05000293/LER-2017-005

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LER-2017-005, 10 CFR 50, Appendix J, Option B, Leak Rate Criteria Exceeded
Pilgrim Nuclear Power Station
Event date: 04-10-2017
Report date: 06-07-2017
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications

10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded

10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident

10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material
LER closed by
IR 05000293/2017004 (14 February 2018)
2932017005R00 - NRC Website
LER 17-005-00 for Pilgrim Regarding 10 CFR 50, Appendix J, Option B, Leak Rate Criteria Exceeded
ML17171A276
Person / Time
Site: Pilgrim Entergy icon.png
Issue date: 06/07/2017
From: Perkins E P
Entergy Nuclear Operations
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
2.17.043
Download: ML17171A276 (6)


comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

Pilgrim Nuclear Power Station 05000-293 2017 - 00 - 005

BACKGROUND

The safety objective of the Primary Containment System is to provide the capability in conjunction with other safeguard features to limit the release of fission products in the event of a postulated design basis accident (DBA) so that offsite doses would not exceed the guideline values set forth in 10 Code of Federal Regulation (CFR) 100 and to prevent excessive fuel cladding temperatures.

EVENT DESCRIPTION

On April 10, 2017, the Personnel Airlock, X-2, failed to meet local leak rate test (LLRT) acceptance criteria of 0.05La (10.25 Standard Liters per Minute (SLM)) during the as-found LLRT.

On April 22, 2017, the High Pressure Coolant Injection (HPCI) turbine exhaust line check valves, 2301-74 and 2301- 45, both failed to meet LLRT acceptance criteria. The test volume for each valve could not be pressurized to test pressure when flow was greater than 100 SLM. Significant air flow was observed to be coming out of the test vent, indicating that each check valve was either degraded or not seated. The turbine exhaust line check valves must open during HPCI turbine operation. The valves also must close promptly upon reverse flow.

The HPCI check valves satisfied the leak rate test acceptance criteria in May 2015 during Refueling Outage (RFO) 20. Although unlikely that both valves failed shortly after RFO 20, without any data to determine the time of the failures, the primary containment function of Penetration X-223 was declared inoperable over the entire operating cycle between RFO 20 and RFO 21. Check valve leakage greater than 100 SLM results in exceeding the overall Technical Specification (TS) as-found minimum path Appendix J acceptance criteria (126.3 SLM).

During the current RFO, summation of Type B and Type C testing results exceeded the 10 CFR 50, Appendix J, LLRT criteria limit of 0.6 La and the primary containment total leakage criteria limit of 1.0 La.

Because of data collected during RFO 21 regarding Appendix J, LLRT, retrospectively two main steam isolation valves (MSIV) penetrations, X-7D Main Steam Line D pathway and X-7C Main Steam Line C pathway each exceeded their TS Leakage Limit during part of Operating Cycle 21 between May 2015 and December 2016. The leakage through the X-7C Pathway also exceeded the 1.0 La leakage limit. The MSIV penetration leakage is being addressed in a supplement to LER 2016-010-00.

CAUSE OF THE EVENTS

The personnel airlock, X-2, failure was due to the displacement of the 0-ring(s) on the inner pressure equalizing device (PED). The airlock PED 0-ring(s) were replaced, correcting the leakage condition of the inner containment barrier. Once the PED 0-ring(s) were replaced, the integrated airlock leak rate test was re-performed to verify the as- found outboard airlock barrier leakage results demonstrated that the primary containment personnel airlock was capable of performing the radioactive material barrier safety function.

The HPCI turbine exhaust line check valves both failed to meet LLRT acceptance criteria. The test volume could not be pressurized when flow was greater than 100 SLM. Subsequent disassembly and inspection showed that the inboard (2301-74) check valve was not fully seating in the closed position, and the outboard (2301-45) check valve had internal degradation that prevented the valve disk from closing properly.

comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

Pilgrim Nuclear Power Station 05000-293 2017 - 00 - 005

CORRECTIVE ACTIONS

The HPCI turbine exhaust check valves, the MSIVs, and the containment personnel airlock PED were all repaired and subsequently retested, declared Operable and returned to service.

SAFETY CONSEQUENCES

The actual consequences of the two HPCI turbine exhaust check valves were a primary containment loss of safety function. Since two of the four inboard MSIVs failed their respective LLRTs, then, it is assumed that at least some time during Operating Cycle 21 there may have been a pathway from primary containment via two of the main steam lines, into secondary containment (the main stream line tunnel area) whose atmosphere is filtered through Standby Gas Treatment. The personnel airlock interior boundary failed but the exterior boundary was intact to perform the safety function. No actions to reduce the frequency or consequence are necessary.

REPORTABILITY

During the current RFO, summation of Type B and Type C testing results exceeded the 10 CFR 50, Appendix J, LLRT criteria limit of 0.6 La and the primary containment total leakage criteria limit of 1.0 La. This created an event that is reportable under 10 CFR 50.73(a)(2)(i)(B), any operation or condition which was prohibited by the plant's Technical Specifications and 10 CFR 50.73(a)(2)(ii)(A), any event or condition that resulted in the condition of the nuclear power plant, including its principal safety barriers, being seriously degraded, as well as 10 CFR 50.73(a)(2)(v)(C), any condition that could have prevented the fulfillment of a safety function of a system needed to control the release of radioactive material, and 10 CFR 50.73(a)(2)(v)(D), any condition that could have prevented the fulfillment of a safety function of a system needed to mitigate the consequences of an accident.

This submittal also addresses the personnel airlock which did not meet its local leak rate test leakage acceptance criteria limit of 0.05La. This also created a situation that is reportable under 10 CFR 50.73(a)(2)(i)(B), any condition which was prohibited by the plant's TS.

PREVIOUS EVENTS

A review of Pilgrim Nuclear Power Station LERs for the last 10 years did not find a similar event as described in this LER. However, there was a previous personnel airlock PED failure in 2013 as reported in CR-PNP-2013-2276.

REFERENCES:

CR-PNP-2017-3184 CR PNP-2017-4047 CR PNP-2017-4048 CR-PNP-2017-3531 CR-PNP-2017-3588 CR-PNP-2017-5075