RBG-48166, Supplement to Special Report for Tritium Discovered Onsite

Supplement to Special Report for Tritium Discovered Onsite

ML22132A288
Person / Time
Site:	River Bend
Issue date:	05/12/2022
From:	Karenina Scott Entergy Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RBG-48166
Download: ML22132A288 (2)

Text

) entergy RBG-48166 May 12, 2022 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Reference:

Supplement to Special Report for Tritium Discovered Onsite River Bend Station - Unit 1 NRC Docket Nos. 50-458 Renewed Facility Operating License No. NPF-47

1.

Special Report for Tritium Discovered Onsite (ML12025A155)

Kent Scott Site Vice President 225-381-4374 River Bend Station (RBS) submitted a "Special Report for Tritium Discovered Onsite" (Reference 1) dated January 19, 2012, in support of the Nuclear Energy Institute (NEI)

Groundwater Protection Initiative (NEl-07-07). The report stated that a positive groundwater sample result for tritium (48,244 pCi/L) exceeding the associated RBS Technical Requirements Manual reporting threshold and the NEI 07-07 guidance voluntary reporting threshold for tritium in groundwater (30,000 pCi/I) was confirmed from onsite monitoring well PZ-01 on December 20,2011.

In the attachment to the report titled "List of Regulatory Commitments," RBS committed to the following as a one-time action with no scheduled completion date: "RBS will supplement this letter upon identification and/or repair of the source of the leak." This letter fulfills that commitment.

Immediately after the confirmed detection of tritium in groundwater collected from monitoring well PZ-01, RBS began conducting groundwater and internal plant investigations to identify the source of the tritium. RBS developed a network of groundwater monitoring wells to trace the origin of the PZ-01 detection to beneath the power block foundation. Inspections of potential power block source terms and migration pathways were conducted and summarized using the Root Cause Evaluation process.

In 2014, RBS concluded that the source of tritium detected in groundwater collected from PZ-01 was a series of historical releases to the 67-ft Turbine Building and Heater Bay floors that migrated through a degraded North Heater Drain Pump seal and into underlying backfill material containing groundwater. The North Heater Drain Pump is hydraulically upgradient from the tritium plume containing monitoring well PZ-01, the "PZ-01 plume." RBS also identified a degraded South Heater Drain Pump seal, and subsequently expanded the groundwater monitoring network to confirm a second tritiated groundwater plume hydraulically downgradient Entergy Nuclear Operations, Inc., River Bend Station, 5485 U.S. Highway 61, St. Francisville, LA 70775

RBG-48166 Page 2 of 2 from the South Heater Drain Pump beneath the Independent Spent Fuel Storage Installation (ISFSI), the "ISFSI plume."

RBS completed repairs to degraded North Heater Drain Pump and South Heater Drain Pump seals in March 2015. An epoxy coating was applied to the Turbine Building floor in June 2016.

The primary groundwater remediation strategy at RBS is Monitored Natural Attenuation (MNA),

which allows the natural processes of dilution and decay to decrease tritium concentrations. A pump and discharge groundwater remediation system was operated within the PZ-01 plume near the power block from 2014 to 2015. However, effects on groundwater tritium concentrations were temporary.

Active mitigation measures completed in 2016 created a subsurface environment for MNA in which tritium concentrations in monitoring wells have shown statistically significant decreasing trends at 90% confidence. The trends indicate the source of tritium in groundwater was properly identified and mitigated, and that additional source material is no longer being added to the groundwater system.

This letter contains no new regulatory commitments.

Should you have any questions, please contact Mr. Tim Schenk, Regulatory Assurance Manager, at 225-381-4177.

Respectfully, KCS/twf cc:

r!J..ll!N:,iuarl'l IV Regional Administrator - Region IV NRG Senior Resident Inspector - River Bend Station Entergy Nuclear Operations, Inc., River Bend Station, 5485 U.S. Highway 61, St. Francisville, LA 70775