05000498/LER-2023-001-01, Supplement to Pressurizer Power Operated Valve Failed to Open
| ML23207A220 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 07/26/2023 |
| From: | Harshaw K South Texas |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NOC-AE-23003977, 35493028, G26 LER 2023-001-01 | |
| Download: ML23207A220 (1) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 4982023001R01 - NRC Website | |
text
July 26, 2023 NOC-AE-23003977 10 CFR 50.73 STI: 35493028 File No. G26 Attention: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 South Texas Project Unit 1 Docket No. STN 50-498 Licensee Event Report 2023-001-01 Supplement to Unit 1 Pressurizer Power Operated Valve Failed to Open
Reference:
Letter; K. Harshaw (STP) to Document Control Desk (NRC); Licensee Event Report 2023-001-00 Unit 1 Pressurizer Power Operated Valve Failed to Open; June 12, 2023; (NOC-AE-23003967) (ML23163A248).
On June 12, 2023, STP Nuclear Operating Company (STPNOC) submitted the referenced Licensee Event Report. This letter is a supplement to the report to provide the updated results of the causal evaluation. The updated information is denoted by revision bars located in the right-hand margin. The report is submitted in accordance with 10 CFR 50.73.
The event did not have an adverse effect on the health and safety of the public.
There are no commitments in this submittal.
If there are any questions on this submittal, please contact Zachary Dibbern at 361-972-4336 or me at 361-972-4778.
Kimberly A. Harshaw Executive Vice President and Chief Nuclear Officer
Attachment:
LER 2023-001-01, Unit 1 Pressurizer Power Operated Valve Failed to Open cc:
Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 1600 E. Lamar Boulevard Arlington, TX 76011-4511
NOC-AE-23003977 Attachment Attachment LER 2023-001-01 Unit 1 Pressurizer Power Operated Valve Failed to Open
Abstract
07 26 D
On March 18, 2023, at 0933, during the shutdown of Unit 1 reactor for 1RE24, while in Mode 4 and performing surveillance procedure steps for Pressurizer Power Operated Relief Valve (PORV) PCV-0656A, the valve failed to open. The surveillance was successfully reperformed later that shift and the valve was declared operable. The capability of the PORV to meet its design function for manual control of RCS pressure if it had been called upon to perform its safety functions from 11/3/2021 to 3/18/2023, was not assured. Therefore, PORV 0656A was considered to have been inoperable during this time. On 1/4/2023, from 0757 until 1431, the PORVs could not have fulfilled their safety function for manual control of RCS pressure under postulated design basis conditions, because the second PORV 0655A was unavailable due to scheduled maintenance. The event was determined to be reportable per 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications and per 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented fulfillment of a safety function. The cause of the event was determined to be inadequate guidance in the PORV maintenance procedure and inadequate implementation of a design change package. Corrective actions include revising and updating procedures and documentation.
Zachary E. Dibbern, Licensing Engineer (361) 972-4336
Summary of the Event Timeline (Note: All times Are Central Standard Time) 11/03/21 (1305) - Closed PZR PORV PCV-0656A Block Valve to determine if Pressurizer Safety Relief Valve HI temperature alarm was due to PZR PORV PCV-0656A seat leakage. Entered TS 3.4.9.3.
11/03/21 (1519) - Unit 1 entered Mode 3. TS 3.0.4.a was invoked for entering Mode 3 with PCV-0656A inoperable due to excessive seat leakage. Exited TS 3.4.9.3 and entered TS 3.4.4 Action (a) for PCV-0656A inoperable because of excessive seat leakage. The associated block valve remains closed with power on.
01/04/23 (0750) - Battery Bank E1A11 (power supply for PCV-0655A) declared inoperable and non-functional for planned maintenance.
01/04/23 (0950) - The Technical Specification 3.8.2.1.a Limiting Condition of Operation Action (a) and Technical Specification 3.8.3.1.h Action (e) for planned maintenance on Battery Bank E1A11 exceeded front stop completion time requiring entry into risk managed Technical Specifications.
01/04/23 (2345) - Declared ESF Battery E1A11 functional after being placed on 'float charge' with battery recharged.
03/17/23 (2251) - Unit 1 entered Mode 3 for 1RE24.
03/18/23 (0915) - Unit 1 entered Mode 4 for 1RE24. Entered Technical Specification 3.4.9.3 Action (c) for PCV-0656A inoperable. Technical Specification 3.4.4 for PCV-0656A is no longer applicable.
03/18/23 (0928) - Opened block valve for PCV-0656A. When opening block valve, PCV-0656A momentarily indicated an intermediate position.
03/18/23 (0933) - PCV-0656A failed to open during surveillance testing. Control board indication for Pressurizer PORV open command signal received at 0933:13.
03/18/23 (0937) - Control board indication for Pressurizer PORV open command signal cleared at 0937:10. Block Valve for PCV-0656A closed at 0937:22.
03/18/23 (0951) - PCV-0656A failed to stroke open during surveillance testing. The time of inoperability is tied to Mode 4 entry at 0915 on 03/18/2023. Remained in Technical Specification 3.4.9.3 Action (c).
03/18/23 (1218) - Opened block valve for PORV PCV-0656A to warm up lines for shutdown activities.
03/18/23 (1302) - Unit 1 entered Mode 5; entered Technical Specification 3.4.9.3 Action (d) for PCV-0656A inoperable and exited Technical Specification 3.4.9.3 Action (c).
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- 3. LER NUMBER YEAR SEQUENTIAL NUMBER REV NO.
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V. Corrective Actions
The corrective action to prevent reoccurrence is to revise the procedure for pressurizer PORV maintenance so that the opening orifice is verified to have been removed, to specify an additional procedure to be included if the pressure boundary has been breached for maintenance, and to add steps to take and document as left measurements for valve parts and to verify tolerances with the vendor manual.
The additional corrective actions include:
- 2. Updating the Master Parts List databases and the Procurement Inventory Control System databases to be in alignment with the design change package (CR 97-2766-6).
- 3. Develop lessons learned for Engineering of design products and their effects of configuration control.
- 4. Develop lessons learned for Maintenance and Work Planners to ensure procedure adequacy in relation to vendor manuals.
- 5. Revise the STP procedure Outage Preparation and Implementation Guideline to evaluate the risk of operating a complete fuel cycle with a safety related component inoperable, despite allowance by a Technical Specification.
- 6. Perform a needs analysis on outage training for operations on Technical Specifications 4.0.5 and 4.4.10 and their application with Technical Specification 3.4.4 Action A during startup.
VI. Previous Similar Events
A previous similar event, PCV-0656A failed to open during surveillance testing, this was identified entering outage 1RE23 on October 9, 2021, at 0833. The failure was determined to be a result of mechanical rubbing between the valve plug and cage assembly with the cage assembly measurements being out of tolerance. Corrective actions from the previous event included replacing the solenoid, plug, cage, and seat. (CR 21-10369) 6 6
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