L-MT-22-052, L-MT-22-052 Monticello Nuclear Generating Plant 10 CFR 50.55a Request No. Pr 08, Request for HPCI Pump Quarterly Alternative

L-MT-22-052 Monticello Nuclear Generating Plant 10 CFR 50.55a Request No. Pr 08, Request for HPCI Pump Quarterly Alternative

ML22350A726
Person / Time
Site:	Monticello
Issue date:	12/15/2022
From:	Jacobson R Xcel Energy
To:	Office of Nuclear Reactor Regulation
References
L-MT-22-052
Download: ML22350A726 (1)

Text

WEB-BASED PROPOSED ALTERNATIVE SUBMISSION Submission Date: December 15, 2022 Submitted By: Ronald Jacobson Document Sensitivity: Non-Sensitive Licensee: Xcel Energy Plant Unit(s) and Docket No(s): Monticello (05000263)

Licensee

Contact:

Ron Jacobson ronald.g.jacobson@xcelenergy.com 6123306542

1. Project

Title:

L-MT-22-052 Monticello Nuclear Generating Plant 10 CFR 50.55a Request No. PR 08, Request for HPCI Pump Quarterly Alternative

11. Proposed Alternative Number or Identifier:

PR 08

6. Request Type:

10 CFR 50.55a(z)(2)

7. Inservice Inspection (ISI) or Inservice Testing (IST)

Inservice Testing (IST)

10. Requested Completion Date:

January 14, 2023

12. Brief Description of Proposed Alternative Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter 'NSPM'), hereby requests NRC authorization of this 10 CFR 50.55a alternative for the Monticello Nuclear Generating Plant (MNGP).The proposed alternative is to defer the quarterly testing of components in the High Pressure Coolant Injection (HPCI) system until after the 2023 spring refueling outage when repairs to the 'G' SRV (Safety Relief Valve) will be completed.

13. Proposed Duration of Alternative (in terms of ISI/IST Program Interval with Start and End Dates):

The duration of this request will continue in the IST 6th Interval until MNGP's spring 2023 refueling outage, which is scheduled to start on April 15, 2023.

14. Applicable ASME Code Requirements ISTB-3400, Frequency of Inservice Tests. An inservice test shall be run on each pump as specified in Table ISTB-3400-1. That table specifies a Quarterly Group A Test for Pump Group A. ISTA-3170, Inservice Examination and Test Frequency Grace. Components whose test frequencies are based on elapsed time per table ISTA-3170-1, which states quarterly (every 3 months) and specifies 92 days between tests. ISTC-3510, Exercising Test Frequency. States in part: 'Active Category A, Category B, and Category C check valves shall be exercised nominally every 3 months...' Mandatory Appendix III-3721, HSSC [High Safety Significance] MOVs [Motor Operated Valves]. States in part: 'â HSSC MOVs that can be operated during plant operation shall be exercised quarterly â'

15. Applicable American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (BPV Code), or ASME Operation and Maintenanceâ-of Nuclear Power Plants (OM Code), Edition and Addenda American Society of Mechanical Engineers (ASME) Operation and Maintenance of Nuclear Power Plants (OM) Code, 2017 edition (no addenda).

16. Current ISI or IST Program Interval Number and Start/End Dates

IST 6th Interval started on October 1, 2022 and is scheduled to end on May 31, 2032.

17. Applicable ASME Code Components and/or System Description The following High Pressure Coolant Injection system components are affected:

Component Description Testing HPCI-18 HPCI Gland Seal Condenser/Lube Oil Exercise Open (CTO)

Cooler Cooling Water Return Check Valve HPCI-20 HPCI Gland Seal Exercise Close (CTC)

Condenser/Condensate Pump Discharge Check Valve Bi-Directional Open (BTO)

HPCI-32 HPCI Pump Suction from Condensate Exercise Open (CTO)

Storage Tank Check Valve HPCI-9 HPCI Turbine Exhaust Check Valve Exercise Open (CTO)

HPCI-10 HPCI Turbine Exhaust Check Valve Exercise Open (CTO)

MO-2036 HPCI Turbine Steam Supply Isolation Non-Timed Stroke Test (ET)

Valve P-209 HPCI pump Flow and Vibration

18. Reason for Request Safety relief valve RV-2-71G (G SRV) has elevated tailpipe temperature, indicative of pilot or second stage leakage that may result in a plant transient by spurious lift of the SRV which would likely require a rapid power reduction and may require a reactor scram. In addition, excessive leakage from the second stage may prevent the SRV from reseating following actuation which could challenge cooldown rate limits for the reactor vessel.

