ML25224A203

Meeting Handouts - TSTF-608, MSL, Presubmittal Description

ML25224A203
Person / Time
Site:	Technical Specifications Task Force
Issue date:	08/07/2025
From:	Technical Specifications Task Force
To:	Office of Nuclear Reactor Regulation
References
Download: ML25224A203 (1)

Text

Technical Specifications Task Force A Joint Owners Group Activity TSTF OVERVIEW OF TSTF-608, "MAIN STEAM LINE AREA TEMPERATURE"

Technical Specifications Task Force A Joint Owners Group Activity TSTF Introduction

• TSTF-608 changes Technical Specification (TS) 3.3.6.1, "Primary Containment Isolation Instrumentation."

- Applicable to NUREG-1433 and NUREG-1434.

• Addresses Main Steam Line (MSL) area temperature monitoring.

• Proposes to replace automatic Group 1 isolation on MSL area temperature (i.e.,

Main Steam Line Isolation Valves (MSIVs) closure) with manual actions based on temperature limits.

• Change expands on license amendments approved for Plant Hatch and Limerick Generating Station.

- Those amendments moved a single MSL area temperature function to manual response.

- TSTF-608 is applicable to all TS 3.3.6.1 MSL Isolation Functions that:

• Measure the temperature around the MSLs as an indication of small MSL leakage, and

• Initiate an automatic Group 1 (or equivalent) primary containment isolation.

Technical Specifications Task Force A Joint Owners Group Activity TSTF Reason for the Proposed Traveler

• This traveler is proposed because:

- Automatic Group 1 isolation based on MSL area temperature could lead to unwarranted reactor trips.

- Temperature variations around the MSLs may occur due to non-leakage reasons (e.g., hot weather, ventilation issues, instrument calibration).

- No credit is taken for MSL area temperature monitoring and isolation in the accident analysis.

- Manual verification and shutdown provide a safer response should a small MSL leak occur.

Technical Specifications Task Force A Joint Owners Group Activity TSTF Overview of Proposed TS Changes

• Eliminates TS 3.3.6.1 Group 1 automatic isolation functions based on MSL area temperature.

- MSL areas vary by plant.

• Adds new specification TS 3.7.[9] for MSL Area Temperature monitoring.

- Includes all Functions removed from TS 3.3.6.1.

- Temperature is monitored every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> or in accordance with the Surveillance Frequency Control Program (SFCP).

- Temperature limits are unchanged unless justification is provided.

• If temperature exceeds limits:

- Action to verify no MSL leak immediately and once per 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> thereafter.

• If it cannot be confirmed that there is not an MSL leak, or if the periodic confirmation is not performed, a plant shutdown is required.

Technical Specifications Task Force A Joint Owners Group Activity TSTF Justification and Regulatory Evaluation

• Automatic isolation of MSLs based on MSL area temperature is not credited in the design basis accidents.

• Manual actions are sufficient to respond to small MSL leaks.

• The change reduces the risk of an unnecessary reactor trip.

• The change complies with regulatory requirements and maintains safety margins.

Technical Specifications Task Force A Joint Owners Group Activity TSTF Schedule

• The TSTF anticipates submitting TSTF-608 in the fourth quarter of 2025.

• Currently anticipate we will request a "normal" priority review.