American Nuclear Society (ANS) Hyatt Regency … Nuclear Society (ANS) Risk-Informed Standards...

American Nuclear Society (ANS) Risk-Informed Standards Committee (RISC)

Meeting Minutes June 17, 2009

Hyatt Regency Atlanta Hotel Members present: Allen Camp (RISC Chair), Sandia National Labs; Robert Budnitz (RISC Vice Chair), Lawrence Berkeley National Lab; Paul Amico*, SAIC; Robert Bari, Brookhaven National Lab; Richard Black, US DOE; Mary Drouin*, US NRC; David Finnicum, Westinghouse; John Gaertner (P/T**), EPRI; Dennis Henneke*, General Electric; Rick Hill, ERIN; Gene Hughes, ETRANCO; Greg Krueger*, Exelon; Stanley Levinson, AREVA NP; Patricia Schroeder, ANS; Jonathan Young, Pacific Northwest National Lab Alternates present: Victoria Anderson (for Biff Bradley), NEI; Ching Guey* (for Ken Kiper), FPL; Doug Hance (for John Gaertner), EPRI; David Johnson (for Don Wakefield), ABS Consulting; Gareth Parry*, NRC Observers, liaisons, and guests present: Nate Bixler, Sandia National Labs; Sarah Chisholm, Duke Energy; Kent Gebetsberger, AREVA NP; Prasad Kadambi (SB Chair), Individual; Mark Linn, Oak Ridge National Lab; Charles Moseley (NRMCC Co-chair), Individual; Doug Paul, Duke Energy; Mark Rutherford, AREVA NP; Grant Teagarden, ERIN *participated by phone ** (P/T) = attended part time

1. Roll Call and Introductions Roll call was taken and introductions were made. A quorum was established. 2. Approval of Agenda The agenda was approved as presented. 3. Meeting Key Issues and Objectives RISC Chair Allen Camp reviewed the agenda and summarized the intent of the meeting. 4. RISC Chair’s Report – Attachment A A. Summary of Standards Board Meeting Allen Camp summarized his written report provided to the Standards Board the previous day. A copy of the written report (Attachment A) was distributed to members. He explained that a new group was formed jointly managed by the National Institute of Standards and Technology (NIST) and the American National Standards Institute (ANSI) to coordinate standards activities. The new group was called the Nuclear Energy Standards Coordinating Collaboration (NESCC). Dick Black explained that the U.S. Department of Energy (DOE) found that there were a lot of standards outdated that would be needed for construction of new plants. DOE anticipated supporting this effort with funding. The first NESCC meeting was held June 1, 2009, at NIST. Support from the U.S. Nuclear Regulatory Commission (NRC) was also recognized.

2

Mary Drouin questioned whether the NESCC would conflict with the Nuclear Risk Management Coordinating Committee (NRMCC). Black explained that the NESCC was broader than the NRMCC and did not intend to conflict with the NRMCC already in existence. Black reported that participants included representatives from the American Concrete Institute (ACI), ANS, American Society of Mechanical Engineers (ASME), American Society of Testing and Materials (ASTM), Institute of Electrical and Electronic Engineers (IEEE), American Welding Society (AWS), Electrical Power Research Institute (EPRI), DOE, and NRC. NESCC membership was expected to grow. Black stated that inventory of standards that supported nuclear facilities was available on ANSI’s website. Camp reported that the Standards Board approved balance of interest reports for all consensus committees. New definitions for balance of interest categories were approved and would be implemented once approved by ANSI. B. Grant Camp stated that he believed the grant from the U.S. Nuclear Regulatory Commission to support the Lower Power Shutdown (LPSD), Level 2, and Level 3 standards projects had been approved for three years. Stanley Levinson requested for ANS to provide working group chairs details on the grant and reimbursement mechanism, etc., when available. C. Nuclear Risk Management Coordinating Committee (NRMCC) Activities Camp reported that the last NRMCC meeting was in March 2009. RISC and ASME’s Committee on Nuclear Risk Management (CNRM) provided reports to members of the NRMCC. Camp stated that the NRMCC was updating their strategic plan. Camp explained that ASME sent a letter to NRC followed by an ANS letter to the NRC. The letter emphasized support for risk-informed approaches in the regulatory process and credit for past success. Additionally the letter expressed a concern that either the NRC or industry might begin to move away from risk-informed processes and encouraged NRC and industry to work together to find a solution. Mary Drouin stated that the NRC discussed the letters but hadn’t decided whether a response was required. D. Training PRA Analysis Standard (SB Action Item 11/08-08) Camp explained that he was assigned an action item by the Standards Board to determine whether ANS should get involved in activities to train industry to comply with ANS PRA standards. Stanley Levinson added that training would become important as current working group members would not always be available. Camp asked for volunteers to provide the following:

1) A one-pager on whether a standard or guidance document on complying with the LPSD, Level 2, and Level 3 standards were needed, and

2) A one-pager on whether a training program to comply with the LPSD, Level 2, and Level 3 standards were needed.

3

Dennis Henneke acknowledged that there were many questions when using the fire PRA standard. He felt that the commentary in the standard helped but additional clarification was needed. Rick Hill volunteered to lead an ad hoc committee with Mary Drouin, Dave Finnicum, and Stanley Levinson to examine the need for a standard and training on complying with the LPSD, Level 2, and Level 3 standards. Finnicum speculated that by the time you get a standard on training done, the need would no longer exist. Action Item 6/09-01: Rick Hill to lead a group with Mary Drouin, David Finnicum, and Stanley Levinson to prepare 1) a one-page white paper on whether a standard or guidance document on complying with the LPSD, Level 2, and Level 3 standards was needed, and 2) a one-page white paper on whether a training program to comply with the LPSD, Level 2, and Level 3 standards was needed. REPORT @ NEXT MEETING Levinson clarified that ASME LLC’s training was not on the “how to” but included only “what” the supporting requirements meant. Drouin noted that the LLC had been reaching out to the appropriate experts to train regardless of standard developing organization affiliation. Camp stated that presently the LLC was operating independently of RISC. Members of the committee informed Camp that Mark Reinhart was no longer with the International Atomic Energy Agency (IAEA). Mary Drouin suggested that a new IAEA liaison be solicited. Camp asked Drouin to initiate an invitation with her contacts. Action Item 6/09-02: Mary Drouin to attempt to find a new IAEA rep to replace Mark Reinhart. E. CNRM Activities Bob Budnitz reported that the last CNRM meeting was held in February 2009 which he reported during the RISC March 24, 2009, conference call. No additional meetings were held.