After a forced outage in January of 2022, the SRV tailpipe temperature of G SRV was approximately 10 degrees higher than prior to the outage. Over the last 9 months, temperature of the tailpipe has increased by approximately 8 degrees. Abnormal operating procedure entry criteria of 150 degrees F has been temporarily exceeded on three occasions: during adjustment of the reactor building closed cooling water (RBCCW) system temperature, coincident with

conducting flexible power operations, and coincident with the most recent performance of HPCI quarterly testing. Adjustments of RBCCW system temperature have been minimized and NSPM has curtailed conducting flexible power operations at MNGP until replacement of the 'G' SRV is completed in the spring 2023 refueling outage.

When the HPCI pump (P-209) is started, there is a sudden reduction in main steam pressure, particularly in the B main steam line which contains the 'G' SRV. Deferring the quarterly HPCI pump testing (and the accompanying exercising of HPCI components) will preclude introduction of this pressure transient and avoid further potential degradation of the SRV and the chances of a spurious lift.

19. Full Description of Proposed Alternative The proposed alternative, based on review of trending data, past test performance, and maintenance history, is to defer the quarterly ISTB-3400 Pump Group A tests of the HPCI pump, P-209. Performance of the quarterly pump test would be deferred in the fourth quarter of 2022 and the first quarter of 2023.

Deferral of the HPCI pump (P-209) testing also results in deferring quarterly check valve exercising in accordance with ISTC-3510 for HPCI-18, HPCI-20, HPCI-32, HPCI-9, and HPCI-10; and deferring quarterly MOV exercising in accordance with Mandatory Appendix III-3721 for MO-2036.

Normal testing of the HPCI system would resume following the G SRV (B Main Steam Safety Relief Valve) replacement during the spring 2023 refueling outage that is scheduled to start on April 15, 2023.

20. Description of Basis for Use A review of the completed maintenance and the IST results was performed for the HPCI pump P-209 and for the associated valves that would not be exercised if the pump is not run (HPCI-18, HPCI-20, HPCI-32, HPCI-9, HPCI-10, and MO-2036 valves) and concluded that these HPCI components would retain their operational readiness with no indication that mechanical or hydraulic degradation would challenge performance. The review included the history of the testing over the past 10 years.

Component Description History HPCI-18 Safety position is open. During the 2021 refueling outage a Opens to allow cooling water pressure test performed identified from the HPCI gland seal small chip on seating surface that was condenser and the lube oil corrected. There is no history of open cooler back to the suction of failures.

the booster pump. Its non-safety function is to prevent backflow from the gland seal condenser condensate pump during standby operations.

HPCI-20 Safety position is During the 2015 refueling outage the close: Closes to prevent valve was disassembled and backflow of water from the inspected. No issues were noted.

HPCI pump lube oil cooler to There is no history of open/close the gland seal condenser failures.

hotwell during standby mode and maintains the flow path of the gland seal and turbine lube oil cooler return flow during HPCI pump operation.

HPCI-32 Safety position is open/close. During the 2013 refueling outage the Allows flow to the HPCI valve was disassembled and pump from the condensate inspected. No issues were noted.

storage tank and isolation There is no history of open failures.

from back flow to the condensate storage tank.

HPCI-9 Safety position is open/close. During the 2019 and the 2021 Open to pass HPCI turbine refueling outages the valve was steam exhaust to the disassembled and inspected.

suppression pool during Identified slight pitting of seat at two operation and close to locations and scale that was cleaned provide a containment with scotch bright with confirmed 360 isolation when system is in deg of contact. There is no history of standby. open failures.

HPCI-10 Safety position is open/close. During the 2011 refueling outage Open to pass HPCI turbine following disassembly the seat ring steam exhaust to the was found to be in excellent condition suppression pool during and confirmed 360 deg of contact. It is operation and close to scheduled for maintenance in the provide a containment 2023 outage. There is no history of isolation when system is in open failures.

standby.

MO-2036 Safety position is open and is The valve and actuator for this valve a normally closed valve. were replaced in 2019. The diagnostic Allows steam flow to the testing indicates 21% margin for HPCI turbine. unseating thrust. The valve has adequate margin and no issues have been identified with the new valve/actuator.

P-209 Pumps water to reactor Pump trending of flow/differential vessel under loss of coolant pressure, oil and vibration are stable conditions that do not result and within acceptable range.

in rapid depressurization of the vessel.

Operation of the HPCI system for the most recent quarterly test had an adverse effect on the 'G' SRV tailpipe temperature, indicating operation of the HPCI system adversely affects SRV degradation. Degradation will increase the probability of a spurious lift of the SRV, which may result in a plant transient which would likely require a rapid power reduction and may require a reactor scram. Performance of quarterly HPCI pump testing presents a hardship as it increases the possibility of further degradation of the G SRV, and chances of a spurious lift, with no compensating increase in the level of quality or safety.

21. Include Any Additional Information Summary of Commitments: This submittal makes no new commitments and no revisions to existing commitments.

22. Precedents

None.

24. Attachments