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Category:Letter
MONTHYEARML24255A8312024-09-23023 September 2024 Project Manager Assignment ML24261B9782024-09-19019 September 2024 Notification of an NRC Fire Protection Team Inspection NRC Inspection Report 05000413-2024010, 05000414-2024010 and Request for Information IR 05000413/20243012024-09-16016 September 2024 Operator Licensing Examination Approval 05000413/2024301 and 05000414/2024301 IR 05000414/20240912024-09-0505 September 2024 Final Significance Determination of a White Finding and Nov and Assessment Followup Letter-NRC Inspection Report 05000414-2024091 IR 05000413/20240052024-08-26026 August 2024 Updated Inspection Plan for Catawba Nuclear Station (Report 05000413/2024005 & 05000414/2024005) ML24235A1542024-08-22022 August 2024 Notification of Target Set Inspection and Request for Information (NRC Inspection Report 05000413-2024402 and 05000414-2024402) IR 05000413/20240022024-08-0808 August 2024 Integrated Inspection Report 05000413-2024002 and 05000414-2024002 and Apparent Violation IR 05000413/20244032024-08-0101 August 2024 Information Request for the Cybersecurity Baseline Inspection, Notification to Perform Inspection 05000413/2024403; 05000414/2024403 ML24183A0972024-07-12012 July 2024 ISFSI; Catawba 1, 2 & ISFSI; McGuire 1, 2 & ISFSI; Oconee 1, 2, 3 & ISFSI; Shearon Harris 1; H. 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July 22, 2020 Mr. Robert T. Simril Site Vice President Catawba Nuclear Station Duke Energy Carolinas, LLC 4800 Concord Road York, SC 29745
SUBJECT:
CATAWBA NUCLEAR STATION, UNITS 1 AND 2 - U.S. NUCLEAR REGULATORY COMMISSION STAFF REVIEW OF BORIC ACID PRECIPITATION CONCERNING GENERIC LETTER 2004-02
Dear Mr. Simril:
In September 2004, the U. S. Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors [PWR] (Agencywide Documents Access and Management System (ADAMS) Accession No. ML042360586), to holders of operating licenses for PWRs. In GL 2004-02, the NRC staff requested that licensees perform an evaluation of their emergency core cooling system (ECCS) and containment spray system (CSS) recirculation functions, considering the potential for debris-laden coolant to be circulated by the ECCS and the CSS after a loss-of-coolant accident (LOCA) or high-energy line break inside containment, and, if appropriate, take additional action to ensure system function. GL 2004-02 required, per Title 10 of the Code of Federal Regulations (10 CFR) Section 50.54(f), that licensees provide the NRC a written response describing the results of their evaluation and any modifications made, or planned, to ensure ECCS and CSS system function during recirculation following a design-basis event, or any alternate action proposed and the basis for its acceptability.
In letter dated December 31, 2013 (ADAMS Accession No. ML13331A673), the NRC documented that Catawba Nuclear Station, Units 1 and 2 (Catawba) had provided all information required to close GL 2004-02. Documentation for closure of the in-vessel portion of GL 2004-02 was performed by demonstrating that Catawba met the requirements of topical report (TR) WCAP-16793-NP-A, Revision 2, and the associated NRC staff safety evaluation (SE) (ADAMS Accession No. ML13239A114). In its SE, the NRC staff concluded that plants with relatively low fiber amounts reaching the core could use the TR methodology to show that core cooling would not be adversely affected by debris. However, the SE stated that the potential for debris to change flow patterns or inhibit the mixing of boric acid in the core that might result in earlier boric acid precipitation (BAP) had not been evaluated. This left the question of the effects of debris on the plant licensing basis for BAP open.
The Pressurized Water Reactors Owners Group continued to evaluate the effects of larger amounts of debris on long-term core cooling (LTCC). This work is documented in TR WCAP-17788, Revision 1 (ADAMS Package Accession No. ML20010F181). The NRC staff performed a thorough review of this TR but was unable to conclude that the methodology used for evaluating reactor core debris limits was acceptable for licensing basis calculations.
R. Simril However, the NRC staff found that the TR methodology provided meaningful safety and regulatory insights regarding the treatment of BAP. The staffs technical review of the TR methodology is documented in its technical evaluation report (TER) (ADAMS Accession No. ML19178A252). WCAP-17788, Rev. 1, evaluated the potential for debris to affect current BAP analyses and found that BAP timing would not be adversely affected. The NRC performed sensitivity studies during its review of WCAP-17788, Rev 1. These analyses explicitly modeled the physical phenomena that affect the potential for BAP and were conducted for reactor designs considered to be the most limiting with respect to BAP. The analyses found that debris collecting at the core inlet would not adversely affect BAP timing under conditions that conservatively modeled the effects of debris. The NRC staff determined that licensees that demonstrate that their plants fall within specific bounds can maintain their current licensing basis for BAP (Refer to Staff Guidance ADAMS Accession No. ML19228A011), even with debris amounts greater than those approved in WCAP-16793-NP-A, Rev. 2.
In its response to GL 2004-02, Catawba demonstrated that it has a very small amount of fiber that may arrive at the core inlet. The NRC staff has determined that this amount of debris will not adversely affect BAP timing and Catawba can maintain its current licensing basis for BAP.
The NRC staff has no further questions related to potential effects of post-accident debris on the reactor vessel and therefore, the conclusion in the December 31, 2013, letter that Catawba had adequately responded to GL 2004-02, remains unchanged for the items addressed.
If you have any questions, please contact me at 301-415-1438 or via e-mail at Karen.Cotton@nrc.gov.
Sincerely,
/RA/
Karen Cotton-Gross, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-413 and 50-414 cc: Listserv
ML20161A106
- Concurred by email OFFICE NRR/DORL/LPLII-1/PM NRR/DORL/LPLII-1/LA* NRR/DSS/STSB/BC*
NAME KCotton KGoldstein VCusumano DATE 07/22/20 07/21/2020 05/19/2020 OFFICE NRR/DORL/LPLII-1/BC* NRR/DORL/LPLII-1/PM NAME MMarkley (SWilliams for) KCotton DATE 07/22/2020 07/22/2020