RS-15-047, Supplemental Information in Support of Request for a License Amendment, Technical Specification 3.7.9, Ultimate Heat Sink, Dated August 19, 2014

Supplemental Information in Support of Request for a License Amendment, Technical Specification 3.7.9, Ultimate Heat Sink, Dated August 19, 2014

ML15020A246
Person / Time
Site:	Braidwood
Issue date:	01/20/2015
From:	Gullott D Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-15-047
Download: ML15020A246 (3)

Text

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...... 4300 Winfield Road Warrenville. IL 60555 AN-Pr- Exelon Generation 630 657 2000 Office 10 CFR 50.90 RS-15-047 January 20, 2015 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456, STN 50-457

Subject:

Supplemental Information in Support of Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical specification 3.7.9, "Ultimate Heat Sink"

Reference:

Letter from David M. Gullott (Exelon Generation Company, LLC) to U. S. Nuclear Regulatory Commission "Request for a License Amendment to Braidwood Station, Units 1 and 2, Technical Specification 3.7.9, 'Ultimate Heat Sink'," dated August 19, 2014 By letter dated August 19, 2014 (Reference), Exelon Generation Company, LLC (EGC) submitted a request pursuant to 10 CFR 50.90, "Application for amendment of license, construction permit, or early site permit," for Braidwood Station requesting U.S. Nuclear Regulatory Commission approval to revise Technical Specification (TS) Surveillance Requirement (SR) 3.7.9.2. Specifically, TS SR 3.7.9.2 currently states: "Verify average water temperature of UHS [Ultimate Heat Sink] is 5 100°F." The proposed license amendment (Reference) sought to increase the TS SR 3.7.9.2 allowable temperature to 5 102°F. EGC requested approval of the Reference amendment by August 19, 2015.

In October of 2014, a hydrographic survey was conducted of the UHS. The purpose of the survey was to ensure the average elevation of the bottom of the UHS is at or below 584 feet MSL to verify compliance with TS SR 3.7.9.3. Before beginning the survey, Braidwood Station engineering personnel requested that additional information be collected during the surveillance to validate the height of the UHS as described in UFSAR section 2.4.1.1, 2.4.11.6 and Figures 2.4-47 and 2.4-48. The essential service cooling pond [ESCP] is located in the northwestern corner of the Braidwood Station lake main pond in an area excavated to an elevation of 584 feet. The design volume of the ESCP is based on a depth of 6.0 feet with the top berm of the UHS excavation at 590.0 feet (see Figure 2.4-47).

The October 2014 hydrographic survey found the bottom of the UHS at an average elevation of 583.7 feet, thus meeting TS SR 3.7.9.3. However, the survey results also showed that the as-

U.S. Nuclear Regulatory Commission January 20, 2015 Page 2 found elevation of the top berm on the East side of the UHS was 589.4 feet, 0.6 feet less than the 590.0 feet described in UFSAR section 2.4.1.1 and 2.4.11.6. The as-found condition of the UHS reduces the water available for heat removal during a design basis event. The volume enclosed by this contour line is approximately 528 acre-feet, which is approximately 5% less than the design volume of 555.8 acre-feet. Adequate water volume within the UHS is a critical parameter within the UHS performance analysis that demonstrates that the UHS can provide a minimum of 30 day supply of water while not exceeding the TS SR 3.7.9.2 temperature limit of 100°F during and following a design basis accident (DBA). The lower than expected survey results were entered into the Corrective Action Program and the difference between the as-found volume and the design volume was evaluated in an Operability Evaluation.

The Operability Evaluation determined that the post-DBA UHS temperature would remain less than the 100°F temperature limit prescribed in TS SR 3.7.9.2 with certain compensatory measures in place. The compensatory measures include administratively lowering the allowable UHS temperature to 97°F or limiting the number of Essential Service Water (SX) pumps in operation to three for the UHS design basis event. Since lowering the allowable UHS temperature is not a long term solution to addressing the recently observed (July 2012) meteorological conditions that have challenged the UHS temperature limit and is inconsistent with the Reference request, Braidwood Station intends to return the UHS configuration back to the design configuration by restoring the elevation of the UHS East side top berm to a minimum elevation of 590 feet. One of the compensatory measures currently implemented at Braidwood Station will remain implemented until the top UHS elevation is restored to the design configuration.

The UHS configuration restoration plan consists of installing a row of sheet pile wall just east of the UHS (i.e., where the elevation of the top berm was found to be less than 590.0 feet) to a top height of 591.0 feet. This will ensure the design basis of 590.0 feet is met and that adequate UHS volume exists to ensure the UHS can provide a minimum of 30 day supply of water while not exceeding the existing TS SR 3.7.9.2 (i.e., 100°F) and the proposed revised TS SR 3.7.9.2 (i.e., 102°F) contained in Reference. The projected completion date is June 2015.

This supplement is being provided to describe the issue recently discovered and identify Braidwood Station's plan for restoration of the UHS. While the potential exists for the recently discovered UHS height to be less than that evaluated in the Reference submittal, Braidwood Station's plan for UHS restoration by June 2015 ensures that the information and supporting evaluations included in the Reference submittal remain accurate for the planned UHS restoration. Upon completion of the restoration of the UHS configuration, EGC will notify the NRC by submitting a follow-up letter. Additionally, EGC is currently evaluating submitting a License Amendment Request for inclusion of the top height of the UHS berm (i.e., 590 feet) within the existing TS 3.7.9 SRs.

U.S. Nuclear Regulatory Commission January 20, 2015 Page 3 If you have any questions or require additional information, please contact Jessica Krejcie at 630-657-2816.

Respectfully, David M . Gullott Manager Licensing Exelon Generation Company, LLC cc: Regional Administrator-NRC Region III NRC Senior Resident Inspector- Braidwood Station NRC Project Manager, NRR Braidwood Station