05000440/LER-2020-002, Standby Liquid Control System Rendered Inoperable Due to Valve Misposition
| ML20293A204 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 10/16/2020 |
| From: | Payne F Energy Harbor Nuclear Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-20-247 LER 2020-002-00 | |
| Download: ML20293A204 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| 4402020002R00 - NRC Website | |
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harbor Frank R. Payne Site Vice President, Perry Nuclear October 16, 2020 L-20-247 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 Energy Harbor Nuclear Corp Perry Nuclear Power Plant JO Center Road P.O. Box 97 Perry, Ohio 44081 440-280-5382 440-392-4723 (cell) 10 CFR 50. 73(a)(2)(v)(A) 10 CFR 50. 73(a)(2)(v)(D)
Enclosed is Licensee Event Report (LER) 2020-002, "Standby Liquid Control System Rendered Inoperable due to Valve Misposition." 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.
Sincerely,
Enclosure:
LER 2020-002 cc:
NRC Project Manager NRC Resident Inspector NRC Region Ill Regional Administrator
Abstract
On August 20, 2020, while performing testing on the Standby Liquid Control (SLC) system, water was inadvertently added to the SLC storage tank causing an unintended dilution of the boron solution. On August 21, 2020 at 0953 hours0.011 days <br />0.265 hours <br />0.00158 weeks <br />3.626165e-4 months <br />, sampling of the boron solution concentration revealed that Technical Specification (TS) Limiting Condition of Operation (LCO) 3.1.7 was not met, and Action Condition B was entered for two SLC subsystems INOPERABLE. Boron addition and sampling were performed, with SLC returning to OPERABLE on August 21, 2020 at 1307.
The direct cause of the unintentional addition of water to the SLC Storage Tank during testing was a valve mis-position due to human error. A corrective action will add independent verification to the procedure for closing of the Transfer Line Isolation valve.
The safety significance of this event is considered to be of very low safety significance, in accordance with the Regulatory Guidance. This event is reported in accordance with 10 CFR 50. 73(a)(2)(v)(A) and 10 CFR 50. 73(a)(2)(v)(D) as an event or condition that prevented the fulfillment of the safety function of the Standby Liquid Control System.
~nergy Industry Identification System (EIIS) codes are identified in the text as [XX].
NTRODUCTION YEAR 2020 -I SEQUENTIAL REV NUMBER NO.
002
- - I 00 fhe purpose of the Standby Liquid Control (SLC) System [BR] is to provide an alternate method of shutting down the reactor, ndependent of the Control Rod Drive System [AA]. This is accomplished by pumping a neutron absorbing solution into the
~eactor in sufficient concentration and quantity to provide the required shutdown margin without control rod movement and to
)vercome the maximum positive reactivity resulting from cooldown and xenon decay.
- VENT DESCRIPTION
)n August 20, 2020, while the plant was at 100 percent rated thermal power, Periodic Test Instruction, PTI-C41-P0001, 3tandby Liquid Control Transfer System Pump and Valve Operability Test, was being performed on the Standby Liquid
- ontrol (SLC) system. During the test, the Transfer Line Isolation valve [ISV], was directed to be closed, but instead was left
)pen due to a human performance error by a plant operator. The error led to the inadvertent addition of approximately 226
~allons of demineralized water to the existing 4872 gallons of boron solution in the SLC Storage Tank [TK]. Subsequently,
)reparations were made to perform sampling of the boron solution in the tank to verify SLC system operability.
)n August 21, 2020, at 0953 hours0.011 days <br />0.265 hours <br />0.00158 weeks <br />3.626165e-4 months <br />, while the plant was at 100 percent rated thermal power, the SLC system was declared NOPERABLE due to the sample for the SLC storage tank boron solution concentration not meeting Technical Specification TS) criteria. Condition B of TS 3.1.7 was entered for two SLC subsystems being INOPERABLE.
3LC was declared OPERABLE on August 21, 2020 at 1307 hours0.0151 days <br />0.363 hours <br />0.00216 weeks <br />4.973135e-4 months <br />, following boron addition to the SLC Storage Tank and
- ample verification that the boron solution concentration was within TS limits.
- AUSE
)irect Cause:
fhe direct cause of the unintentional addition of approximately 226 gallons of water to the SLC Storage Tank during the
- ,erformance of PTI-C41-P0001 was a valve mis-position due to human error. A procedure step in the PTI directed the Non-
,...icensed Operator (NLO) to Unlock and Close the Transfer Line Isolation valve. The NLO unlocked the valve but failed to close the valve. A subsequent step opened the Transfer Line Outboard Containment Isolation valve aligning the discharge of he running transfer pump to the SLC Storage Tank, which caused the Storage Tank to fill with water from the Transfer Tank.
IContributing Cause:
A contributing cause to the event was a latent procedural risk evaluation error that occurred in 2011. The Maintenance Plan or PTI-C41-P0001 was classified as a GREEN RISK activity, however, a single error resulted in the inoperability of a safety
- wstem. Per procedure NOP-OP-1007, Risk Management, an "activity if performed incorrectly (i.e. any single unrecoverable 1error) that would cause a loss or defeat of a safety system. If yes, this activity shall be Yellow Risk". Had the PTI been 1Classified as a Yellow Risk activity, increased oversight and monitoring usually associated with Yellow Risk activities may nave eliminated or minimized the impact of the error.
~ subsequent interview with the NLO found that there was no time or situational pressure related to the incident.
=VENT ANALYSIS REV NO.
- - I 00 rhe event was reported to the Nuclear Regulatory Commission (NRC) on August 21, 2020 at 1242 hours0.0144 days <br />0.345 hours <br />0.00205 weeks <br />4.72581e-4 months <br />, as an event or 1c;ondition that at the time of discovery could have prevented the fulfillment of a system needed to shut down the reactor and
~aintain it in a safe shutdown condition (10 CFR 50.72(b)(3)(v)(A)), and mitigate the consequences of an accident (10 CFR
- 50. 72(b )(3)(v)(D)).
. ~ Probabilistic Risk Assessment (PRA) evaluation was performed for the August 21, 2020 Standby Liquid Control noperability event. The analysis of this event results in delta Core Damage Frequency (CDF) and delta Large Early Release Frequency (LERF) values that are well below the acceptable thresholds of 1.0E-06/yr and 1.0E-07/yr, as discussed n Regulatory Guide 1.17 4, An Approach for using Probabilistic Risk Assessment in Risk Informed Decisions on Plant-Specific Changes to the Licensing Basis. Therefore, this event is considered to be of very low safety significance in
,accordance with the Regulatory Guidance.
A Reactor Engineering evaluation was performed, following the event. The analysis showed that the reactor would have Deen shut down had the SLC tank been injected with a 2.6% boron concertation with sufficient margin to the analytical "equirement. As such, the reactor would have been shut down with the measured SLC tank boron concentration of 2. 73%.
rhis event is reportable under 10 CFR 50. 73(a)(2)(v)(A) and 10 CFR 50. 73(a)(2)(v)(D) as an event or condition that orevented the fulfillment of the safety function of the Standby Liquid Control System.
- ORRECTIVE ACTIONS fhe immediate corrective action for the personnel error was handled through station performance management.
I~
planned corrective action will change procedure PTI-C41-P0001 to add an independent verification step for the closure of he Transfer Line Isolation valve.
rREVIOUS SIMILAR EVENTS t
review of Condition Reports for the past three years was performed, and no similar issues were identified.
- OMMITMENTS
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