5. Update on Joint Committee/Reorganization Allen Camp explained that progress had been slow on creating a joint ANS RISC/ASME CNRM committee. He felt that it would take a long time to truly merge the two committees. At present both consensus committees would continue activities as usual. Camp stated that he would like to create a combined executive committee. The concept was discussed at the Standards Board (SB) meeting. The SB requested that individuals from the RISC on the executive committee representing ANS be ANS members. A formal motion was conducted that passed with one negative from Don Spellman, the SB Vice Chair. Spellman’s negative was due to the exclusion of IEEE on the executive committee. Drouin expressed her disappointment in the delay but recognized that the process to merge the two consensus committees was complicated. Hughes suggested that RISC should meet once a year away from ANS meetings and invited ASME CNRM to join. Camp confirmed that plans to meet with CNRM were in the works. Camp requested that RISC members endorse him and Bob Budnitz as the ANS representatives on the

4

combined executive committee with the potential of one or two additional members to be appointed in the future. The following motion was made: MOTION:

To endorse Allen Camp and Robert Budnitz as the ANS representatives on the combined ANS/ASME Executive Committee.

The motion passed unanimously. Camp stated that he would contact Rick Grantom to schedule an ANS/ASME Executive Committee meeting by the end of July. Action Item 6/09-03: Allen Camp to schedule an ANS/ASME Executive Committee meeting with Rick Grantom by the end of July. 6. Qualitative Standards Ad hoc Committee Report – See Attachment B A white paper entitled “Recommendations from the Working Group on Qualitative vs. Quantitative PRA Methods” from the Qualitative Standards Ad hoc Committee was distributed prior to the meeting. The ad hoc committee, chaired by Rick Hill, included members Bob Bari and Gene Hughes. The paper provided the charter of the group, background information, definitions, status of methods in standards, potential roles for qualitative methods, and recommendations for RISC consideration. The group’s recommendation was to use qualitative tools in the LPSD standard and to include wholly when incorporated into the Level 1 combined standard and that separate standards were not needed for qualitative and quantitative methods. Committee members expressed differing opinions. While many members completely agreed with the recommendations, a few felt that qualitative methods should not be included in a probabilistic risk assessment (PRA). Mary Drouin stated that the NRC would not endorse seismic margin assessment in the LPSD PRA standard in RG 1.200 but would consider it for endorsement elsewhere. Allen Camp suggested a vote on the follow three questions:

1) Do we endorse the two roles and acknowledge the fact that there are things that can be done that are less than a full PRA in the development of a PRA?

The committee was affirmative with one abstention by Mary Drouin.

2) Definition of PRA

Because the definition of a PRA would need a lengthy discussion, Camp requested to take this question off line and engage ASME if necessary. He recommended that RISC support the definitions in the combined standard with comments to be sent to him.

5

Action Item 6/09-04: RISC members to provide Allen Camp comments regarding the need for a new definition of PRA.

3) Do you believe in the future (not retroactive) we should have these types (qualitative) of methods integrated in the same document OR documented separately?

Committee members were polled individually for their thoughts on including qualitative methods in future standards. The following comments were expressed: Paul Amico: Didn’t think that any were self-contained. Felt that they were part of the documentation of the risk associated with the plant. Since they support the risk profile of the plant, they should be included in standards as they are developed. Mary Drouin: (from NRC perspective) Standards should be a technically-based PRA so that when an application was submitted, they did not have to use their resources to do detailed review of the PRA; would only need to focus on the application. Qualitative methods are fine but should be in a separate document. Dennis Henneke: From a writer’s perspective, he would like to see them included when methods overlap. Greg Krueger: As a user, he would want to keep everything consistent and would want them combined for convenience and with consistent definitions. Ching Guey: Echoed what Krueger said; believed it was practical to include in one document.

Bob Bari: To the extent that alternative methods supported the intent of the PRA, methods should be kept in one document. However, self-contained methods should not be an alternative when PRA methods existed. Jon Young: Agreed with Bari; stated that when qualitative methods supported quantitative methods, they should be in one document. If they were self-contained, they should not be included. Dave Finnicum: Felt that self-contained methods were of value but recognized Drouin’s philosophy and that the NRC might not endorse. Stanley Levinson: Agreed with Bari and Young. Felt that if methods needed to be used in concert, they would be most valuable in one document. Doug Hance: Felt that the paper from the Qualitative Standards Ad hoc Committee was valuable. Stated that whatever method was needed, it should be included in one document. Rick Hill: Stated that his thoughts were provided fully in the paper.

6

Gene Hughes: Stated that he agreed with many. Felt that it was unworkable to be exclusionary when you don’t know the particulars of future needs. Victoria Anderson: Agreed with the majority that it needed to be easy for the user.

Allen Camp: Recognized Hill, Bari, and Hughes for their efforts on the ad hoc committee and preparing a paper on qualitative vs. quantitative PRA methods. Camp cautioned that as we go forward, attention be paid to make the technical level as high as possible and not fall into traps that qualitative or simpler procedures have used. He felt that a price could be paid in the future if short cuts were legitimized.

Gareth Parry questioned “V. Role 1” on the paper presented by the ad hoc committee. He felt that the sentence should be modified to delete the portion of sentence after the word “site.” Members were in agreement. Rick Hill was requested to finalize the “Recommendations from the Working Group on Qualitative vs. Quantitative PRA Methods” paper for the record. Action Item 06/09-05: Rick Hill to finalize the “Recommendations from the Working Group on Qualitative vs. Quantitative PRA Methods” white paper for the record. 7. Status of Standards Writing Group Activities A. External Events Pilot Update – See Attachment C John Gartner provided a progress report on the seismic portion of the external events pilot project which had been in works for almost a year. The intent was for the lessons learned to be incorporated into the standard. Gartner stated that EPRI did a significant amount of work to redo the hazard estimates for the central and eastern United States for new nuclear power plants. It was felt that the new estimates provided better science and results. Gaertner noted that it was believed that the hazards were higher today. Seismic fragility was found to be non-conservative and required a new building response model. The pilot showed that the old Diablo PRA was good. EPRI committed to produce a new human seismic interaction guide for risk assessment. A second guideline EPRI committed to undertake was on relay chatter. Mary Drouin asked whether the pilot had NRC representation. Action Item 6/09-06: John Gartner to find out if NRC staff was involved (or will be involved) in the EPRI seismic pilot and provide information to Mary Drouin. Gaertner reported that much attention was paid to resolving fragility issues, and an updated EPRI fragility report would be issued in 2009. Additionally, an industry workshop was anticipated to be held in January 2010 to provide the final results and recommendations of the pilot. Dave Finnicum informed members that he would be pulling together a group to perform a peer review of the seismic pilot project. He questioned whether the results from the pilot study would be publicly available. Stanley Levinson suggested that if portions of

