05000293/LER-1917-008, Re 480V Bus B6 Auto Transfer Function Degraded Due to Time Delay Relay Failure

Re 480V Bus B6 Auto Transfer Function Degraded Due to Time Delay Relay Failure

ML17212A615
Person / Time
Site:	Pilgrim
Issue date:	06/30/2017
From:	Perkins E Entergy Nuclear Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2.17.048 LER 17-008-00
Download: ML17212A615 (7)

LER-1917-008, Re 480V Bus B6 Auto Transfer Function Degraded Due to Time Delay Relay Failure

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 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)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i)
2931917008R00 - NRC Website

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~Entergx June 30, 2017 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555-0001 Entergy Nuclear Operations, Inc.

Pilgrim Nuclear Power Station 600 Rocky Hill Road Plymouth, MA 02360

SUBJECT:

Licensee Event Report 2017-008-00, 480V Bus B6 Auto Transfer Function Degraded Due to Time Delay Relay Failure Pilgrim Nuclear Power Station Docket No. 50-293 Renewed License No. DPR-35 LETTER NUMBER:

2.17.048

Dear Sir or Madam:

The enclosed Licensee Event Report 2017-008-00, 480V Bus B6 Auto Transfer Function D'egraded Due to Time Delay Relay Failure, is submitted in accordance with Title 10 Code of Federal Regulations 50.73.

If you have any questions or require additional information', please contact me at (508) 830-8323.

There are no regulatory commitments contained in this letter.

Sincerely, Ev~i~:~k Manager, Regulatory Assurance EPP/sc Attachment: Licensee Event Report 2017-008-00, 480V Bus B6 Auto Transfer Function Degraded Due to Time Delay Relay Failure ( 4 pages)

Entergy Nuclear Operations, Inc.

Pilgrim Nuclear Power Station cc:

Mr. Daniel H. Dorman Regional Administrator, Region I

• U.S. Nuclear Regulatory Commission 2100 Renaissance Blvd., Suite 100 King of Prussia, PA 19406-2713 Mr. John Lamb, Senior Project Manager Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Stop 0-8C2A Washington, DC 20555 USNRC Senior Resident Inspector Pilgrim Nuclear Power Station Letter No. 2.17.048 Page 2 of 2

Attachment Letter Number 2.17.048 Licensee Event Report 2017-008-00 480V Bus 86 Auto Transfer Function Degraded Due to Time Delay Relay Failure (4 Pages)

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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 (04-2017) htto://www.nrc.govlreading-rmldoc-collectionslnur§9slstafflsr10221r3D the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME

12. DOCKET NUMBER

,3. PAGE Pilgrim Nuclear Power Station 05000-293 1 OF4

4. TITLE,480V Bus B6 Auto Transfer Function Degraded Due to Time Delay Relay Failure

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED SEQUENTIAL FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR REV MONTH DAY YEAR N/A NUMBER NO.

05000 N/A 05 03 2017 2017

- 008

- 00 06 30 2017 FACILITY NAME DOCKET NUMBER N/A 05000 N/A

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: Check all that apply)

N D 20.2201(b)

D 20.2203(a)(3)(i)

D 50.73(a)(2)(ii)(A)

D 50.73(a)(2)(viii)(A)

D 20.2201(d)

D 20.2203(a)(3)(ii)

D 50.73(a)(2)(ii)(B)

D 50.73(a)(2)(viii)(B)

D 20.2203(a)(1)

D 20.2203(a)(4)

D 50.73(a)(2)(iii)

D 50.73(a)(2~(ix)(A)

D 20.2203(a)(2)(i)

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(a)(2)(ii)

D 50.36(c)(1)(ii)(A)

D 50.73(a)(2)(v)(A)

D 73.71(a)(4)

D 20.2203(a)(2)(iii)

D 50.36(c)(2)

[gl 50.73(a)(2)(v)(B)

D 73.71(a)(5) 0 D 20.2203(a)(2)(iv)

D 50.46(a)(3)(ii)

[gl 50.73(a)(2)(v)(C)

D 73.77(a)(1)

D 20.2203(a)(2)(v)

D 50.73(a)(2)(i)(A)

[gl 50.73(a)(2)(v)(D)

D 73.77(a)(2)(i)

D 20.2203(a)(2)(vi)

[gl 50.73(a)(2)(i)(B)

D 50.73(a)(2)(vii)

D 73.77(a)(2)(ii)

('

D 50.73(a)(2)(i)(C) 0 OTHER Specify in Abstract below or in SEQUENTIAL NUMBER

- 008 REV NO.

- 00 Thus, with contact 3/5 of relay 27A-B1 X/TDDO opening instantaneously instead of with a time delay, this portion of the transfer scheme to transfer Bus B6 to Bus B2 with Bus B1 powering Bus B6 and a degraded voltage on Bus B1 was inoperable.

However, the ability to perform a manual operation to transfer Bus B6 from Bus B1 to Bus B2 on a Bus B1 degraded voltage condition per Pilgrim Nuclear Power Station (PNPS) procedure 2.4.B.6, "Loss of Bus B6" was available. This transfer would re-power the LPCI injection valves and provide power to primary containment isolation valves.

CAUSE OF THE EVENT

The cause of the failure of time delay relay 27A-B11<fTDDO is indeterminate at this time. This relay has been sent to an offsite vendor for further testing and analysis.

CORRECTIVE ACTIONS

The Agastat time delay relay 27A-B1X/TDDO was replaced, restoring the degraded voltage protection functionality for the condition where Bus 86 is being powered by Bus B1.

Forensic testing is being performed on the removed relay. Any additional corrective actions will be entered into the PNPS Corrective Action Program.

SAFETY CONSEQUENCES

This condition was discovered during the refueling outage when conditions were such that the equipment normally energized/activated by this time delay relay were not required to be operable and there is no firm evidence that it existed during plant operation.

If it did exist during plant operation and a Bus B1 degraded voltage condition had occurred, manual actions could have been taken to transfer Bus B6 from Bus B1 to Bus B2 per procedure PNPS 2.4.B.6, "Loss of Bus B6." This transfer would re-power the LPCI injection valves and provide power to other primary containment isolation valves.

There are no consequences to the general safety of the public, nuclear safety, industrial safety and radiological safety from this event.

REPORT ABILITY YEAR 2017 SEQUENTIAL NUMBER

- 008 REV NO.

- 00 Pilgrim Nuclear Power Station is submitting this Licensee Event Report (LER) in accordance with 10 CFR 50.73(a)(2)(i)(B)- Operation or condition prohibited by Technical Specifications; and potentially in accordance with10 CFR 50. 73(a)(2)(v)(B), (C) and (D) - Any condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to remove residual heat, control the release of radioactive material and mitigate the consequences of an accident, although there is no firm evidence to support that the relay failure occurred before discovery. This LER will be updated following further evah,iation of the cause of the failure.

PREVIOUS EVENTS A review of PNPS LERs for the past five years identified LER 2015-004-00, "480V Bus B6 Auto Transfer Function Degraded" also documented a failure of relay 27A-B1X/TDDO. In the 2015 failure, the relay contact 3/5 never closed to initiate the transfer logic to trip open Breaker 52-601 and close Breaker 52-602.

REFERENCES:

CR-PNP-2017-4768 CR-PNP-2015-3454 NRC FORM 3668 (04-2017)