outside of the building;

• The highest concentration of uranium (445 mg/L) in a groundwater sample was collected from beneath the Cell Maintenance Room (Borehole BH50-2);

• Concentrations decreased with distance from the Cell Maintenance Room, decreasing to values of tens of milligrams per litre within approximately 20 m of this monitoring location;

• Inspections undertaken as part of the concrete assessment indicate the potential for leakage to the subsurface to have occurred from several locations and/or features within the Study Area in addition to the immediate vicinity of the excavation for the new CTCW structure;

• The groundwater monitoring data indicate general impacts beneath the Cell Maintenance Room, in the general vicinity of the Pit and concrete trenching just upstream of the Pit. After further investigation, Golder has found no evidence to suggest that there is a leak path from the Pit;

• Uranium and chemicals seep through the cracks and holes in the concrete, enter the soil and eventually migrate to the ground water below. This is a very slow process that could have gone on for years;

• Cores were taken from the floor of the N-S Trench in the Cell Maintenance Room to investigate cracking observed during the visual inspection;

• The trenches in the West Cell Room constructed in 1996 are in good condition;

• The trenches of the East Cell Room constructed in 1984 have exposed concrete surfaces. General loss of the concrete paste by aggressive solutions was noted in the lower half of the trenches due to exposure to process liquids, including dilute hydrofluoric acid;

• The severity of loss (scaling) on the trench walls varies depending on the height of liquid in the trenches over time. In general, the depth of loss into the concrete is about 10 to 30 mm;

• Delaminations (separations within the concrete) were noted in the concrete in the bottom of both trenches in the East Cell Room near the east end;

• The inspection indicates that there appears to be a joint between the trench floor and the trench wall at the east end of the East Cell Room. In several


locations, a piece of wire could be inserted up to approximately 75 mm into the joint;

• In transition from East Cell Room to the Cell Maintenance Area, construction joints exhibited considerable deterioration where the trenches meet the East wall of the Cell Room;

• A 150 mm diameter core was taken vertically on the north side of the south trench at the east wall through the joint. The core revealed that the joint is approximately 15 mm wide with the top 12 to 20 mm of the joint sealed. A metal rod could be inserted deep enough to reach underlying soil along most of the vertical length of the joint;

• The North Cell Room Trench was also cored in an area of a suspected delamination. Core C4 confirmed the presence of a delamination at a depth of approximately 65 mm. Examination of the cores obtained from the trenches indicates that the concrete below a depth of 60 to 75 mm appears to be sound and of generally good quality;

• Core C8, shown on Figure 4.11 was taken over a longitudinal crack near the south end of the trench. The core was advanced full depth through the slab and the crack extended the full length of the core. A soil sample was taken from below the C8 core location and was sent for analysis. The soil sample under core C8 showed a positive result for uranium of 16,000 ppm;

• One possibility is that the jack hammering for the new CTCW Tank may have created some of the damage (i.e. cracking of the concrete in the N-S Trench). However, Golder discounts this and indicates that the crack is not a new one;

• The CTCW concrete retaining structure that contained the cooling water tank exhibits some surface deterioration, but no cracking or delaminations. The grout layer on the bottom of the Pit was delaminated but the underlying concrete was sound;

• The trenches in the Cell Maintenance Room do not have any delaminations, but there is some minor chipping of the liner material along the top edges of the trenches in isolated areas;

• In summary, the N-S Trench that connects the two trenches in the Cell Rooms to the Pit is exhibiting considerable deterioration in areas and some of the cracks observed are the likely sources of uranium and chemicals leaking from the trench system into the soil;

• The visual inspection of the Pit indicated minor areas where the coating on the walls was missing, usually in relation to some piece of equipment that had been attached to the wall in the past;

• The floor topping in the Effluent Room is delaminated in sections, especially over the concrete in-filled trenches;

• The core taken in the in-filled trench in the hallway leading by the Pit to the entrance to the Effluent Room showed some evidence of deterioration in the concrete below the trench;

• A detailed condition survey was carried out on the in-ground trench in front of Door 16 in the Effluent Room. The concrete is delaminated and


spalled in the center portion of the trench to a depth of approximately 75-80 mm.;

• The concrete around a drain pipe leading under the slab from the trench at Door 16 in the Effluent Room into the filled in trenches exhibit considerable deterioration and the pipe was filled with material;

• With respect to the trench near Door 16 in the Effluent Room, it is Golder’s opinion that the evidence collected during inspection and testing of the floor trench in that location indicates that the trench contains structural cracks and joints. Again in Golder’s opinion, these cracks and joints would facilitate releases of fluids that may have been contained in the trench to the subsurface. There is visual evidence of uranium-containing precipitates within the structural features observed in the concrete and the soil beneath the trench contains elevated uranium;

• Cores taken from the floor slab near the north effluent drum dryer indicate the concrete is sound and the floor slab is approximately 200 mm thick;

• Based on the observations and measurements completed related to the steel sump linings in the Effluent Room, there is no evidence that these sumps have contributed to process liquid releases to the environment; and

• Reinforcing with concrete does not prevent concrete from cracking. The rebar essentially holds the concrete together when it does crack.