7

the pilot study results were confidential, a second document be prepared with non-confidential information available to the public. Action Item 6/09-07: John Gaertner to let EPRI know that there was interest for a publicly available document on the results of the seismic external events pilot. B. Level 2 / ANS-58.24 Allen Camp provided a report of the Level 2 standards project. He noted that development had been largely on hold waiting for word on the NRC grant. Camp stated that he would like to see a draft of ANS-58.24 to RISC prior to the November meeting for preliminary review. C. Level 3 / ANS-58.25 – See Attachment D Keith Woodard provided a status report to RISC. Previous meetings were summarized as well as conference calls. Woodard was satisfied with the makeup of the working group. Although members were very busy, assignments were getting completed. Woodard stated that the working group was resolving issues with applying the three capability categories format. Once NRC grant funding was finalized, Woodard anticipated holding a lengthy meeting to complete the draft. He projected that a preliminary draft could be available for RISC review by November 2009. Camp asked if any guidance was needed from RISC. Levinson felt that the working group should take a shot at the categories for consideration by RISC. Camp suggested that the RISC might need an additional day to meet in November if preliminary Level 2 and Level 3 drafts were available prior to the meeting. Woodard confirmed that the two groups were working together. D. LPSD PRA / ANS-58.22 Qualitative Risk Assessment (QLRA) Methods – See Attachments E & F Doug Hance provided members a presentation on Capability Indices for Qualitative Risk Assessment Technical Elements (Attachment E). He provided a review of capabilities categories for the ASME PRA Level 1 standard, differences between QLRA capability indices and capability categories, and a comparison between three and one capability indices for QLRA. Hance explained that the term “indices” was used in place of “categories” to distinguish QLRA. Much time was spent discussing the benefits and negatives of one capability index verses three capability indices. Hance reported that the working group recommended using three capability indices for QLRA. The following motion was made:

Motion: To endorse the recommendation of the working group to move forward with three categories but to consider a term clearly different than capability categories.

The following vote was documented:

8

APPROVED (10) OPPOSED (5) Paul Amico Allen Camp Victoria Anderson (for Biff Bradley) Mary Drouin Bob Bari Dennis Henneke Bob Budnitz David Johnson (for Don Wakefield) David Finnicum Jon Young Doug Hance (for John Gaertner) Rick Hill Gene Hughes Greg Krueger Stanley Levinson The motion passed 10 to 5 with the direction to the working group to proceed with three capability indices (appropriate term to be determined). Hance also provided a presentation on Shutdown Configuration Risk Management (Attachment F) that included the history of EPRI reports from 1989 to 2000, goals, and long-term trending. He also provided a summary of NUMARC 91-06. Other LPSD / ANS-58.22 Issues Bob Budnitz, a working group member standing in for the absent WG chair Don Wakefield, reported that the ANS-58.22 LPSD Working Group met in San Diego in February of 2009. It was the first physical meeting in four years. He felt that the face-to-face meeting was huge in moving forward. The working group was debating controversial comments. Unfortunately, some members had not completed assignments, but commitments were made to complete assignments in the summer for working group review so that the draft could be finalized and resubmitted to RISC in October for another reballot. Budnitz stated that all comments would receive a written explanation unless noted accepted. Budnitz would confirm anticipated dates for release for completion of comment responses and the revised draft. Action Item 6/09-08: Robert Budnitz to check on anticipated dates for the completion of comment responses and the revised draft to aid in scheduling committee review and meeting discussions. Hance added that for the qualitative portion of the LPSD standard, they focused on industry comments and felt that three capability categories would resolve the issues. 8. Recommended Practice for Boiling End State with Core Damage in LPSD Allen Camp stated that a discussion was added to the agenda at the request of Gene Hughes as he would like for a requirement for boiling end state with core damage to be included in the LPSD standard. Hughes stated that boiling was often used, and he felt that it should be included in risk assessment. Bob Budnitz stated that the LPSD working group did not disagree with the technical content of the boiling end point write up that Hughes provided but that they felt it should not be a requirement. Stanley Levinson added that if you wanted to add requirements on boiling to the LPSD standard, he felt that it would be acceptable if it was appropriate for your application.

9

Budnitz questioned on whether using boiling could be added to an appendix, but Hughes felt it would lessen its significance. Hughes offered to rewrite the text. Action Item 6/09-09: Gene Hughes to provide Pat Schroeder proposed text to the LPSD standard on boiling for distribution to RISC for comment. Camp requested that a conference call with Hughes be held in August 2009 to discuss this further with Don Wakefield and Bob Budnitz. Action Item 6/09-10: Allen Camp, Don Wakefield, and Robert Budnitz to participate in a conference call with Gene Hughes to discuss adding a requirement on boiling to the LPSD standard. 9. Other Business A. Ad Hoc Committee on Developing Non-RISC PRA Standards Bob Budnitz reported that he supported a discussion at the Standards Board meeting on ANS standards developed without support from members of the RISC or CNRM. Budnitz believed that these working groups needed support from the community of PRA experts. He recommended an intermediate option of working with the other ANS consensus committee chairs to see whether there was a role that RISC could support. The level of support might need to depend on the number of standards projects and could vary on a case-by-case basis. The path forward should be for each ANS consensus committee to provide a list of standards that might benefit from risk-informed, performance-based insights. Budnitz stated that NFSC Chair Carl Mazzola had already provided a list, and he agreed to be the point person to coordinate this effort. Rick Hill recommended an alternative. He speculated that a working group chair may not be aware that the project could benefit from being risk informed. Hill suggested that a RISC member review a PINS form when in the approval process. Action Item 6/09-11: Pat Schroeder was requested to modify the PINS form to indicate whether risk-informed, performance-based methods will be used. Camp stated that the other consensus committee chairs were favorable to RISC support. Budnitz stated that N16 Chair Calvin Hopper speculated that some members of the nuclear criticality safety standards community might not be receptive. Paul Amico recommended to identify opportunities to risk inform standards. Budnitz agreed but felt that there was a greater priority to identify potential risk-informed, performance-based standards currently in development. Camp suggested that Budnitz check with John Gaertner to participate in this effort. B. Future Role of RISC; Where do we go next? When questioned, RISC members made the following suggestions for future committee activities:

10

• To consider information in decision making and in regulatory, defense in depth. • A guidance document on how to integrate the risk documents. • In the future, may want to consider large release and digital control. • A standard on digital Instrumentation and Control. • Other technical issues to support the standards we currently have. • How are we going to deal with the Level 2 and 3 standards when published? • What to do with advanced reactor standards activity?

Members questioned whether ASME’s draft standard on advanced light water reactors had been made available for comment. Stanley Levinson offered to check with ASME. Action Item 6/09-12: Stanley Levinson to provide Pat Schroeder ASME’s advanced LWR PRA draft for RISC when available. 10. Next RISC Meeting Members were informed that the November RISC meeting could potentially be lengthened to two days. 11. Adjourn The meeting was adjourned at 4:21 p.m. (eastern).

