ML25007A235
| ML25007A235 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 01/07/2025 |
| From: | Kivi J Northern States Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML25007A235 (1) | |
Text
WEB-BASED PROPOSED ALTERNATIVE SUBMISSION 10 CFR 50.55a(z)(2)
Submission Date: 01/07/2025 Submitted By: Jeffrey Kivi Submission Availability: Non-Publicly Available Licensee: Northern States Power Company Plant Unit(s) and Docket No(s): Prairie Island 2 ( 05000306 )
Licensee
Contact:
Jeffrey Kivi (612) 330-5788 jeffrey.l.kivi@xcelenergy.com Project
Title:
L-PI-25-001 Prairie Island Nuclear Generating Plant (PINGP) Unit 2 Inservice Testing Proposed Alternative RR-10 Request Type:
Inservice Inspection (ISI) or Inservice Testing (IST)
Inservice Testing (IST)
Requested Completion Date:
February 07, 2025 Proposed Alternative Number or Identifier:
IST 5th Interval RR-10 Brief Description of Proposed Alternative
Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter NSPM) is requesting relief from the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code) Inservice Testing of Valves in Light-Water Reactor Nuclear Power Plants (Subsection ISTC) code required inservice testing for Volume Control system (VC) Category B control valve CV-31279, Unit 2 Letdown Line Isolation Train B Control Valve, where testing represents a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Proposed Duration of Alternative (in terms of ISI/IST Program Interval with Start and End Dates):
This alternative will continue from approval until startup from the next Unit 2 refueling outage, currently scheduled for 10/31/2025 or the end of the 5th interval, whichever comes first.
Applicable ASME Code Requirements ISTC-3310 Effects of Valve Repair, Replacement, or Maintenance on Reference Values. When a valve or its control system has been replaced, repaired, or has undergone maintenance that could affect valve performance parameters, a new reference value shall be determined or the previous value reconfirmed by an inservice test run before the time it is returned to service or immediately if not removed from service. This test is to demonstrate that performance parameters that could be affected by the replacement, repair, or maintenance are within acceptable limits. Deviations between the previous and new reference values shall be identified and analyzed. Verification that the new values represent acceptable operation shall be documented in the record of tests (see ISTC-9120). Safety and relief valves and nonreclosing pressure relief devices shall be tested as required by the replacement, repair, and maintenance requirements of Mandatory Appendix I.
Applicable American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code),
or ASME Operation and Maintenanceof Nuclear Power Plants (OM Code), Edition and Addenda ASME OM Code 2004, 2006 Addenda Current ISI or IST Program Interval Number and Start/End Dates 5th IST Interval; started 12/21/2014 and scheduled to end 12/20/2025 using the 12-month extension allowed by ISTA-3120(d).
Applicable ASME Code Components and/or System Description
CV-31279, Unit 2 Letdown Line Isolation Train B Control Valve. CV-31279 is a 2-inch air-operated globe valve. This normally open/failed close Air-Operated Valve (AOV) is the second series valve from the Reactor Coolant System (RCS) Loop B cold leg and is open during normal operations to place the normal letdown path in service. Letdown is not required for safe shutdown or accident mitigation. The valve closes automatically on low pressurizer level, loss of power, or loss of air.
The letdown line is provided with two fail-closed, air-operated valves near the reactor coolant loop. The RCS to the Chemical and Volume Control System boundary occurs at the second isolation valve. In the event of low pressurizer level, these valves are automatically closed.
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Reason for Request===
On 08/06/2024 CV-31279, which is normally open during operation at power and typically is not operated for routine plant operation, was closed in support of maintenance on an unrelated system. At that time, dual light indication was observed when the valve was expected to indicate closed. After evaluating the effect of having a degraded, potentially non-functional component and based on a desire to restore letdown to normal operation, the valve was returned to its normal open/auto-close condition prior to determining the cause of the dual light indication. On 09/11/2024, during investigation of the issue, plant personnel identified that the valve stem rod that functions to actuate the limit switch was misaligned. The valve was observed to travel to the full open and full closed positions in approximately the normal amount of stroke time. The valve stem rod was manually adjusted at that time to improve the remote indication, but not corrected in a manner that ensured it would remain in place.
On 10/11/2024, NRC staff informed plant personnel that the adjustment of the valve stem rod should have been classified as maintenance that could have affected valve performance parameters per ISTC-3310; therefore, testing CV-31279 was required. Because PINGP became aware of the need for testing while CV-31279 was in service, per ISTC-3310 testing is required immediately.
To correct the issue with the valve stem rod requires disassembly of the actuator which would be a hardship at power due to radiological conditions. In order to perform the inservice test of CV-31279 during plant operation, letdown would need to be isolated which would cause flow perturbations, pressurizer level swings, and thermal cycles on the primary piping nozzles. The proposed alternative to delay testing will not reduce safety as the condition is known to be related to the remote position indication, and CV-31279 has been verified to operate properly to its closed position. The remote position indication for CV-31279 does not affect the valves ability to perform its function.
Full Description of Proposed Alternative Rather than perform immediate testing, NSPM proposes to correct the valve position indication issue and perform the required testing during the next scheduled Unit 2 refueling outage because performing the inservice test run on CV-31279 immediately would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Description of Basis for Use
Compliance with the specified requirements of this section for the affected component would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
In order to perform the inservice test of CV-31279 during plant operation, letdown would need to be isolated which would cause flow perturbations, pressurizer level swings, and thermal cycles on the primary piping nozzles.
Additionally, to correct the issue with the valve stem rod requires disassembly of the actuator which would be a hardship at power due to radiological conditions. The proposed alternative to delay testing will not reduce safety as the condition is known to be related to the remote position indication, and CV-31279 has been verified to operate properly to its closed position. The remote position indication for CV-31279 does not affect the valves ability to perform its function.
Include Any Additional Information This submittal makes no new commitments and no revisions to existing commitments.
Precedents None.
References
- 1.
American Society of Mechanical Engineers Code for Operation and Maintenance of Nuclear Power Plants 2004 Edition, 2006 Addenda
- 2.
Prairie Island Nuclear Generating Plant ASME Inservice Testing Program Attachments