Interview Data - Again, recognizing that individual opinions, beliefs and recollections are subjective, and in some cases not factual, interviewees had some comments in this area. Most comments are consistent: • In the early 1990s in the Effluent Room, the area engineer noticed a

crack/hole in the floor, through which water was disappearing. The crack/hole was patched. The possibility was not recognized that the crack/hole may have already provided a path for uranium and other chemicals to reach the soil and water below the floor;

• Cell Room Operators really didn't notice the condition of the Cell Room trenches as they were behind the Cells and Operators didn't go back there very often;

• Because of the piping in the Cell Room trenches, it was not possible to inspect them;

• One interviewee recalled the walls and the floor of the Pit being resurfaced during one of the shutdowns. To do this, a contract company came in and cut out a big hole in the lid of the Pit (the investigation team was unable to find supporting documents);

• One interviewee recalled the Pit being cleaned and did not recall any cracks being found (the 1990 Annual Report references cleaning the Pit);

• One Golder concrete specialist stated that expansion joints typically have a service life. They do not last forever. There is no indication that the expansion joint found leaking had ever been inspected. There is no specific requirement for this in any design documentation;


• The same Golder concrete specialist indicated there was no such thing as a maintenance free structure; and

• The Golder concrete specialist indicated that the crack found in the bottom of the N-S Trench in the Cell Maintenance Room is not that large and could have been caused by any one of several factors (shrinkage, cold joint, etc.).

4.6 Causal Factor #6 – The monitoring program does not detect deterioration of

and/or leakage from the ‘floors, sumps & trenches’


The monitoring referred to actually consists of two types. The first is monitoring of the ‘floors, sumps & trenches’ for deterioration and potential leakage. This can take the form of planned and scheduled inspections or active leak detection with real time reporting. The second method is that offered by the groundwater detection system. In the latter case, the system will identify leakage long after it occurs. The ‘floors, sumps & trenches’ were not originally identified as safety related and thus there was no requirement for monitoring. Therefore, none was conducted. However, it is noted that over time the awareness of sumps and the Pit as potential leak sources was identified and some action taken. There is a formal groundwater monitoring program in place. This monitoring program was established during the siting and construction processes, leading to the development of the current program of Refinery Wells. A review of the correspondence suggests that the primary concern was protection of the nearby municipal water treatment facility. Early leak detection from Building 50 was not identified as being necessary. As early as 1983, it was recognized that the groundwater flow in this area is slow, which means that although it will take several years to detect a leak that has occurred from Building 50, there would be sufficient warning to initiate corrective action so as to limit environmental impact.


• There is no requirement, nor program in place, to inspect trenches, floors

or joints in Building 50; • However, as part of the PHA process, the area engineer was asked to

develop an NDE test to determine whether the sumps in the Effluent Room were leaking. The test was developed and the Effluent Room sumps were checked on an ad hoc basis;

• There is no requirement for on-line monitoring for leakage in the interspaces between the sump steel liners and the concrete;

• The 1990 Annual Report indicates that the Pit was cleaned. The liquid level in the Pit was visually monitored over the 3-month shutdown and did


not appear to change. The conclusion drawn was, if there are any leaks, they are small;

• An area engineer began checking sumps for leaks in the Effluent Room in 1993-94. By 2000, a leak test determined that sumps 405FA11 and 405FA01 needed to be removed from service. Upon sump liner removal, the leakage was determined to be by way of the carbon steel liner. No breach of the concrete chamber had occurred;

• An Environmental Risk Assessment document was issued in June 1990 (revisions in 1991 and 1993) and refers only to sumps and the Pit;

• The June 1990 ERA document details only one risk scenario related to this incident, namely a KOH/uranium leak from the Pit to the groundwater table. It is listed as a low probability scenario, caused by an undetected leak of used scrubber solution from the Pit which formerly contained tanks to handle cell maintenance waste waters and Cell Room ‘sumpage’;

• The June 1990 ERA lists current preventative measures for the leakage scenario from the Pit as follows: “Pit was probably not intended to continuously hold liquid. Bottom and part of side walls were acid-proofed in case tanks in the Pit failed. However, at present, no evidence of significant leakage. Liquid level likely above acid proofed section of side walls but is caustic, not acidic. Pit level monitored, no sign of steady level loss at present”;

• The June 1990 ERA lists Proposed Changes for the leakage scenario from the Pit as follows:

o Plan to inspect condition of concrete in 1993. Suspect Pit will need

to be steel lined in near future to ensure integrity. (Visual tests in 1990, 91 and 92 indicate Pit leaking very little if at all. Requires continued monitoring as a minimum);

o Should develop a testing method to prove the Pit and other area sump Pits do not leak significantly. (No definitive plans yet. Requires further action. Long term plan for the Pit is to fill it with concrete and use above ground tank 1993/94);

Golder has found no evidence to suggest that there is a leak path from the Pit. • The December 1997 Safety Report (Issue 1) states in the Process Hazard

