ML24159A275
ML24159A275 | |
Person / Time | |
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Site: | Cook |
Issue date: | 05/30/2024 |
From: | Indiana Michigan Power Co |
To: | Office of Nuclear Reactor Regulation |
Shared Package | |
ML24159A261 | List:
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References | |
AEP-NRC-2024-20 | |
Download: ML24159A275 (1) | |
Text
Donald C. Cook Nuclear Plant Report of Changes, Tests, Experiments Pursuant to 10 CFR 50.59(d)(2)
As required by 10 CFR 50.59(d)(2), the following report contains brief descriptions of changes made to the facility and/or associated documentation, and summaries of the associated 50.59 evaluations.
SS-SE-2023 -0013- 00
D.C. Cook Unit 1 Extension of Quarterly Main Turbine Valve Testing
ACTIVITY DESCRIPTION:
The Change is an extension of the Unit 1 Main Turbine valve testing interval from 3 months to 8 months. Typically, the frequency of performing a test would be considered maintenance and would not be subject to a 50.59 Review. However, the frequency of Main Turbine valve testing is specifically described in Updated Final Safety Analysis Report (UFSAR), Section 1.4.7, and is an input to Main Turbine failure probability and compliance with Plant Specific Design Criterion 40 for main turbine missile protection. Thus, a change to the Main Turbine valve testing frequency will impact the facility as described in the UFSAR and is subject to a 50.59 Review.
Summary of the Evaluation:
The main turbine failure probability is 2.22E -5 per reactor year for valve testing performed on an eight-month frequency. The main turbine missile generation acceptance criteria for continuous operation is < 1 E-5 per reactor year for an "unfavorably oriented turbine" such as D.C. Cook Unit 1. The proposed change in main turbine valve testing frequency results in a small increase in probability of main turbine missile generation due to a destructive overspeed event.
Regulatory guidance states that if the probability of missile generation is between 1E-5 and 1E-4, then main turbine operation may continue until the next scheduled outage. The performance of valve testing will restore missile probability to within 1E -5 per reactor year.
The proposed change has been quantitatively determined to meet existing regulatory guidance applicable to D.C. Cook to allow resolution before the next scheduled outage. That guidance constitutes industry precedent on actions applicable if the continuous operation criterion is not met. This issue will be resolved when valve testing is performed within the eight-month window specified. Therefore, the proposed activity does not result in more than a minimal increase in the likelihood of occurrence of a malfunction of an Safety, System, Component (SSC) important to safety previously evaluated in the UFSAR, and all 50.59 evaluation questions were answered no.
Donald C. Cook Nuclear Plant Report of Changes, Tests, Experiments Pursuant to 10 CFR 50.59(d)(2)
SS-SE-2021- 0022- 00
D.C. Cook Unit 2 Ice Basket Replenishment Deferral
When preparing for ice basket replenishment scheduled to occur during the fall 2022 Unit 2 refueling outage, it was determined that a portion of the ice baskets would not be replenished.
The unit would then operate through the ensuing cycle with some ice basket weights less than the safety analysis mean. 50.59 Evaluation SS-SE-2021- 0022- 00 was credited by the 50.59 applicability determination associated with this change package.
Activity
Description:
To reduce the risk to plant staff and plant operation posed by the then-current COVID-19 Pandemic, a plan was implemented for the ice condenser to be returned to service after the U2 Spring-2021 refueling outage without undergoing typical ice basket replenishment. The Unit was then operated through the ensuing operating cycle with ice bed basket weights less than the safety analysis mean value.
Summary of the Evaluation:
Each of the 8 evaluation questions were answered No. Although ice bed replenishment was deferred for an operating cycle, it was shown that operation with some ice basket weights below the safety analysis mean value (but above a projected minimum) would continue to support all applicable design basis functional requirements. Specifically, it was shown using methods of evaluation consistent with those within the UFSAR (where applicable) that the ice bed would continue to ensure sufficient ice mass, heat transfer area, flow passages, and ice distribution would be provided in the ice condenser so that the magnitude of a pressure and temperature transients resulting from accidents described in the UFSAR would not exceed the containment design pressure or temperature.