RISC Progress Report June 2009

Publication ANSI/ASME/ANS RA-S-2008, “Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications,” was published in December 2008. ANSI/ASME/ANS RA-Sa-2009, “Addenda to ASME/ANS RA-S-2008, Standard for Level 1/Large Early Release Frequency Probabilistic Risk Assessment for Nuclear Power Plant Applications,” was approved 2/2/2009 and published in April 2009. This “addendum” is actually an entirely new version, meaning that the entire 2008 version has been replaced by this version. Action Completed The RISC was provided an opportunity to comment on the ASME draft standard for Probabilistic Risk Assessment for Advanced Non-LWR Nuclear Power Plant Applications. The RISC was provided an opportunity to comment on NFSC draft standard ANS-53.1-20xx, “Nuclear Safety Criteria and Safety Design Process for Modular Helium-Cooled Reactor Plants.” Grant Awarded for RISC PRA Standards An NRC grant to support the RISC PRA standards has been awarded. Verbal confirmation has been received. Formal confirmation with contract details will be forthcoming. In RISC Ballot/Vote (or resolving comments) ANS-58.22-20xx, “Low Power Shutdown PRA Methodology”

• Writing group led by Don Wakefield • Reballot issued due to substantive changes • Reballot closed October 2008 with 674 committee comments and 116 public

comments • Revised draft to be issued for a third ballot before the end of 2009

Standards in Progress ANS-58.24-20xx, “Severe Accident Progression and Radiological Release (Level 2) PRA Methodology to Support Nuclear Installation Applications”

• Writing group led by Mark Leonard, underway since 2005 • Development to be expedited with grant funds • Preliminary draft for RISC review in 2010 • Ballot date to be determined

ANS-58.25-20xx, “Standard for Radiological Accident Offsite Consequence Analysis (Level 3 PRA) to Support Nuclear Installation Applications”

• Writing group led by Keith Woodard, underway since 2005 • Development to be expedited with grant funds • Preliminary draft for RISC review in 2010 • Ballot date to be determined

Other Issues

• Committee has not yet reached consensus on how to treat “qualitative” methodologies in its “PRA” standards

• Coordination with NRMCC and ASME-CNRM • Combining ANS RISC with ASME CNRM

pschroeder

Text Box

Attachment A

Recommendations from the Working Group on Qualitative vs. Quantitative PRA Methods

May 27, 2009 (Edited 6/17/09)

I. Charter: The charter for the working group is to recommend a framework by which qualitative standards and quantitative methods can be addressed in future ASME and ANS Probabilistic Risk Assessment (PRA)1 standards so that these standards can support risk-informed decision-making. II. Background RISC and others have been struggling with how certain methodologies (e.g., SMA for seismic risk standard, FIVE for fire risk standard and the qualitative part of the low power and shutdown risk standard) fit into the framework of risk standards. The Working Group on Qualitative vs. Quantitative PRA Methods (WGQQPM) realizes and recognizes that there is not universal understanding and agreement on concepts and definitions on this topic. Central to this topic are the following questions: 1) When is an analysis PRA? 2) What is a qualitative analysis? 3) What is the distinction between a qualitative analysis and a quantitative analysis? 4) What are the defining characteristics of an analysis which, when applied to a

decision-making process, make that decision risk-informed? 5) Does qualitative mean non-quantitative? In order to define some distinctions, the following table may be useful:

PRA & Quantitative

Non-PRA & Quantitative

PRA & Qualitative

Non-PRA & Qualitative

It is now possible to try to populate each box in this table with specific examples of methodologies and/or analyses. Also, we could attempt to put pieces of our risk standards into these boxes. The following sections provide some Definitions, Status of Methods in Standards, Potential Roles for Qualitative Methods, and Recommendations for RISC Consideration. III. Definitions

A. PRA • The ANS Glossary is being revised and the proposed definition for PRA

(there was not one in the past) is, “Probabilistic risk assessment (PRA)

1 Probabilistic Risk Assessments (PRA) are also referred to as Probabilistic Safety Assessments (PSA).

pschroeder

Text Box

Attachment B - revised per direction at 6-17-09 meeting.

technology provides a quantitative assessment of nuclear power plant accident risk. Models delineate the [note that some words are missing here in the text of the draft glossary, possibly the word “operation”] of systems and operators response to accident initiating events. Additional models identify component failure modes required to cause the accident mitigating systems failure. Nuclear power plant PRA data analysis estimates the parameters used to determine the frequencies and probabilities of the various events modeled in PRA. (ANSI/ANS 53.1-200x Draft)” However, the most recent draft of ANSI/ANS 53.1 defines PRA to be, “A qualitative and quantitative assessment of the risk associated with plant operation and maintenance that is measured in terms of frequency of occurrence of risk metrics, such as the frequency of a radioactive material release and its effects on the health of the public [also referred to as a probabilistic safety assessment (PSA)].” These definitions express the opinion that PRA can be qualitative or quantitative in the assessment of risk.

• The IAEA glossary defines PSA as probabilistic safety assessment (PSA) as “A comprehensive, structured approach to identifying failure scenarios, constituting a conceptual and mathematical tool for deriving numerical estimates of risk.”

• IAEA Requirements document Safety of Nuclear Power Plants: Design,

NS-R-1, is the base design document for nuclear power plants sort of like ANS-51.1 is for PWRs, ANS-52.1 is for BWRs, and ANS-53.1 is for HTGRs. This IAEA document in section 5.73 identifies a mixed bag of elements (listed below) for probabilistic safety analysis to be carried out in order: 1. to provide a systematic analysis to give confidence that the design will

comply with the general safety objectives; 2. to demonstrate that a balanced design has been achieved such that no

particular feature or postulated initiating event (PIE) makes a disproportionately large or significantly uncertain contribution to the overall risk, and that the first two levels of defense in depth bear the primary burden of ensuring nuclear safety;

3. to provide confidence that small deviations in plant parameters that could give rise to severely abnormal plant behavior (‘cliff edge effects’) will be prevented

4. to provide assessments of the probabilities of occurrence of severe core damage states and assessments of the risks of major off-site releases necessitating a short term off-site response, particularly for releases associated with early containment failure;

5. to provide assessments of the probabilities of occurrence and the consequences of external hazards, in particular those unique to the plant site;

6. to identify systems for which design improvements or modifications to operational procedures could reduce the probabilities of severe accidents or mitigate their consequences;

7. to assess the adequacy of plant emergency procedures; and 8. to verify compliance with probabilistic targets, if set.

This list of elements can be accomplished with either qualitative or quantitative methodologies. • ASME standard

Probabilistic risk assessment (PRA) is defined as,:”A qualitative and quantitative assessment of the risk associated with plant operation and maintenance that is measured in terms of frequency of occurrence of risk metrics, such as core damage or a radioactive material release and its effects on the health of the public.”

B. Risk

Risk is typically recognized as a formulation of the product of likelihood (probability) and consequences. More generally, it can be a probability vs. consequence plot or an array of probability vs. related consequences (for a particular event or an aggregate of events)

C. Risk-Informed

NRC has defined risk-informed in several places; e.g., • COMSAJ-98-003, February 20, 1998, from NRC Chairman Shirley

Jackson • NUREG-1614, Strategic Plan • NRC glossary • March 11, 1999 Commission White Paper on Risk-Informed and

Performance-Based Regulation The NRC definitions all tend to have their genesis from what is in the white paper, i.e.,

Risk-Informed Approach: A "risk-informed" approach to regulatory decision-making represents a philosophy whereby risk insights are considered together with other factors to establish requirements that better focus licensee and regulatory attention on design and operational issues commensurate with their importance to public health and safety. A "risk-informed" approach enhances the deterministic approach by: (a) allowing explicit consideration of a broader set of potential challenges to safety, (b) providing a logical means for prioritizing these challenges based on risk significance, operating experience, and/or engineering judgment, (c) facilitating consideration of a broader set of resources to defend against these challenges, (d) explicitly identifying and quantifying sources of uncertainty in the analysis (although such analyses do not necessarily reflect all important sources of uncertainty), and (e) leading to better

decision-making by providing a means to test the sensitivity of the results to key assumptions. Where appropriate, a risk-informed regulatory approach can also be used to reduce unnecessary conservatism in purely deterministic approaches, or can be used to identify areas with insufficient conservatism in deterministic analyses and provide the bases for additional requirements or regulatory actions. "Risk-informed" approaches lie between the "risk-based" and purely deterministic approaches. The details of the regulatory issue under consideration will determine where the risk-informed decision falls within the spectrum.