Review portion for the Liquid Effluent Room that:

o “Hazards (1.3) - No regular QC inspection of process equipment.” This was accompanied by a recommendation to implement a non-destructive examination (NDE) program in this area. The investigation team found only one Work Order for some sump testing but the area engineer indicated he did periodic sump testing in the Effluent Room;

o “Hazards (8.1) - Leaks at sumps. Caused by: Corrosion (steel liners in sumps 405FA01, FA02 and FA11) or settling cracks at concrete Pit 302FA03.” The consequence is listed as contaminated


leakage into the ground. The safeguard listed is occasional inspections which tended to show that sumps do not noticeably leak;

• The June 2006 Safety Report (Issue 4) contains the following assertion:

o Sumps continue to be checked for leakage at least once per year by the area engineer;

• As part of the UF6 plant construction, eight RWs were installed around

Building 50 to protect the municipal water supply. These RWs have not yet detected any ground water contamination from Building 50 operations.


5.0 CORRECTIVE ACTION RECOMMENDATIONS CAR 1 - Cameco Port Hope needs to identify ‘floors, sumps & trenches’ as a safety related system because of the potential leak paths. This aspect must be reflected in the Safety Report and application of the quality assurance program. Appropriate design, construction and operating standard(s) and management change controls must be established and maintained. As a minimum, these must ensure that: a) ‘floors, sumps & trenches’ have chemical resistant surfaces where appropriate; b) ‘floors, sumps & trenches’ have double barriers, and monitoring between barriers for any chronically wet locations such as sumps or pits; c) any spills to ‘floors, sumps & trenches’ are promptly cleaned and/or neutralized; d) ‘floors, sumps & trenches’, and associated monitoring systems, are appropriately inspected and maintained; and e) procedures are written and implemented to ensure that no contaminated or corrosive liquids are deliberately discharged to ‘floors, sumps & trenches’ except where they have a chemical resistant liner. Causal Factor # and Description Root Cause Summary of Rationale for Root Cause

Design Spec NI Not all potential operating conditions in the Cell Room addressed by the design

No SPAC No SPAC for design standards Management of change NI

Not a safety related system so review not triggered; unknown if one carried out for many of the changes

1 - Some ‘floors, sumps & trenches’ are not designed to resist a corrosive environment.

Hazard Analysis NI

Unknown whether hazard analysis on ‘floors, sumps & trenches’ done at design; ‘floors, sumps & trenches’ are not on P&IDs and therefore not captured in Safety Report

No SPAC Not recognized as problem A&E lacks depth Trenches not recognized in Safety Report evaluations SPAC Incomplete Corrosive chemical spills should be neutralized, not specified in

instructions

2 - Liquid entering ‘floors, sumps & trenches’ is frequently corrosive and attacks the structures

No Procedure No written procedure for neutralizing sticks used to monitor cell levels 3 - Uranium and chemicals frequently enter the ‘floors, sumps & trenches’

No SPAC Not safety related system and no governing policy was in place

Design Spec NI Inadequate for CTCW tank and trenches A&E lacks depth PHAs for Safety Report did not identify the floors and trenches as leak

paths; not part of P&ID

4 - Liquid and sludge remain in the ‘floors, sumps & trenches’ for sustained periods of time. No SPAC Material remaining in trenches not recognized as a problem

Not safety related system, no SPAC for acceptable upkeep


CAR 1 - Cameco Port Hope needs to identify ‘floors, sumps & trenches’ as a safety related system because of the potential leak paths. This aspect must be reflected in the Safety Report and application of the quality assurance program. Appropriate design, construction and operating standard(s) and management change controls must be established and maintained. As a minimum, these must ensure that: a) ‘floors, sumps & trenches’ have chemical resistant surfaces where appropriate; b) ‘floors, sumps & trenches’ have double barriers, and monitoring between barriers for any chronically wet locations such as sumps or pits; c) any spills to ‘floors, sumps & trenches’ are promptly cleaned and/or neutralized; d) ‘floors, sumps & trenches’, and associated monitoring systems, are appropriately inspected and maintained; and e) procedures are written and implemented to ensure that no contaminated or corrosive liquids are deliberately discharged to ‘floors, sumps & trenches’ except where they have a chemical resistant liner. Causal Factor # and Description Root Cause Summary of Rationale for Root Cause

No SPAC Potential problem not recognized; no SPAC for awareness, maintenance or design Not safety related system; rationale for not requiring a PM would noot be documented

Specifications NI No maintenance criteria in design Management of change NI

Not restoring to original spec in repair/maintenance work (refers to floor in liquid effluent) Changes to trenches in liquid effluent

No PM Floor coating, trench, sumps etc not specified as a safety related system; rationale for not requiring a PM would not be documented

5 - Some ‘floors, sumps & trenches’ deteriorated over time and began to leak

PM NI No formal PM program Informal inspection by area engineer about 10 years, sumps only

Hazard analysis NI

Unknown whether hazard analysis on ‘floors, sumps & trenches’ done at design; ‘floors, sumps & trenches’ are not on P&IDs and therefore not captured in Safety Report

A&E lacked depth Evaluation through Safety Report did not identify issue. Not safety related system

SPAC not strict enough

Scope of groundwater monitoring was not intended for early detection

No SPAC No in-plant detection system for leaks; no inspection of structures

6 - The monitoring program does not detect deterioration of and/or leakage from the ‘floors, sumps & trenches’

