ML25224A201
| ML25224A201 | |
| Person / Time | |
|---|---|
| Site: | Technical Specifications Task Force |
| Issue date: | 08/07/2025 |
| From: | Technical Specifications Task Force |
| To: | |
| References | |
| Download: ML25224A201 (1) | |
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Technical Specifications Task Force A Joint Owners Group Activity TSTF OVERVIEW OF TSTF-606, "REVISE THE ACTIONS ASSOCIATED WITH AN INOPERABLE ROD WORTH MINIMIZER (RWM)"
Technical Specifications Task Force A Joint Owners Group Activity TSTF Introduction
- The Rod Worth Minimizer (RWM) is part of the Control Rod Block Instrumentation in BWRs.
- It functions during low power operations (<10% RTP) to ensures compliance with the Banked Position Withdrawal Sequence (BPWS) to mitigate a Control Rod Drop Accident (CRDA).
- It acts as a backup to the operator and is not credited in accident analysis.
- An ACRS study determined the CRDA is a very low-probability event (1x10-12) without credit for the RWM.
- In 1986, the NRC approved removing CRDA evaluation from the GE standard reload evaluation.
The TS limit startups with an inoperable RWM to once per calendar year.
- This requirement was added to the STS in the early 1990's to ensure a reasonable degree of operability of the RWM, as at the time this backup system was frequently bypassed. The addition of this requirement predated the Maintenance Rule.
Technical Specifications Task Force A Joint Owners Group Activity TSTF Reason for the Proposed Traveler
- This traveler is being pursued because:
- If RWM issues are experienced by a licensee, the once-per-calendar-year constraint could prevent the startup of a reactor.
- The constraint is unnecessary because the function of the RWM can be adequately fulfilled by the use of a second licensed operator or other qualified member of the technical staff verifying the control rod movements are compliant with the BPWS.
- The safety benefit provided by the RWM is not commensurate with the potential operational impact.
- The traveler is similar to plant-specific amendments but takes a more comprehensive approach.
Technical Specifications Task Force A Joint Owners Group Activity TSTF Overview of Proposed TS Changes
- Revise the Actions of TS 3.3.2.1, "Control Rod Block Instrumentation."
- When the RWM is inoperable:
- Retain the requirement for independent verification that control rod movement is compliant with the BPWS.
- Eliminate the once-per-calendar-year restriction on reactor startup with inoperable RWM.
- Remove requirement to suspend control rod movement or verify 12 rods are withdrawn when RWM is inoperable.
- Combine Action C (RWM inoperable during startup) and Action D (RWM inoperable during shutdown) into a single Action for simplicity.
- The Action retains the current requirement to verify movement of control rods is in compliance with the BPWS by a second licensed operator or other qualified member of the technical staff.
Technical Specifications Task Force A Joint Owners Group Activity TSTF Justification and Regulatory Evaluation
- Independent verification of control rod movement ensures compliance with BPWS.
- The TS SR, Maintenance Rule, and Corrective Action Program ensure the RWM is maintained.
- The change complies with 10 CFR 50.36 and does not reduce safety margins, as the RWM is not credited in the safety analyses.
Technical Specifications Task Force A Joint Owners Group Activity TSTF Schedule
- Currently anticipate we will request a "normal" priority review.