05000277/LER-2022-002, Automatic Depressurization System Safety Relief Valve Actuator Diaphragm Degraded

Automatic Depressurization System Safety Relief Valve Actuator Diaphragm Degraded

ML22349A084
Person / Time
Site:	Peach Bottom
Issue date:	12/15/2022
From:	Henry D Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
CCN: 22-89 LER 2022-002-00
Download: ML22349A084 (1)

LER-2022-002, Automatic Depressurization System Safety Relief Valve Actuator Diaphragm Degraded

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2772022002R00 - NRC Website

text

10 CFR 50.73 CCN: 22-89 December 15, 2022 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station (PBAPS) Unit 2 Subsequent Renewed Facility Operating License No. DPR-44 NRC Docket No. 50-277

Subject:

Licensee Event Report (LER) 2022-002-00 Automatic Depressurization System Safety Relief Valve Actuator Diaphragm Degraded The subject report is being submitted in accordance with 50.73(a)(2)(i)(B) for any operation or condition which was prohibited by the plants Technical Specifications.

There are no commitments contained in this letter. If you have any questions, please contact the Peach Bottom Regulatory Assurance Manager, Mr. Wade Scott at (717) 456-3047.

Respectfully, David A. Henry Site Vice President Peach Bottom Atomic Power Station Enclosure cc:

USNRC, Administrator, Region I USNRC, Senior Resident Inspector W. DeHaas, Commonwealth of Pennsylvania S. Seaman, State of Maryland B. Watkins, PSE&G, Financial Controls and Co-Owner Affairs

Abstract

On October 17, 2022, with the unit in a refueling outage. Water was identified leaking from a fastener on the PB2 RV-71B Main Steam Safety/Relief Valve (S/RV) body. The water leak was a small steady stream. The leakage was due to a degraded gasket and steam cut fastener threads. Subsequent laboratory analysis of the leaking valve identified the Automatic Depressurization System, (ADS) function performed by the pneumatic operator was non-functional.

The pneumatic operator resilient components (diaphragm) were discovered to be embrittled and lost pressure retaining integrity. The timeframe for the degraded ADS capability cannot be reasonably determined at this time. The relief valve overpressure function was evaluated to be not impacted by the leak or the loss of ADS function.

Therefore, Peach Bottom is submitting this report in accordance with 10 CFR 50.73(a)(2)(i)(B), as any operation or condition which was prohibited by the plants Technical Specifications, having exceeded the required 14 day action time or maximum Risk Informed Completion Time (RICT) to restore an ADS valve to OPERABLE status.

There were no other systems which were inoperable during this identified condition that contributed to this event.

There were no actual safety consequences as a result of this event.

(See Page 3 for required number of digits/characters for each block)

(See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1022/r3/)

Page 4 of 4 Leakage past the fastener threads compromised the pilot filter plug outer gasket enabling a flow path for main steam to enter into the drywell. The small volume steam leak impinged on the relief valve insulation blankets and wet vapor flow exited the metal enclosure opening through which the pneumatic operator protrudes. The wet vapor flow exiting the metal enclosure aperture subjected the pneumatic operator to elevated operating temperatures. Over some indeterminate time period following its last observed operation in May 2022, the operator diaphragm was adversely impacted. The diaphragm as-found condition was typical of sustained exposure to temperatures above its material qualifications. No human performance related causes have been identified.

Corrective Actions

RV-71B was replaced in kind with a refurbished, tested and fully qualified replacement S/RV prior to unit start up from the refueling outage (P2R24) and entry into the mode of applicability for TS 3.4.3 and 3.5.1.

All other S/RVs were visually inspected for proper insulation installation and any evidence of steam leaks from their respective pilot filter fasteners and other bolting. In addition, all S/RV pneumatic operators were tested in-situ to validate full function and integrity of the pneumatic operator resilient parts. S/RVs replaced within the planned maintenance scope of the refueling outage (RV-71G,, RV-71J, RV-71K) also underwent review of the refurbishment and testing work package documentation to ensure pilot filter fastener and gasket tolerances were within design limits. No further deficiencies were identified.

The failed resilient parts shall undergo analysis to ensure compliance with applicable design specifications.

Causal evaluation results will be reviewed by refurbishment vendor and the original equipment manufacturer.

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