Management of change NI

When the tanks were removed from Pit, the Pit should have been brought to the standard of other sumps

CAR comments – Cameco should ensure that inspection/maintenance instructions for the wells that have been installed and cores taken through


CAR 1 - Cameco Port Hope needs to identify ‘floors, sumps & trenches’ as a safety related system because of the potential leak paths. This aspect must be reflected in the Safety Report and application of the quality assurance program. Appropriate design, construction and operating standard(s) and management change controls must be established and maintained. As a minimum, these must ensure that: a) ‘floors, sumps & trenches’ have chemical resistant surfaces where appropriate; b) ‘floors, sumps & trenches’ have double barriers, and monitoring between barriers for any chronically wet locations such as sumps or pits; c) any spills to ‘floors, sumps & trenches’ are promptly cleaned and/or neutralized; d) ‘floors, sumps & trenches’, and associated monitoring systems, are appropriately inspected and maintained; and e) procedures are written and implemented to ensure that no contaminated or corrosive liquids are deliberately discharged to ‘floors, sumps & trenches’ except where they have a chemical resistant liner. Causal Factor # and Description Root Cause Summary of Rationale for Root Cause the plant are received from Golder.


CAR 2: Cameco Port Hope needs to carry out a design related assessment of credible acute and chronic challenges to ‘floors, sumps & trenches’ and then ensure their structural surfaces are appropriately designed. The designs must be developed as per an approved design standard to ensure requirements (e.g. PMs and maintaining as-built drawings) are clearly documented, communicated and implemented. Causal Factor Number and Description Root Cause Summary of Rationale for Root Cause

Equipment environment not considered

Acidic environment following process upset not considered

Confusing or incomplete (SPAC)

Design documentation lacks details for joints and trenches

No PM Not recognized as safety significant; no PM required

1 - Some ‘floors, sumps & trenches’ are not designed to resist a corrosive environment.

Drawings/ prints NI Discrepancies between the drawings and as-built conditions (e.g. cell room trenches)

2 - Liquid entering ‘floors, sumps & trenches’ is frequently corrosive and attacks the structures

Problem not anticipated Extent of release of chemicals was larger than design anticipated

3 - Uranium and chemicals frequently enter the ‘floors, sumps & trenches’

Problem not anticipated Overflows high enough to move liquid to other areas

4 - Liquid and sludge remain in the ‘floors, sumps & trenches’ for sustained periods of time.

Problem not anticipated Slope & pipe in trenches Liquid & sludge trapped in interstitial space CTCW tank


Equipment environment not considered

Presence of acidic and corrosive chemicals not in design

6 - The monitoring program does not detect deterioration of and/or leakage from the ‘floors, sumps & trenches’

Problem not anticipated Not anticipate a breach to this significance level

CAR Comments - When assessing the challenges, note that Cameco is installing sprinklers throughout the tower and this has potential impact.


CAR 3: Cameco Port Hope needs to implement an effective corrective action program so that problems are routinely identified and appropriate corrective action taken Causal Factor Number and Description Root Cause Summary of Rationale for Root Cause

Employee Feedback NI Floor sweeping and the acceptance of the swamp 3 - Uranium and chemicals frequently enter the ‘floors, sumps & trenches’ Employee

Communications NI Acceptance of the swamp


Corrective Action NI Early indication of leaks was not recognized as a pathway to the subsurface; did not realize significance

CAR 4: Cameco Port Hope needs to assess the adequacy of the groundwater monitoring program for early leak detection, and implement any necessary improvements Causal Factor Number and Description Root Cause Summary of Rationale for Root Cause 6 - The monitoring program does not detect deterioration of and/or leakage from the ‘floors, sumps & trenches’

Specifications NI Refinery Wells (RWs) only address the fence line, not immediate enough/real time.

CAR Comments – This assessment for ground water monitoring was done several years ago and at CNSC’s request was re-assessed again in late 1990’s and finalized in early 2000. The work was done by Golder.


APPENDIX 1 CAUSAL FACTORS - RELATIONSHIP TO EACH OTHER

AND THE UF6 PLANT SUBSURFACE CONTAMINATION INCIDENT


Some ‘floors, sumps & trenches’ are not designed to resist a corrosive environment Eldorado decides to

expand UF6 Plant Conversion Capability in Port Hope All ‘floors, sumps &

trenches’ are constructed to be appropriately chemical resistant

‘Floors, sumps & trenches’ are better protected and any chronic contaminants are contained in higher integrity structures

Liquid entering ‘floors, sumps & trenches’ is frequently corrosive and attacks the ‘floors, sumps & trenches’

Liquid entering ‘floors, sumps & trenches’ is either non-corrosive or is promptly neutralized and/or removed. Liquids may remain in double-walled structures with inter-space monitoring if appropriate

Liquid does not corrode the ‘floors, sumps & trenches’

ACausal Factor #1

Causal Factor #2


Chemicals in process fluids are generally not present at the secondary boundary so that there is no contamination potential of the ground

