History l 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 l 1983 - Issuance of RETS. Stabilization Pond identified as a potential liquid effluent release point. l 1992 - The licensee identified the Stabilization Pond as a previously unrecognized release point for tritium.
History l 1997 - ANI Inspection Report w In as much as the pond is unlined, the likelihood of nuclide migration (particularly tritium) into the groundwater is relatively high.
History l 2006 – BNP began to analyze water in manholes for tritium and gamma emitters l 2007 - Tritium was discovered in manholes in vicinity of Storm Drain Stabilization Pond w Values were 75,000 pCi/l to 150,000 pCi/l 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. w Values were 47,000 pCi/l to 880,000 pCi/l.
History l 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. l Monitoring Wells installed at SDSP area.
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 ND WP-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 & C ESS - 28 C ESS-NC-1 ESS-NC-2 ESS-NC-3 ESS-NC-4 ESS-NC-5ESS-GLB-1 ESS - 25 C ESS - 31 C ESS - 30 C
Summary of Results l Highest activity taken in shallow wells was ~750,000 p/Ci/L. l Highest activity taken in intermediate wells was ~24,000 p/Ci/L. l Activity was not detected in deep wells.
Immediate/ Interim Corrective Actions l Reduced the primary input source of tritium to the SDSP l Terminated unmonitored releases into the intake canal – instituted compensatory measures w Installed catch basins to route groundwater flow to the SDSP w Installed hard pipe arrangement to release SDSP water to intake canal versus open ditch l Made voluntary notifications to government officials and the community l Installed new ground water monitoring wells around perimeter of SDSP l 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 l Develop and implement a plant modification to stop major input source l Remediate Pond and Groundwater l Conduct a full dose assessment of the impact to the public l Evaluate other potential areas/structures outside the protected area that may exhibit the same characteristics or susceptibility to leakage (extent of condition/cause). l Install additional monitoring wells
Other Tritium Related Issues l SDSP tritium evaporation w Accounted for approximately 74 curies in 2007 which yielded approximately 2E-02 mrem inhalation dose to the nearest resident. w Model for transpiration still under development. l Liquid releases from marsh areas w Marsh area releases are to Nancy's Creek w 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.). w Methodology still under development for additional refinement relating to marsh and aquifer releases to surface water.
Planned Future Actions l Focused Groundwater Extraction with Containment and MNA to achieve the RAOs. l Establish a tritium fade and transport model to refine dose calculations. l Establish transpiration model for airborne dose modeling.