05000440/LER-2016-004, Regarding Loss of Safety Function Due to Two Inoperable Standby Liquid Control Subsystems
| ML17055C355 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 02/24/2017 |
| From: | Hamilton D FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-17-019 LER 16-004-00 | |
| Download: ML17055C355 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor |
| 4402016004R00 - NRC Website | |
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FirstEnergy Nuclear Operating Company David B. Hamilton Vice President February 24, 2017 L-17-019 A TIN: 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 10 CFR 50. 73(a)(2)(v)(A) 10 CFR 50. 73(a)(2)(v)(D)
Perry Nuclear Power Plant PO. Box 91 10 Center Road Perry, Ohio 44081 440-280-5382 Enclosed is Licensee Event Report (LER) 2016-004, "Loss of Safety Function Due to Two Inoperable Standby Liquid Control Subsystems." There are no regulatory commitments contained in this submittal.
If there are any questions or if additional information is required, please contact Mr. Nicola Conicella, Manager-Regulatory Compliance, at (440) 280-5415.
Sincerely, David B. Hamilton Vice President
Enclosure:
LER 2016-004 cc:
NRC Project Manager NRC Resident Inspector NRC Region Ill Regional Administrator
Enclosure L-17-019 LER 2016-004 Page 1 of 5
NRC FORM366 U.S. NUCLEAR REGULA TORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/20H (06-2016)
, the NRG may not conduct or sponsor, and a person is not required to respond lo, the infonmation collection.
3.PAGE Perry Nuclear Power Plant 05000 440 1 OF 4
- 4. TITLE:
Loss of Safety Function Due to Two Inoperable Standby Liquid Control Subsystems
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED I
SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR 05000 FACILITY NAME OOCKET NUMBER 12 28 2016 2016 -
004 00 02 24 2017 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
D 20.2201(b)
D 20.2203(aJ(3J(il D 50. 73(a)(2)(ii)(A)
D 50. 73(a)(2)(viii)(A) 1 D 20.2201(dl D 20.2203(aJ(3Hiil D 50. 73(a)(2)(ii)(B)
D 50.73(a)(2)(viii)(B)
D 20.2203(aJ<1l D 20.2203(aJ(4l D 50.73(aJ(2)(iiil D 50.73(a)(2)(ix)(A)
D 20.2203(a)(2J(il D 50.36(c)(1)(i)(A)
D 50.73(a)(2)(iv)(A)
D 50.73(a)(2)(x)
- 10. POWER LEVEL D 20.2203(aJ(2J(iil D 50.36(c)(1)(ii)(A)
IZ! 50. 73(a)(2)(v)(A)
D 73.71(a)(4l D 20.2203(a)(2)(iiil D 5o.36(c)(2l D 50.73(a)(2)(v)(B)
D 73.71(a)(5l D 20.2203(a)(2)(iv)
D so.46(a)(3)(ii)
D 50.73(a)(2)(v)(C)
D 73.77(a)(1l 098 D 20.2203(a)(2)(v)
D 50.73(a)(2)(i)(A) 181 50. 73(a)(2)(v)(D) 0 73.77(a)(2)(i)
D 20.2203(a)(2)(vi)
D 50. 73(a)(2)(i)(B)
D 50.73(a)(2)(vii) 0 73.77(a)(2)(ii) 0 50.73(a)(2)(i)(C)
D OTHER Specify in Abstract below or in YEAR 2016
- 3. LER NUMBER SEQUENTIAL NUMBER 004 from two to one. Since the other firing circuit was complete, discharge valve B would have operated as designed and supported chemical injection to the vessel if it received an initiation signal. However, Surveillance Requirement (SR) 3.1. 7.4, which verifies continuity of the explosive charges, was not met and on December 28, 2016 from 2229 hours0.0258 days <br />0.619 hours <br />0.00369 weeks <br />8.481345e-4 months <br /> to 2335 hours0.027 days <br />0.649 hours <br />0.00386 weeks <br />8.884675e-4 months <br />, with both systems declared inoperable, the system was administratively in a condition that rendered it unable to fulfill its safety function.
