05000440/LER-2022-001, Low Pressure Core Spray Inoperable Due to Loss of Minimum Flow Valve
| ML22229A090 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 08/17/2022 |
| From: | Penfield R Energy Harbor Nuclear Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-22-173 LER 2022-001 | |
| Download: ML22229A090 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 4402022001R00 - NRC Website | |
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perry Nuclear Power Plant 10 Center Road Perry, Ohio 44081 Rod L. Penfleld 440-280-5382 Site Vice President, Perry Nuclear 724-462-0816 (cell)
August 17, 2022 L-22-173 10 CFR 50.72(b)(3)(v)(D)
ATTN:
Document Control Desk U. S. Nuclear Regulatory Commission Washington, DC 20555-0001
SUBJECT:
Perry Nuclear Power Plant Docket No. 50-440, License No. NPF-58 Licensee Event Report Submittal Enclosed is Licensee Event Report (LER) 2022-001, "Low Pressure Core Spray Inoperable due to Loss of Minimum Flow Valve."
There are no regulatory commitments contained in this submittal.
If there are any questions or if additional information is required, please contact Mr. Glendon Burnham, Manager-Regulatory Compliance, at (440) 280-7538.
Rod L. Penfield
Enclosure:
LER 2022-001 cc:
NRC Project Manager NRC Resident Inspector NRC Region III Regional Administrator
Enclosure L-22-173 LER 2022-001
Abstract
On June 24, 2022, at 1257 hours0.0145 days <br />0.349 hours <br />0.00208 weeks <br />4.782885e-4 months <br />, the Low Pressure Core Spray (LPCS) system was declared INOPERABLE due to a loss of power to the pump minimum flow valve. Since LPCS is a single train safety system as specified in site procedures, LPCS inoperability is considered a loss of safety function and is reportable.
The cause for LPCS inoperability is the failure of the minimum flow valve actuator to valve bonnet bolts.
The most probable cause of the failed adapter to actuator bolts was fatigue failure.
The bolting and the fuses have been sent to a laboratory for further analysis.
Corrective actions included replacement of the valve actuator motor and the mounting bolts.
Laboratory analysis may necessitate additional corrective actions once the results are known, in which case an LER revision will be submitted.
The safety significance of this event is considered to be very small. This event is being reported in accordance with 10 CFR 50.73(a)(2)(v)(D) as an event or condition that could have prevented the fulfillment of a safety function needed to mitigate the consequences of an accident.
Energy Industry Identification System (EMS) codes are identified in the text as [XX].
INTRODUCTION
The inoperability and loss of safety function of Low Pressure Core Spray (LPCS) [BM] system occurred as a result of a loss of electrical power to the LPCS pump minimum flow valve [FCV] based upon the receipt of unexpected alarms in the Control Room, during surveillance testing. Subsequent investigation of the LPCS minimum flow valve revealed that the mounting bolts for the motor operated valve actuator were broken, and the fuses [FU] in the disconnect for the actuator were found to be blown. With LPCS being a single train safety system, this resulted in a loss of safety function resulting in a 10 CFR 50.72 notification and a 10 CFR 50.73 report.
EVENT DESCRIPTION
On June 24, 2022, at 1257 hours0.0145 days <br />0.349 hours <br />0.00208 weeks <br />4.782885e-4 months <br />, and with the reactor in MODE 1
at 100 percent rated thermal power, a surveillance was being performed to verify the operation of the LPCS system. During performance of the surveillance, it was observed that the LPCS minimum flow valve experienced a loss of position indication while stroking closed. Upon investigation of the Motor Control Center (MCC) disconnect [DISC] for the LPCS minimum flow valve, it was determined that two of three main-line power fuses were blown. Examination of the LPCS minimum flow valve revealed that the motor-operated actuator had become separated from the valve.
This resulted in the LPCS system being declared inoperable.
LPCS is described as a single train safety system in accordance with site procedures.
As such, when LPCS has an unplanned inoperability, it is reportable to the NRC under 10 CFR 50.72(b)(3)(v)(D) and 10 CFR 50.73(a)(2)(v)(D) as a Loss of Safety Function.
On June 24, 2022, at 1628 hours0.0188 days <br />0.452 hours <br />0.00269 weeks <br />6.19454e-4 months <br />, Event Notification (EN 55962) was made under 10 CFR 50.72(b)(3)(v)(D) to the NRC. This Licensee Event Report is being reported under 10 CFR 50.73(a)(2)(v)(D) as a loss of safety function.
New actuator to valve bolts, a new actuator motor, and new disconnect fuses were installed for the LPCS minimum flow valve. The system performed satisfactorily during post maintenance testing. LPCS was declared OPERABLE on June 27, 2022, at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />.
CAUSE OF EVENT
The most probable cause of the failed adapter to actuator bolts was fatigue failure.
The bolting and the fuses have been sent to a laboratory for further analysis.
Based upon the information from the analyses, an LER revision may need to be submitted.
EVENT ANALYSIS
A Probabilistic Risk Assessment (PRA) evaluation was performed for the June 24, 2022, LPCS Minimum Flow Valve Inoperability event. Fire and other external hazards were qualitatively addressed to be of low risk. The analysis of this eveni results in delta CDF and delta LERF values that are below the acceptable thresholds of 1.OE-06/yr and 1.OE-07/yr, as discussed in Regulatory Guide 1.174. Sensitivities performed that varied the exposure window to the maximum possible exposure window of one year did not change these conclusions. The risk of this event is therefore considered very small in accordance with the Regulatory Guidance.
CORRECTIVE ACTIONS
The valve actuator was re-installed to the valve with new bolts. The actuator motor was also replaced.
New fuses were installed in the electrical disconnect.
The failed bolts and fuses have been sent out for laboratory analysis.
PREVIOUS SIMILAR EVENTS
None
COMMITMENTS
None(08-2020)
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