In addition, the NRC in Regulatory Guide 1.174 states that PRA quality needs to be “commensurate with the application for which it is intended and the role the PRA results play in the integrated decision process.” The NRC makes no explicit determination of qualitative or quantitative risk tools. In addition, conventional language would suggest that “risk-informed” would be any decision where the conclusion of the decision is “informed” not necessarily “based entirely” on information that comes from a “risk” study. Thus “risk-informed can be from qualitative or quantitative sources and the NRC allows both.

D. Summary Qualitative risk methods for risk-informed decision-making are methods (primarily non-numerical, but sometimes supported by numerical information) that identify specific attributes of probability and consequences to provide information to make decisions. Quantitative risk analysis methods for risk-informed decision-making are methods (primarily numerical) that determine with some appropriate degree of exactness (i.e. with related estimates of uncertainties) the quantities of attributes of probability and consequence to provide information to make decisions.

E. Conclusion Given the above definitions, all the methods employed currently in the nuclear industry to estimate risk are quantitative to a certain degree. The industry has used the term qualitative to apply to some quantitative methods as a means of distinguishing between degrees of resolution of results accuracy. In both qualitative and quantitative methods the measures of risk, probability, and consequences should be the same. The distinction comes in translating the measures into metrics. For quantitative methods the metrics are numerical. For qualitative methods they are non-numerical (e.g. linguistic metrics like high, medium, and low). The following section summarized the methods endorsed in the current PRA standards.

Thus qualitative is a special case of quantitative; a first step in any quantitative PRA that is done right. For a qualitative analysis to be the basis for risk-informing, it should be the best that one can reasonably do, in term of likelihoods and consequences. It should recognized dependencies to the extent possible and it should give a clear statement of uncertainties in both likelihoods and consequences, even if these are presented in terms of qualitative descriptors or linguistic variables (e.g. H, M, L).

IV. Status of Methods in Standards:

• Full Power Internal Events: The ASME standard endorses more quantitative methods; however, section 3.6 does endorses and provides examples of supplementary methods stating, “These supplementary analyses will depend on the particular application being considered, but may involve deterministic methods such as bounding or screening analyses, and determinations made by an expert panel.”

• External Events: The standard deals with all external events, but the focus in on seismic. SMA takes a prominent role in the standard but there is a caveat that requires enhancements (provided in Appendix D) to allow SMA to play that role.

• Fire: The standard contains a non-mandatory appendix discussion on FIVE but does not explicitly endorse its use; however, the Fire PRA process described in NUREG/CR-6850 includes both quantitative and qualitative screening tasks. In fact, the whole approach of NUREG/CR-6850 is a process that limits the extent of detailed fire modeling by a series of qualitative and quantitative screening steps.

• LP/SD: This standard is in draft; however, the decision was made by ANS RISC to allow the use of qualitative methods in the standard as a screening method to determine if further quantitative analysis is needed. This decision will not be revisited as part of this Working Group effort.

V. Potential Roles for Qualitative Methods:

Role 1 Use qualitative methods as analysis tools equivalent with quantitative methods when the need for technical adequacy of quantitative methods is not required or supported by data. This is justified when the risk contributor is judged to be low for the existing design and site. Role 2 Use qualitative methods as screening tools to judge if risk is significant enough to require further evaluation with more quantitative means. This approach is an extension of screening techniques already employed in quantitative risk assessments. Initial screening should be performed in all risk assessment to separate the insignificant from what remains to be analyzed in detail. Note that a degree of “significance” must be predetermined by the analyst. It effectively establishes a metric for the underlying measure.

Formatted: Indent: Left: 18 pt

Formatted: Bullets and Numbering

Formatted: Indent: Left: 18 pt

Formatted: Bullets and Numbering

Deleted: or when the uncertainties are so large that subject matter experts are unable and/or unwilling to quantify the degree of uncertainty

The difference between role 1 and 2 is that role 1 means a judgment of low risk or very large uncertainty already exists and the qualitative tool is necessary to gain risk insights. Role 2 is employed when the qualitative tool can do an adequate job of screening risk scenarios at a low enough level to justify that quantitative tools are needed only for analysis of the higher risk scenarios. As noted above, quantitative approaches may be difficult where uncertainties a large and difficult to quantify.

VI. Recommendations for RISC Consideration: In the Background section, five questions were posed. These questions have been answered. The following two recommendations are for the consideration of the ANS RISC. A. The Use of Qualitative Tools in the Combined Standard (ASME/ANS RA-S-

series) The purpose of the combined standard is to combine the existing standards without changing any technical elements or judgments. Thus, the combined standard must incorporate all the methods already employed in the individual standards.

B. The Use of Qualitative Tools in the Future Integrated Standard

At some time in the future, having gained experience with the combined standard and resolved some technical integration problems, an integrated standard will be produced. This standard may include other risk contributors such as fires during shutdown. Roles 1 and 2 are appropriate for incorporation of qualitative tools in to PRA standards.

Seismic PRA at Surry

A Pilot Application of the External Events PRA Standard

John Gaertner, EPRIJune 17, 2009

For:R.P. KassawaraG. S. HardyD.L. Moore

2© 2009 Electric Power Research Institute, Inc. All rights reserved.

Pilot Project of ANS Seismic PRA Standard

• Original Comments on ANS Standard Approach from Industry– The Standard is written with some ambiguity so that conformance with

each capability category is uncertain• One goal of the Pilot project is to provide further guidance on how to

conform to the capability category II– Cost may not be reasonable

• At the completion of the pilot, better insights on the required costs will be available

• Fragilities? System models? HRA? Hazards?

– Seismic Hazard in particular is a moving target

• Pilot project will explore the seismic hazard

requirements

pschroeder

Text Box

Attachment C


Seismic Hazard Use in SPRA

• Original Seismic Hazard Issue from Industry– Standard requires new hazard unless clear case can be made that

existing hazard is accurate or conservative– NRC expects conservative extrapolation of hazard curves at high g

levels– Seismic hazard still in research mode

• Four different interpretations for the Charleston Seismic Source Zone were presented at the 2006 USGS CEUS workshop

• Current Pilot Plant Status on Seismic Hazard– New seismic hazards have been conducted for New NPP sites– EPRI has conducted new hazard estimates for CEUS existing NPP

locations that can be used for Capability Category II SPRA studies (such as the Pilot for Surry)


Seismic Hazard Comparison – Old to New


Surry Uniform Hazard – Old vs New

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.1 1 10 100

Solid = Update; Dashed = Orig.