Liquid and sludge containing process fluids do not have a chronic presence in the ‘floors, sumps & trenches’, without there being primary and secondary barriers with inspection and/or monitoring of the barriers

B

A

Uranium and chemicals frequently enter the ‘floors, sumps & trenches’

Any chemical products entering ‘floors, sumps & trenches’ are promptly removed or they are contained within double protection with monitoring of the integrity of the primary barrier

Liquid and sludge remain in the ’floors, sumps & trenches’ for sustained periods of time

Any liquid and sludge quickly drains (or is cleaned) out of the ‘floors, sumps & trenches’, or it is contained within a primary barrier with monitoring of the integrity of that barrier so that the secondary barrier is not challenged

Causal Factor #3Causal Factor #4


Any weakness is prevented or promptly detected to prevent leak paths from developing

B

Some ‘floors, sumps & trenches’ deteriorated over time and began to leak

“Floors & sumps” are appropriately protected to resist deterioration and there are PMs in place to inspect and maintain their integrity

The monitoring system does not detect leakage from the ‘floors, sumps & trenches’

The monitoring system detects breaches in ‘floors, sumps & trenches’ where liquid may be routinely present before the concrete is challenged. “Floors & sumps” are maintained typically dry, and there are PMs to inspect and maintain their integrity so that any spills do not leak to the ground water/soil

Causal Factor #5

Advance warning provided and contamination is prevented from reaching the environment

Causal Factor #6

Subsurface contamination confirmed inBuilding 50


APPENDIX 2

SNAPCHART® OF EVENTS & CONDITIONS SHOWING WHAT HAPPENED LEADING UP TO THE SUBSURFACE

CONTAMINATION INCIDENT AT PORT HOPE UF6 PLANT ON JULY 13, 2007


E ld o ra d o m a ke s a p p lica tio nto AE C B fo r S ite Ap p ro va l o f

P o rt H o p e C o n ve rs io n Fa c i l i tyU F6 Fa c i l i tie s E xp a n s io n

E ld o ra d o m a ke s a p p lica tio n toAE C B fo r C o n s tru c tio n Ap p ro va l

fo r P o rt H o p e C o n ve rs io n Fa c i l i tyU F6 Fa c i l i tie s E xp a n s io n

L e tte r o f O c t 2 9 , 1 9 8 0

P rio r to th is , E ld o ra d o ca rrie do u t U F6 co n ve rs io n in th e

E a s t P la n t

L e tte r o f D e c 1 7 , 1 9 8 1

AL u m m u s ca rrie s o u t th e d e ta i le dd e s ig n o f th e U F6 P la n t

Fo cu s w a s p la ce d o ng a s e o u s a n d l iq u id

e m is s io n co n tro l a n dm o n ito rin g

N o e xp l ic i t d is cu s s io n o fb u i ld in g 'flo o rs , su m p s &

tre n ch e s '

G ro u n d w a te r m o n ito rin gp ro g ra m e s ta b l is h e d a sp a rt o f U F6 e xp a n s io n in

a d va n ce o f o p e ra tio n

Ta s k fo rce s e t u p too ve rs e e th e p ro je c t

Ta s k fo rce m a d e u p o fE ld o ra d o p e rs o n n e l top ro vid e o ve rs ig h t a n d

te ch n ica l in p u t to L u m m u s

L u m m u s d e s ig n a n d th eC o n s tru c tio n Ap p ro va l d o cu m e n ts

d id n o t co n s id e r th e tre n ch e s o rco n cre te flo o r a s a p o te n tia l le a k p a th

fo r u ra n iu m o r ch e m ica ls

P ro g ra m w a s in te n d e d to p ro te c tth e u n d e rg ro u n d s to ra g e ta n ks a t

th e m u n icp a l w a te r w o rks

Tre n ch e s , flo o rs , s u m p s a n dp its w e re n o t co n s id e re d to b e

s a fe ty re la te d


ALummus designs and

constructs the 'floors, sumps &trenches' in Building 50

B

Some 'floors, sumps &trenches' are not designed to

resist a corrosive environment

While the design documentation is notspecific, the intent of Cell Room trenchesappears to be to collect small amounts of

tempered cooling water from leaks in the cellsand hold the tempered cooling water pipes

Cell Room trenches not coatedwith a chemical resistant

substance. No design requirementidentified to do so

When additional cells were added in1996, the philosophy did not change.

All process sumps are steellined with a space betweenthe concrete and the steel

Experienced personnelinterviewed did not recallthe trenches being much

of a focus at all

Section 405, pg 22 of the designmanual states "Floor in the 300

area is rarely (almost never)washed down. Floor will be swept

unless electrolyte spilled."

Section 9.1 of the concrete designdocument states - "Where indicatedon the drawings, water stops shall beembedded in the concrete at joints."

The construction joints are typically described inLummus Design Drawings. This may have hadan impact on the joint material used and may bewhy a water stop was not used in the vertical joint

that was later found to have failed

Spectrum Engineering drawings on the CellRoom Expansion also do not specify a

waterstop at the vertical joint connecting theEast and West Cell Room trenches.