The event was isolated to a small section of the cable that connects the discharge valve to the 120 VAC power supply. The direct cause for the loss of continuity to one of the two firing circuits in discharge valve B was a loose connection between a pin and jack on the connector. The apparent cause of the event was the preventative maintenance (PM) scope did not have a step to inspect the condition of the pins and jack in this connection, which allowed the wear to go undetected until it was self-revealed via an equipment issue.
ANALYSIS OF EVENTS REV NO.
00 The safety function of the SLC system is to mitigate the consequences in the event that not enough control rods can be inserted in the reactor core to accomplish shutdown and cool-down in the normal manner, and to provide a pH buffering solution for injection into the reactor vessel suppression pool following a design basis LOCA. The system is manually initiated from the control room and consists of a boron solution tank, two positive displacement pumps and two explosive valves (discharge valves), which are provided in parallel for redundancy, and associated piping and valves used to transfer borated water from the storage tank to the reactor pressure vessel. The system is not a backup scram system for the reactor, but an independent backup system for the control rod drive (CRD) [AA] system. At the time of the event, the CRD system was operable and available.
Each discharge valve uses explosive charges as their opening mechanisms, which are electrically operated.
Each explosive charge contains two independent firing circuits, also known as primers, and a small electrical current continuously tests for continuity. For continuity testing, the charges are in series, therefore a break in any part of the circuit would break continuity and provide an out-of-service alarm in the control room. When called upon to function (i.e., fire the explosive charge), power is directed to the two independent firing circuits in parallel, meaning the electrical path for firing of the explosive charge is different than the electrical path for testing continuity.
A probabilistic risk assessment (PRA) evaluation of this event notes that the function of the Standby Liquid Control System remained available since discharge valve B would have operated as designed and supported chemical injection to the vessel. On this basis there would be no impact to the PRA model, and therefore no corresponding change (delta) in core damage frequency (CDF) and no corresponding change (delta) in large early release frequency (LERF). The delta CDF and delta LERF values are well below the acceptable thresholds of 1.0E-06/year and 1.0E-07/year, respectively, as discussed in Regulatory Guide 1.174. The risk of this event is therefore considered small in accordance with the regulatory guidance.
With both subsystems having been declared inoperable, this was determined to be a reportable event under 10 CFR 50.72(b)(3)(v)(A) and 10 CFR 50.72(b)(3)(v)(D) for an event or condition that that could have prevented the fulfillment of the safety function of structures or systems that are needed to shut down the reactor and maintain it in a safe shutdown condition and mitigate the consequences of an accident. As such, an event notification was made to the NRC Operations Center and recorded under Event Number 52468.
YEAR 2016
- 3. LER NUMBER SEQUENTIAL NUMBER 004 Although it was subsequently determined that SLC subsystem B would have functioned if called upon and thus the safety function would have been met, this event is being reported in accordance with 10 CFR 50.73(a)(2)(v)(A) and 10 CFR 50.73(a)(2)(v)(D), as follow-up to the 10 CFR 50.72(b)(3)(v)(A) and 10 CFR
- 50. 72(b)(3)(v)(D) notification made under Event Number 52468.
CORRECTIVE ACTIONS
The power supply cable was replaced and post maintenance testing was completed satisfactorily. The preventative maintenance procedure will be revised to include a step to inspect connection pins and jacks when changing the firing assembly.
Additionally, the cable on the discharge valve for SLC subsystem A will be replaced and sent to FirstEnergy BETA Laboratory for analysis when the valve is replaced during the next refueling outage. The analysis will be used to determine if a new preventative maintenance task is necessary for periodic replacement of these cables.
PREVIOUS SIMILAR EVENTS
A review of LERs and the corrective action database for the past three years showed no similar events.
REV NO.
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