1E‐5

GMRS

1E‐4

1E‐4

1E‐5

GMRS

Frequency


Plant Logic Model

• Existing Surry SPRA Plant Logic Model– Very small number of components in existing model due to

screening of components (surrogate elements utilized)

• Surry Pilot Review– Plant logic model being increased to improve accuracy and since

former screening criteria not valid due to increased seismic hazard

– Updating model to reflect plant changes since original IPEEE study


Seismic Fragility Challenges for Pilot Plant

• Non-conservative screening criteria (due to lower hazard) used for existing SPRA– New component screening and walkdown have been

conducted• Existing seismic response no longer valid for new

hazard– New probabilistic response being conducted for 2

buildings and scaling of response being conducted for remaining buildings

– Significant costs in this area, scaling accuracy being studied as part of this Pilot

• Full relay chatter evaluations not conducted for existing SPRA– Pilot project reviewing options to cost-effectively include

relays into the SPRA (systems and fragility screening)


Pilot Seismic PRA by ANS Standard Tasks

• Task 1 - Review of Current Surry PRA and Comparison to ANS Standard Capability Category II Criteria

-- Completed• Task 2 – Seismic Hazard Development,

Plant Logic Development and Seismic Fragility Development– Seismic Hazard and Site Response

Completed– Probabilistic Structural Response – Aux

Bldg Completed– Surry Site Walk down Completed

• Task 3 – Integration of Seismic Hazard and Seismic Fragility and Generation of Final Project Report


Human Interactions Guide

• ANS Standard is Vague on Seismic HRA– Not a consensus on approach within SPRA community– Eventually a standardized seismic HRA Calculator desired

• Provides:– Background and review of previous seismic human interaction

methods– General seismic HRA considerations– Examples from Past SPRAs (Diablo, Krsko, San Onofre,

Columbia, EDF)• Surry specific method

– Incorporation of seismic event impacts on operator actions from internal events PSA

– Development of seismic-unique operator actions (such as relay chatter recovery)


Relay Chatter Systems Guidance

• Objective is to maximize use of existing Surry A-46 relay chatter evaluation, and EPRI relay chatter methodology documents, but reduce resources required to incorporate relay chatter into seismic PSA

• Addresses relay chatter in systematic and comprehensive manner• Guidance identifies critical relay chatter scenarios to limit detailed

evaluations to specific equipment and associated relays (systemsimportance and timing screening)

• Provides identification of potentially significant relay chatterscenarios for:– Relay fragility analysis– Operator recovery actions


Upcoming Systems Tasks

• Relay chatter evaluation• Human reliability analysis• Seismic initiating event tree and associated fault trees

• Systems screening of seismic failures to incorporate into CAFTA model

• Later tasks include the quantification of CDF and LERF, and the uncertainty and sensitivity analyses


Key Challenges/Innovations of ANS Pilot Implementation

• NRC Review and Comments– Dominion management desired NRC participation– NRC not available early, so participation deferred to

after first complete result• Best Estimate of Structural Response

– Best estimate, upper bound and lower bound analyses for two buildings

– Estimate the effects of probabilistic response– Develop scaling factors for remaining buildings


Key Challenges/Innovations ANS Pilot Implementation (Cont)

• Service Building SSI Analyses– Structurally connected to

the Turbine Building– Embedded foundation

requires use of SASSI– Incoherence analyses

require development of stable transfer functions

– Soil sites require much more effort



• Screening of SSEL and Development of Fragilities from Screening Process– NP 6041 SMA screening tables used during walkdown– Anchorage and load path need assessment in parallel– Two Issues found with development of fragility

1. HCLPF 84 approach within Fragility Guide incorrect2. Spectral acceleration screening in conformance unclear



• Special meeting to resolve fragility issues in January– Kennedy, Campbell, Hashimoto, Merz, Tong, Hardy– Modern UHS incorporates peak to valley variability

• Double counting to include additional PTV variability• HCLPF50 appropriate for screening level

– In-structure spectral acceleration levels associated with 6041 screening not consistently applied in past

• Note for table specifies 2g screening level; basis unknown• Level revised to 1.8 g which correlates to 1.5 times the 1.2 g

ground spectral acceleration stated for tables• Update to EPRI fragility report in 2009


Potential Sensitivity Studies

• Correlation• Screening Levels• Aleatory Uncertainties


Surry ANS SPRA Pilot Schedule

Task Description Completion DatePlant Seismic Logic Model Update SSEL – May 2009

Finalize Plant Logic Model – July 2009Seismic Fragilities Seismic Response Aux Building – Jan 2008

Seismic Response Control / Service Building – May 2009Scaling for Other Buildings – Early June 2009Seismic Fragilities – August 2009

Risk Quantification, Final Report

Quantification – October 2009Final Report – December 2009

Industry workshop around January 2010 EPRI NPC meetings to review final evaluation and insights

on SPRA Standard application

1

MEETINGS

• 2nd Full Meeting held at MIT during Boston ANS June 2007

• 3rd Full Meeting Held During ANS Winter Meeting In Washington DC

• 4th Full Meeting Held in Anaheim During ANS Annual Meeting June 11, 2008

• 5th Meeting Held in Reno at Winter ANS Meeting November 12th, 2008

• Conference Call held Feb 12th—Moderately Successful

MEMBERSHIP

• All Subject Areas in the Consequence Standard are Well Represented

• Well Rounded Group—Having Trouble Completing Draft Writing Assignments

• More than Half Have Expressed Concern about Funding to Attend Meetings

• Expect Good Turnout for Atlanta Meeting• Sarah Chisholm & Carl Mazzola have Joined

Group and are Participating Actively. • Have not Heard from Mr. Bexon from UK.

pschroeder

Text Box

Attachment D

2

WORKING GROUP ASSIGNMENTS• Overview---(Woodard*, O’Kula, Levinson, Mitchell)**• Level 1/2 Interface--- (Paul*/Chisholm, Leaver)• Probabilistic Framework/Uncertainty ---(Johnson*,

Levinson)• Site/Plant Input Data---(Teagarden*)• Dispersion---(Woodard*)• Dosimetry---(O’Kula*)**• Health Effects---(Mubayi*)**• Economic Factors (Mubayi*)**• Reporting of Results, Quantification (Teagarden*,

Johnson)• Models (Codes), Example Cases----

(Chisholm*,Teagarden, Mitchell)• *Indicates Lead Author• **Indicates Sections with Second Drafts Due

EXPENSE COMPENSATION ISSUES• We Are Continuing to Have About 50%

Representation Meetings. There Have Been Conflicts With Other ANS Meetings on Wednesdays. Continue to think Wednesdays are Best

• Some Employers Have Agreed to Fund WG Members’Participation. We Have Been Able to Justify Attendance by Scheduling During ANS Meetings

• If We Had Travel Expense Allowances Meetings Could be Scheduled at Different Times & Venues Without Distraction from other ANS Activities

• Had Planned to Have 4 Day Meeting at ANS Headquarters But Scrubbed Due to Expense Funding Issues

3

PROGRESS• Conference Call in Feb was Moderately

Successful.• We are Still Struggling With Use of the

“Capability Category” Approach as Applied to the Level 3 Standard

• Outlines Assigned Are Still About 75% Complete—But Most are Primitive and Need a Lot of Work. Little Progress Since Last Meeting

• Meeting Our Draft Writing Assignment Deadlines Needs Improvement!