Trenches in Cell Maintenance, EffluentRoom and Flame Reactor area are lined

with a chemical resistant coating

The floor of the effluent treatment areais coated, a portion of which had been

covered with metal plating

CF1

Pit is coated with achemical resistant liner

Golder found nowater stop used in

the failed vertical joint


First UF6 Plantoperating activities

on April 2, 1984

C

When the UF6 plant was designed, not having asecondary barrier inside an operating plant wasnot unusual. The assumption was if you had a

concrete floor, it would not be a problem

CF1

During the current investigation, aGolder concrete specialist

commented that the concrete in theCell Room is good quality

BLummus completes

design documentation forEldorado in1983

The Operations QualityAssurance Manual, which applies

to safety related systems, tookeffect at the same time

UF6 plant iscommissioned

'Floors, sumps & trenches' werenot considered part of a safety

related system

No records for anycommissioning related to'floors, sumps & trenches'


UF6 Plant experiencesnumerous operating

problems

Water balance problemsresult in Pit flooding on

several occasions

Right from the beginning andIn all parts of the process,

including liquid effluent

"There were so many challengesassociated with the UF6 plant in thebeginning that effluent/water related

problems were of lower priority"

Being the low point, Pit is primarycollector for excess fluid. Volume

experienced during operation is greaterthan design expectations

DC

Original design included two tankslocated in the Pit to take the process

fluid from Cell Maintenance.

Sludge from Cell Maintenance keptplugging the tanks. Difficult toremove the sludge from tanks

Process Technology Groupis set up in 1985

One of the focuses was toget the UF6 Plant to operate

more effectively

Members of the group wereinvolved during design and

commissioning

Pit flooding results in fluid backingup into the unlined Cell Room

trenches. Necessitated use of anoutside tank at times


The functionality of the Pit, as primarycollector, was extended to include what

had been the influent to the tanks

Tanks and pump removed andfull cover plate is placed on top

of the Pit by fall 1986

Shallow Trench is cut to join theEffluent Room trench to the North

Cell Room trench early in theoperation of Building 50

Purpose of the trench is to provide a path for liquidfrom excursions in the Effluent Room to reach the

Pit. Also directs flow away from Door 16

No formal design change carriedout as this system is not considered

a safety related system

D E

"The Effluent Area hashistorically been referred to as"the swamp" as it is always wet"

Decision made to removetwo tanks and associatedpump in the Pit made in

December, 1984

Connecting the Effluent Room trenches tothe N-S trench unintentionally introducesadditional uranium into the Cell Room

trenches and the Pit

This shallow trench, was later filled in forergonomic reasons at the request of

Operations


Liquid enters 'floors, sumps &trenches', including Cell

Room trenches

FE

Liquid entering 'floors, sumps &trenches' is frequently corrosive

and attacks the structures

During the current investigation, Golder foundthat unprotected concrete 'floors, sumps &trenches' in the study area exhibit signs of

deterioration from aggressive solutions

Golder states "In the area where the south trenchfrom cell rooms meets the north-south trench, the

surface of the floor slab exhib its deteriorationsimilar to the walls of the trenches. It appears

there may have been aggressive solution on thissurface in the past"

Dilute acid, probably from the electrolyte solutionin the cells, neutralization of the sticks used to

monitor cell levels and/or the acid wash station inLiquid Effluent, pickles/attacks the concrete and

any joints in the trenches

Cell cooling coils fail and the electrolyte entersthe cooling water, making it mildly acidic. This, in

turn, attacks the cooling water pipes. Somefailures have been experienced where the cell

cooling water pipes connect (e.g. on the threads)to the main header in the trench

Electrolyte spills from cells and resultantcleanup is another way liquid intrenches can become corrosive

There is a clearly a difference in appearancebetween the bottom half of the concrete and the tophalf of the concrete in original Cell Room trenches.

The bottom half appears as though it has beenattacked while the upper half appears fully intact. This

is an indication of a "wicking type action" fromchronic and corrosive wetness in the trenches

Neutralization solution used to wash the sticksused to monitor cell levels is discharged into

the trench. No written procedure. Could becorrosive if not done properly

Large equipment washing on the floor near thetrenches would direct fluids to the trenches


Six inch high berm in front ofDoor 16 in the Effluent Room is

repaired in October 1990

Formal PM on thenorth door berminstituted in 2003

Eldorado/Cameco makesprocess improvements in

the UF6 Plant.

Several interviewees confirmed that "We havebetter control of water now than with the original

design. It used to be batch operation through thescrubber towers and now it is more continuous"

GF

A leak of processfluids/effluent out ofBuilding 50 occursthrough Door 16 on

October 7, 1990

Cameco Corporationpurchased the assets of

Eldorado, including the PortHope conversion facility,effective October 5, 1988


Uranium and chemicalsfrequently enter the 'floors,

sumps & trenches'

Discharge location in closeproximity to the CTCW Tank

because of availability of water toflush the equipment

Easy for the floor cleanersto empty their machines

at this location

Widely known and an acceptedpractice. Likely contributed tosome of the uranium in the

sludge in the Pit and the trenches

HG

Right from start-up in 1984, floorsweepers cleaned the process

floors in the UF6 plant and emptiedtheir machines into the N-S Cell

Room trench

Sludge sample results for this investigation for uranium inCell Room containment structures are as follows:

1. North Trench - Middle Section = 2,100 ppm2. North Trench - East End (old cell room) = <40 ppm

3. North Trench - West End (new Cell Room) = 1,200 ppm4. South Trench - West End (new Cell Room) = 2,100 ppm

5. South Trench - Middle Section = 10,600 ppm6. South Trench - East End (old Cell Room) = 5,300 ppm

7. CTCW enclosure = 56,000 ppm

Shallow trench from Effluent Roomprovided a channel for additional

uranium containing liquids to get into thePit and Cell Room trenches during water

excursions. No records of thisinstallation have been located

Because of the operations,most interviewees were not

surprised there was uraniumfound in the Cell Room

trenches

Also, pieces of equipment that wouldnot fit in the wash tank in the EffluentRoom would be hosed down on thefloor. The residue would go to the Pit

At one point, the trencheswere all connected

By design, tanks containing uraniumoccasionally overflow to the floor in the EffluentArea. When shallow trench was constructedand the area dykes were removed, there wasan increase in the frequency of the spread of

liquid

When the Pit was cleaned in1990 the sludge was foundto contain 17% uranium and

1,153 ppm arsenic


UF6 Plant continues to experienceoperating challenges , includ ing

occas ional m ajor liqu id overflowsinto 'floors, sum ps & trenches '

L iqu id and s ludge rem ain in the 'floors, sum ps & trenches ' for

s us ta ined periods of tim e

I

At tim es , the Pit would partly floodto the extent that its overflow would

flood the North and South CellRoom trenches

The Cell Room trenches were notable to be cleaned becaus e they had

pip ing (between 4 in . and 8 in .)running down the ir length

H

Golder exam ination of the CellRoom trenches ind icates "the

solution in the trenches m ay havepooled in p laces and d id not flowthrough the trench as designed"

During the coring of the s outh trench,Golder noted "the coring water actua lly

flowed a short d irection west (up gradient)instead of east (down gradient)"

The Cell Room trenches wereonly ab le to be cleaned when

the Cell Tem pered CoolingWater p ip ing was changed out

Trenches appear to be s lopeds uch that liqu id flows in to themand is unable to fu lly dra in out.

The apparent des ign in tent was to s lope the trenches s o that waterflowed out. A Des ign D raw ing Note s tates "all b ottom of trenches to

slope m ax. 1 /16 in . in 12 in . u .n ." Th is would res ult in a m axelevation change of 10.25 in . over 164 ft. (No m in s lope s pecified)

Elevation m eas urem ents s how the as built conditions for the Eas tCell Room trenches have an average gradient o f 1 /32 in . in 12 in .

The d ifference between the h ighes t and lowes t m eas ured e levationsin the South trench in the Eas t Cell Room is approxim ate ly 5 in .

There are loca lized low points inboth the North and South

Trenches that m ay be partly froms urface deterioration

The trenches in the Eas tand Wes t Cell Room s areroughly 50 and 36 m etresin length (164 and 118ft)

CTCW tank des ign traps liqu idand s ludge in in ters titia l s pace

between the tank and theconcrete

Pit had s ludge and liqu id leve lfor extended periods of tim e

Effluent Area trenches conta ineds ludge and liqu id and were

frequently cleaned out foroperational reas ons


Sludge contaminatedwith uranium builds upin the North and SouthCell Room trenches

Operations cleans outsludge in the Cell Room

trenches on a fewoccasions over the years

Whenever the piping in the trenchesis changed out or repaired whichallows access to the bottom of the

trench for cleaning

This appears to havetaken place a few times

since 1984 start-up

JI


Some 'floors, sumps &trenches' deteriorated over

time and began to leak

A very s low process thatappears to have gone

on for years

Uranium and chemicals seepthrough weakened locationsin the concrete, enter the soil

and s lowly migrate

J

"Inspections undertaken as part of the concreteassessment indicate the potential for leakage to

the subsurface to have occurred from severallocations and/or features within the Study Area in

addition to the immediate vicinity of the excavationfor the new CTCW containment structure"

"The groundwater monitoring data indicategeneral impacts beneath the Cell

Maintenance Room, in the general vicinityof the effluent pit and concrete trenching

just upstream of the effluent pit"

"A 150 mm diameter core was taken vertically on thenorth side of the south trench at the east wall through thejoint. The core revealed that the joint is approximately 15mm wide with the top 12 to 20 mm of the joint sealed. Ametal rod could be inserted along most of the vertical

length of the joint deep enough to reach underlying soil"

"The trench running north-south that connects the twotrenches in the cell rooms to the effluent pit is exhib iting

considerab le deterioration in areas and some of thecracks observed are the likely sources of contaminants

leaking from the trench system into the soil"

"The concrete around a drain pipe leadingunder the slab from the trench at the NorthDoor in the Effluent Room into the filled in

trenches exhib its considerab le deterioration"

In the current investigation,Golder, contracted to carry out acomprehensive study, make the

following observations:

CF5

"The CTCW concrete retaining structurethat contained the cooling water tank

exhib its some surface deterioration butno cracking or delaminations"

