05000278/LER-2023-001, Standby Liquid Control Pump Inoperable for Greater than LCO Window Due to Gas Intrusion

Standby Liquid Control Pump Inoperable for Greater than LCO Window Due to Gas Intrusion

ML23311A061
Person / Time
Site:	Peach Bottom
Issue date:	11/07/2023
From:	Searer J Constellation Energy Generation
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
CCN: 23-78 LER 2023-001-00
Download: ML23311A061 (4)

LER-2023-001, Standby Liquid Control Pump Inoperable for Greater than LCO Window Due to Gas Intrusion

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2782023001R00 - NRC Website

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10 CFR 50.73 CCN : 23-78

November 7, 2023

U.S. Nuclear Regulatory Commission ATTN : Document Control Desk Washington, DC 20555-0001

Peach Bottom Atomic Power Station (PBAPS) Unit 3 Subsequent Renewed Facility Operating License No. DPR-56 NRC Docket No. 50 - 278

Subject: Licensee Event Report (LER) 2023-001-00 Standby Liquid Control Pump Inoperable for Greater than LCO Window due to Gas Intrusion

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 plant's 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) 456-304 7.

Respectfully, 4-,r:2-Jeremy C. Searer Acting Plant Manager 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 September 9, 2023, during performance of a functional test, the Unit 3 B Standby Liquid Control Pump did not produce discharge pressure. The pump was declared inoperable and Technical Specification Limiting Condition for Operation (LCO) 3.1.7 Condition B was entered. Troubleshooting identified that the pump and part of the discharge piping was not sufficiently filled with water. The most likely source of gas intrusion was the nitrogen filled accumulator located on the discharge piping between the pump and the discharge check valve. The piping was refilled and the accumulator was replaced, after which the pump was run successfully. The system was restored to operable and the LCO was exited on September 12, 2023. The gas leakage rate was slow and therefore, the system was likely inoperable longer than the LCO-allowed outage time (i.e., 7 days).

Therefore, the condition is being reported under 10CFR 50.73(a)(2)(i)(B). 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.

Event Description

On September 9, 2023, during performance of a functional test, the Unit 3 B Standby Liquid Control (SLC, EIIS: BR) Pump (EIIS: P) did not produce discharge pressure. T he pump was declared inoperable and Technical Specifications (TS) Limiting Condition for Operation (LCO) 3.1.7 Condition B was entered at 20:32 hours. Troubleshooting identified that the pump and part of the discharge piping was not sufficiently filled with water. The most likely source of gas intrusion was a leaking bladder inside the pneumatic-hydraulic accumulator (EIIS: ACC). The device is installed on the piping near the SLC pump discharge relief valve to dampen pulsations from the pumps to protect the system piping. Nominal accumulator pressure is between 325 psig and 450 psig. The accumulator bladder was replaced, a fter which the pump and discharge piping were filled and the pump was run successfully. The system was restored to operable and the LCO was exited on September 12, 2023 at 17:39 hours.

At the time of discovery, Unit 3 was operating in MODE 1 at approximately 91% power, due to end-of-cycle coast down.

Peach Bottom TS LCO 3.1.7 Required Action B.1 requires that a S LC subsystem be restored to operable status within 7 days or in accordance with the Risk Informed Co mpletion Time Program. If this action is not met, the plant is required to be in MODE 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and MODE 4 within 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

The most likely cause of the condition is gas leakage through the accumulator bladder. The estimated leak rate was small, because no visible sources of leakage were foun d on the accumulator bladder and the rate of pressure decay within the accumulator was slow. Failure analys is is being performed on the bladder, but at this time, the exact cause of the leakage is unknown. The 3B S LC subsystem was last run successfully on May 29, 2023. Trending of available accumulator pressure data did not provide a conclusive time of failure.

Due to the slow nature of the leakage and the volume of gas intrusion present, it is highly likely that the condition existed longer than the LCO-allowed outage time.

Since the 3B train of SLC was likely inoperable for greater than the LCO-allowed outage time, this condition is being reported under 10CFR 50.73(a)(2)(i)(B).

The Energy Industry Identification System component function identifier and name of each component or system:

EIIS: Standby Liquid Control System, BR 3BT076, Standby Liquid Control N2 Accumulator Manufacturer: Greer Hydraulics, Inc Model: A68514-200

Safety Consequences

The SLC System is designed to provide the capability of bringin g the reactor, at any time in a fuel cycle, from full power and minimum control rod inventory (which is at the p eak of the xenon transient) to a subcritical condition with the reactor in the most reactive, xenon free state without taking credit for control rod movement.

The SLC System satisfies the requirements of 10 CFR 50.62 on an ticipated transient without scram using highly enriched boron. The SLC System is also used to maintain suppression pool pH at or above 7 following

a loss of coolant accident (LOCA) involving significant fission product releases. The SLC system consists of two redundant trains, either of which is sufficient to perform its safety function.

There were no other systems which were inoperable during this identified condition. The 3A SLC train demonstrated full functional capability by performance of a surveillance test on September 3, 2023. There were no actual safety consequences as a result of this event, b ecause the redundant train maintained operability.

Corrective Actions

The Unit 3 B SLC accumulator bladder was replaced to restore the subsystem to full function. Investigation into the cause of the bladder leakage is ongoing. If the results of this investigation substantially change the assessment of this condition or planned corrective actions, a s upplement to this LER will be submitted.

The remaining SLC discharge lines (2A, 2B, and 3A) were examine d by ultrasonic testing on October 9, 2023.

All three discharge lines contained gas voids, which were significantly less than what was discovered on the 3B line. None of the discovered gas voids extended to the pump casings or internals. The 3A pump was operated with gas voids present, successfully demonstrating tha t this volume of gas intrusion posed no adverse impact to the pump function. The 3B pump was also examined at this time, and the piping was full of water. The SLC pump discharge process piping will be periodica lly monitored until replacement accumulator bladders can be procured and installed.

Previous Similar Events

Peach Bottom has not previously experienced a failure of a SLC system accumulator bladder that adversely impacted pump performance.