• Struggling with Understanding Standard Format (Based on Combined Std)

SCHEDULE

• We Hope to Have a Reasonable Draft After a 4-Day Session at ANS Headquarters. This should be Scheduled for this Fall if we are to Meet a November target for providing a Clean Draft. Will Most Likely Not Take Place Until We Have Funding.

• We have been Told NRC has Approved Funding—No Official Word has Been Received as of this Meeting.

• At this Point the Schedule Will Have to Remain Uncertain

Capability Indices for Qualitative Risk Assessment (QLRA) Technical Elements

ANS Risk Informed Steering Committee June 17, 2009Doug HanceSenior Project ManagerEPRI Risk and Safety Management

pschroeder

Text Box

Attachment E


Introduction

• Review of Capability Categories – ASME PRA Standard

• Differences Between QLRA Capability Indices and Capability Categories

• Comparison Between 3 and 1 Capability Indices for QLRA


Review of ASME PRA Standard Capability Categories from RA-Sb-2005

1.3 PRA Capability Categories

• The Standard Is Intended for a Wide Range of Applications That Require A Corresponding Range of PRA Capabilities.

• Applications Vary With Respect to – Risk Metrics– Decision Criteria– Reliance on PRA Results– Degree of Resolution Required

• Three Capability Categories Defined - I, II, and III


Bases for PRA Capability Categories


Supporting Requirement Interpretation and Capability Categories - ASME RA-Sb-2005


Process - ASME PRA Standard RA-S-2002 Capability Categories – Fig. 3.1-1


ANS LPSD PRA Standard Draft 8C

1.3.4 Qualitative Capability Indices

• Standard Provides for Three Capability Indices for Shutdown QLRAs

• Three Different Descriptions for an SR Written to Address Three Different Capability Levels

• If an SR spans Multiple Capability Indices, it Applies Equally to Each Capability Index


ANS LPSD PRA Std. Draft 8C - TABLE 1.3.5.3-1 BASES FOR QLRA CAPABILITY INDICES

Attributes of QLRA I II III

1. Scope and level of detail: The degree to which the scope and level of detail of plant design, operation, and maintenance are modeled.

Resolution and specificity sufficient to identify the contributors to loss of key safety functions. Modeling is at the system and/or train level.

Resolution and specificity sufficient to identify the significant contributors to degradation and loss of key safety functions. Modeling of the front-line and associated support systems is at the train and super-component level. [Note (2)]

Resolution and specificity sufficient to determine the relative importance of the significant contributors to degradation and loss of key safety functions. Modeling of the front-line and associated support systems is at the super-component and component level. [Note (2)]

2. Plant Specificity Use of generic information, analyses or evaluations that account for unique design features of the plant.

Use of plant-specific information, analyses or evaluations for determining SSC, HRE and POS impact on key safety functions.

Use of plant-specific information, analyses or evaluations, including quantitative risk or reliability calculations, for determining SSC, HRE and POS impact on key safety functions.

3. Logical Structure [Note (1)]

Departures from the logical structure of the qualitative method will have moderate impact on the conclusions and risk insights as supported by good practices [Note (3)].

Departures from the logical structure of the qualitative method will have small impact on the conclusions and risk insights as supported by good practices [Note (3)].

Departures from logical structure of the qualitative method will have negligible impact on the conclusions and risk insights as supported by good practices [Note (3)].


ANS LPSD PRA Standard Draft 8C Section 7.3.1 - Scope and Purpose

• Recognizes That LPSD Quantitative PRAs are Used for a Variety of Applications

• Shutdown QLRAs are Limited to Shutdown Configuration Risk Management– Assess and Manage Risk of Individual Configurations

During Outages– Supports Evaluations Required by 10CFR50.65(a)(4)

• This is a Single Application


Draft 8C Section 7.3.2 - Determination and Description of Capability Indices

Capability Index I

• Basic Risk Assessment Of Configurations.

• Dependent on Other Inputs

• Determines Safety Function Viability and Identifies Important SSCs


Draft 8C – Section 7.3.2 (Continued)

Capability Index II:

• Graded Risk Assessment of Configurations

• Capability to Determine the Level Of Safety Function Availability and/or Degradation

• Capability to Identify SSCs Important to the Safety Functions

• Some Ability to Qualitatively Rank SSCs by Risk Impact, Based on End State Metrics.

• External Inputs Documented and Justified


ANS Draft 8C – Section 7.3.2 (Continued)

Capability Index III

• Risk Assessment of Configurations Correlated to Quantified Risk Values

• Capability to Determine the Level of Safety Function Availability or Degradation, and Correlate to Quantified Risk

• Capability to Identify SSCs Important to The Safety Functions

• Ability to Rank SSCs by Risk Impact.


Three QLRA Capability Indices - Advantages

• Clear Improvement Roadmap

• High Quality Peer Review Guidance– Addresses Scope, Level of Detail, and Logical

Structure– Proportional Review of Each Attribute

• Discrimination Between Basic, Graded, Quantitatively Correlated Models


One QLRA Capability Index - Advantages

• Simplicity and Proportionality– One Application; One Capability Index– Aligns with ASME PRA Standard

• Simplified Peer Review Guidance

• Clarity


Summary

• QLRA Capability Indices are Based on the ASME Standard Capabilities Categories Adapted to QLRA

• Differences Between Capability Categories and QLRA Capability Indices– One Application for QLRA (Shutdown CRM) vs.

