Brunswick Nuclear Plant Storm Drain Stabilization Pond

Tritium Issues

BNP SDSPBNP SDSP

History

1977 - Stabilization Pond constructed from a spoil pond to provide Brunswick Nuclear Plant (BNP) with the capability to meet EPA effluent storm water release standards

1983 - Issuance of RETS. Stabilization Pond identified as a potential liquid effluent release point.

1992 - The licensee identified the Stabilization Pond as a previously unrecognized release point for tritium.

History

1997 - ANI Inspection Report In as much as the pond is unlined, the

likelihood of nuclide migration (particularly tritium) into the groundwater is relatively high.

History

2006 – BNP began to analyze water in manholes for tritium and gamma emitters

2007 - Tritium was discovered in manholes in vicinity of Storm Drain Stabilization Pond Values were 75,000 pCi/l to 150,000 pCi/l

2007 Standing/Flowing water containing tritium was found on the areas outside of the SDSP dike some of which was flowing toward intake canal. Values were 47,000 pCi/l to 880,000 pCi/l

.

History

As part of the expanded monitoring scope, resulting from the discovery of tritium in waters outside of the SDSP, more samples were taken and analyzed at various locations in and around the SDSP area.

Monitoring Wells installed at SDSP area.

MH < LLD

< LLD (Well)

MH < LLD

MH 76,210

MH166,800

336,800

47,450

804,100

WP-24<LLD

793,600 882,400

330,900

342,400

< LLD (well)

565,200 286,500391,200

281,600

604,500

36,050

197,400

93,410

180,400

607,200

1,511,000

BNP SDSPManhole and Surface Water Results June 2007

WP-48 (612)

WP-49 (409)WP-50 (413)

WP-51 (411)

WP-52 ND

WP-57 ND

WP-56 ND

WP-55 ND WP-54 NDWP-53 ND

WP-26 (281,600)

GUM LOG BRANCH

NANCY CREEK

WALDEN’S CREEK

WP-27 (36,050) RECOVERY POND

Expanded View of SDSP Area

ESS - 20 B & C

Well(s) Complete

ESS - 19 B & C

ESS - 22 B & C

ESS - 21 B & C

ESS - 24 A, B & C

Monitoring Wells

ESS - 23 C

ESS - 18 B & C

ESS – 17A, B & C

Stab Well

ESS - 25 B

ESS - 26 C

ESS – 27A & CESS - 28 C

ESS-NC-1

ESS-NC-2

ESS-NC-3

ESS-NC-4 ESS-NC-5 ESS-GLB-1

ESS - 25 C

ESS - 31 C

ESS - 30 C

Summary of Results

Highest activity taken in shallow wells was ~750,000 p/Ci/L.

Highest activity taken in intermediate wells was ~24,000 p/Ci/L.

Activity was not detected in deep wells.

Immediate/ Interim Corrective Actions

Reduced the primary input source of tritium to the SDSP Terminated unmonitored releases into the intake canal – instituted

compensatory measures Installed catch basins to route groundwater flow to the SDSP Installed hard pipe arrangement to release SDSP water to intake

canal versus open ditch Made voluntary notifications to government officials and the

community Installed new ground water monitoring wells around perimeter of

SDSP Performed a complete sample profile of the surface and

groundwater at locations around the perimeter of the stabilization pond to define the extent and magnitude of tritium activity

Planned Corrective Actions

Develop and implement a plant modification to stop major input source

Remediate Pond and Groundwater Conduct a full dose assessment of the impact to the

public Evaluate other potential areas/structures outside the

protected area that may exhibit the same characteristics or susceptibility to leakage (extent of condition/cause).

Install additional monitoring wells

Off-site Detections in Surface Water

Off-site Detections in Surface Water

Off-site Detections in Surface Water

Off-site Detections in Surface Water

Off-site Detections in Surface Water

Other Tritium Related Issues

SDSP tritium evaporation Accounted for approximately 74 curies in 2007 which yielded

approximately 2E-02 mrem inhalation dose to the nearest resident.

Model for transpiration still under development.

Liquid releases from marsh areas Marsh area releases are to Nancy's Creek Accounted for approximately 55 curies of tritium which yielded a

calculated dose of approximately 7.2E-04 mrem dose from fish consumption and 1.8E-04 mrem from invertebrates consumption (shrimp, crabs, etc.).

Methodology still under development for additional refinement relating to marsh and aquifer releases to surface water.

Planned Future Actions

Focused Groundwater Extraction with Containment and MNA to achieve the RAOs.

Establish a tritium fade and transport model to refine dose calculations.

Establish transpiration model for airborne dose modeling.

Questions