"The grout layer on the bottom ofthe pit was delaminated but theunderlying concrete was sound"

K


The PM program in place to check thecondition of 'floors, sumps & trenches' in the

UF6 Plant was limited to the berms, checkingof the sumps in the Effluent Room and the

AHF Unloading Area trench

A Golder concrete specialist stated that expansionjoints typically have a service life. They do not lastforever. There is no indication that the expansion

joint found leaking had ever been inspected.There is no documented requirement for this in

any design documentation

There is evidence that repairs were done to theconcrete floors & sumps. However, it appearsthe repairs were carried out as needed and not

part of an overall PM program

CF5

K L


Deterioration in the concretetrenches and floors, for themost part, went undetected

Cell Room Operators indicated theydidn't notice the condition of the trenchesas they were behind the Cells, there is asteel grate on top and Operators did not

go back there very often

Because of the piping in the CellRoom trenches and the heavy trench

covers, it was not easy to inspect them

Some repairs are carried out onan individual basis

Safety Report (Issue 4) in June, 2006indicated that only some sumps (401FA14

(UF4 plant), 35G18 and 51G106 (UO2 plant))specify double lined, maintained dry and

solids regularly removed

In the Environmental AspectsRegistry, contamination of

groundwater is only considered fromsumps in the tote bin area. There isno reference elsewhere in Building

50

The above conditions show an increasedawareness of the hazard as time goes on.

However, the focus is still on sumps.Floors and trenches are still not identified

as a potential leak path

No requirement was specified forinspection in the design or safety

documentation

The monitoring program doesnot detect deterioration ofand/or leakage from the 'floors, sumps & trenches'

CF6

L M


NM

There is no program inplace to inspect trenches

The 1990 Annual Report indicates that thePit was cleaned. The liquid level in the Pitwas visually monitored over the 3 monthshutdown and didn't appear to change.

The conclusion drawn was, if there are anyleaks, they are small

As part of the PHA process, the area engineer wasasked to develop a NDE test to determine whetherthe sumps in the Effluent Room were leaking. He

developed such a test and the Effluent Roomsumps were checked on an ad hoc basis

An area engineer began checking sumps for leaks inthe Effluent Room in 1993-94. By 2000, a leak test

determined that sumps 405FA11 and 405FA01needed to be removed from service. Upon sump linerremoval, the leakage was determined to be by way of

the carbon steel liner. No breach of the concretechamber had occurred

The June, 2006 Safety Report (Issue 4)contains the following statement:

"Sumps continue to be checked for leakageat least once per year by the area engineer"

The June, 1990 ERA lists current preventativemeasures for the leakage scenario from thePit as follows: "Pit was probably not intendedto continuously hold liquid. Bottom and part ofside walls were acid-proofed in case tanks in

the pit failed. However, at present, noevidence of significant leakage"

"Liquid level likely above the acidproofed section of side walls but is

caustic, not acidic. Pit level monitored,no sign of steady level loss at present"

As part of the UF6 plant construction, eightrefinery wells were installed around

Building 50 to protect the municipal watersupply. These RWs have not yet detected

any ground water contamination fromBuilding 50 operations

June 1990 ERA proposed that the Pit befilled in and replaced with an above

ground tank as a precautionary measure

CF6


Contractor beginswork on a rectangularexcavation in Building

50 of the UF6 Plant

7/12/2007

Contractor pulls asmall tree root from

the soil in theexcavation

Contractor notices ayellow stain in the

bottom of the excavationthe next day

Excavation to house anew CTCW Tank

A larger CTCW Tankdesired due to an

increased number of cells

New CTCW tank to beplaced in a concretein-ground structure

Fluid noticed leakinginto the excavationfrom the hole left by

the tree root

Cameco managementnotified and begin to

investigate

Cameco immediatelyrecognizes the yellow stain is

associated with uranium

Yellow stain found onthe surface of freshlypoured concrete in

the excavation

ON

Design specified doublebarriers and monitoring

April, 2006 inspection ofCTCW tank indicates it

would need to be replacedwithin a few years

Cameco decides to advancethe schedule and replace the

CTCW tank in 2007


7/13/2007

Cameco decides to voluntarilyinitiate a shut down of UF6

production operations

Cameco initiates a formalinvestigation into theincident to determine

causes and extent

Cameco initiates aninvestigation into thesource of uranium

Cameco promptly advisesCNSC and the MOE Spills

Action Centre of the incident

MOE Spills Action Centrenotifies Environment Canada

Golder contracted to carry outa comprehensive investigation

KnoW Problem Inc. and CJB ConsultingAssociates Inc. contracted to carry out a

root cause incident investigation

OSub-surface

contaminationconfirmed inBuilding 50

Existing monitoringwells do not detect

contamination in thegroundwater from

Building 50

Contamination hasnot migrated to the

RW wells

On July 19th, a complete plantshut-down was initiated


APPENDIX 3

ELEVATION DATA FOR TRENCHES IN THE STUDY AREA

ATTACHMENT C TapRooT® Investigation Report Subsurface Contamination Incident … · 2020-04-01 ·...

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