Multiple Applications for Quantitative PRA– Definition Differences

• Recommendation: Three Capability Indices - Clear Improvement Path; High Quality Peer Review Guidance; Ability to Discriminate Between Basic, Graded, and Quantitatively Correlated Models


Together…Shaping the Future of Electricity

Shutdown Configuration Risk Management Overview

ANS Risk Informed Steering Committee June 17, 2009Doug Hance Senior Project ManagerRisk and Safety Management

pschroeder

Text Box

Attachment F


Shutdown Configuration Risk Management (CRM)

History• 1980s – 1990s:

– NRC and Industry Recognized the Need to Improve Shutdown Operations

• NUMARC 91-06 Issued December 1991

• 10CFR50.65(a)(4) – “Should” Changed to “Shall”– NUMARC 93-01 Rev. 3 Issued July 2000– Includes Shutdown– NUMARC 91-06 Content Included


Shutdown Configuration Risk Management (CRM)

History• EPRI Reports - 1989 to 2000

– TR 109014 and TR 113051 – 1989 to 1998– 1003113 – 1999 to 2000

• Goals – Determine Effectiveness of Industry Actions – Identify Industry Insights

• Long-Term Trending– Improvement Indicated Mid 1990s to 2000– Concerns with Precursors Remained


Shutdown CRM Results – EPRI Report 1003113


Shutdown CRM – NUMARC 91-06

NUMARC 91-06 Table of Contents

1.0 Introduction

2.0 Definitions

3.0 Outage Planning and Control

4.0 Shutdown Safety Issues

5.0 Assessment Process

6.0 References


NUMARC 91-06 Section 2.0 Selected Definitions

• CONTAINMENT CLOSURE: The action to secure primary (PWR) or secondary (BWR) containment and its associated structures, systems, and components as a FUNCTIONAL barrier to fission product release under existing plant conditions.

• CONTINGENCY PLAN: An approved plan of compensatory actions:– To maintain DEFENSE IN DEPTH by alternate means when pre-

outage planning reveals that specified systems, structures or components will be unavailable;

– To restore DEFENSE IN DEPTH when system AVAILABILITY drops below the planned DEFENSE IN DEPTH during the outage;

– To minimize the likelihood of a loss of KEY SAFETY FUNCTIONS during HIGHER RISK EVOLUTIONS.



• DECAY HEAT REMOVAL (DHR) CAPABILITY: The ability to maintain reactor coolant system (RCS) temperature and pressure, and spent fuel pool (SFP) temperature below specified limits following a shutdown.

• DEFENSE IN DEPTH: For the purpose of managing risk during shutdown, defense in depth is the concept of:– Providing systems, structures and components to

ensure backup of KEY SAFETY FUNCTIONS using redundant, alternate or diverse methods:

– Planning and scheduling outage activities in a manner that optimizes safety system AVAILABILITY;

– Providing administrative controls that support and/or supplement the above elements.



• HIGHER RISK EVOLUTIONS (HREs): Outage activities, plant configurations or conditions during shutdown where the plant is more susceptible to an event causing the loss of a key safety function.

• INVENTORY CONTROL: Measures established to ensure that irradiated fuel remains covered with coolant to maintain heat transfer and shielding requirements.

• KEY SAFETY FUNCTIONS (KSFs): During shutdown, they are decay heat removal, inventory control, power availability, reactivity control, and containment.


NUMARC 91-06 Section 3.0 Outage Planning and Control

• Sub-sections: – 3.1 Integrated Management – Schedule Planning,

Control, Outage Philosophy, Approval Authority– 3.2 Level of Activities – Resources, Potential Hazards– 3.3 Providing DID – Functionality, KSFs, HREs,

Optimize Availability, Procedures– 3.4 Contingency Planning – HREs, Alternate

Equipment, Monitoring, Controls– 3.5 Training – Operator, Temporary Personnel– 3.6 Outage Safety Review – Schedule Review,

Maintain DID, Contingency Plans, HREs

Subsections contain Guidelines


NUMARC 91-06 Section 4.0 Shutdown Safety Issues

• 4.0 Shutdown Safety Issues: – 4.1 DHR Capability (KSF) and 4.1.1 Loss of DHR

• Guidelines Include a Procedure to Address Loss of Normal DHR capability (shutdown) that: – Prioritizes Alternate Cooling Methods Available– Has a Sound Technical Basis Including Initial

Conditions (Decay Heat, Time to Boil, Time to Core Uncovery, RCS Inventory), RCS Configurations, Natural Circulation, • Provides Input for DHR DID

• Procedures Address Closing Containment Hatches or Penetrations Prior to Core Boiling Following Loss of DHR



• 4.1.2 Planning and Control (for Impact on DHR)– Evaluate DHR System Logic/Interlocks, Evaluate

Prior to Reduced Inventory or HREs, Activities Impacting core cooling Systems/Components Should be Scheduled for Low Decay Heat, Maximum Coolant Inventory, or Defueled Conditions

• 4.1.3 Loss of Spent Fuel Pool Cooling– Schedule Should Provide DID, Procedure

Established for Response to a Loss of SFP Cooling



– 4.2 Inventory Control (KSF)• 4.2.1 Reduced Inventory Operations (PWR) -

Defined as Occurring When the Vessel Water Level is Lower Than 3 feet Below the Flange– Mid-Loop – Special Case of Reduced Inventory

Operations – Level Below Top of the Hot Legs at Their Junction with the Vessel



• 4.2.1 (Continued) Reduced Inventory Operations Guidelines– Address Verification of Equipment

Requirements, Delaying Reduced Inventory Conditions When Decay Heat is High, Limitations During Mid-Loop Operation, Considerations for Reduced Inventory Conditions such as High Decay Heat, duration, Training, DID for DHR



• 4.2.2 Inadvertent Transfer of Coolant From RCS– Procedure to Address Loss of RCS Inventory

Including Potential Sources, Makeup, Coping with High Radiation Levels in Containment

– Address Plant Configurations Where a Single Active Failure or Personnel Error Can Result in Rapid Loss of Inventory,

– Managing Activities Impacting RCS Inventory, Including Procedures, Restoration Guidance, Alteration of RCS Flow Paths, Freeze Seals, and Control Rods and CRDs for BWRs.



• 4.2.3 Inventory Loss to Suppression Pool – Applies to BWR Shutdown Cooling Alignment– Maintain Automatic Isolation Function,

Administrative Controls for Valves Which Can Cause Rapid Inventory Loss

• 4.2.4 Inventory Loss Through Main Steam Lines (BWR)

• 4.2.5 Reactor Cavity Seal Failure– 4.3 Power Availability (KSF)– 4.4 Reactivity Control (KSF)– 4.5 Containment – Primary/Secondary (KSF)


NUMARC 91-06 Content – Major Sections Continued

• 5.0 Assessment ProcessShutdown

Safety Issues

Applicable?Non-Applicable

Issues(Document Basis)

ApplicableShutdown Safety

Issues

Evaluate CurrentPractices Against

Guidelines

Outage PlanningAnd

Control Elements

Meeting Guidelines?

DocumentBasis

IssuesNeedingActions

Develop and Implement Necessary Measures

Monitor Effectiveness

No

Yes

Yes

No


NUMARC 91-06 Implementation


Summary

• Background on Configuration Risk Management– NUMARC 91-06– Improved Trend Following Implementation

• Content of NUMARC 91-06– Definitions, Guidelines, Shutdown Safety Issues and

Process– Includes Management and Controls – Not Limited to

Technical Considerations

• Implementation of Shutdown CRM Programs– Follow and Expand NUMARC 91-06 Content


Together…Shaping the Future of Electricity

American Nuclear Society (ANS) Hyatt Regency … Nuclear Society (ANS) Risk-Informed Standards...

Documents

Transcript of American Nuclear Society (ANS) Hyatt Regency … Nuclear Society (ANS) Risk-Informed Standards...