05000423/LER-2016-002, Regarding Feedwater Isolation Signal Defeated Due to Wiring Error

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Regarding Feedwater Isolation Signal Defeated Due to Wiring Error
ML16092A068
Person / Time
Site: Millstone 
Issue date: 03/23/2016
From: Daugherty J
Dominion Nuclear Connecticut
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
16-067 LER 16-002-00
Download: ML16092A068 (6)
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LER-2016-002, Regarding Feedwater Isolation Signal Defeated Due to Wiring Error
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
LER closed by
IR 05000245/2016002 (25 July 2016)
4232016002R00 - NRC Website
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text

Dominion Nuclear Connecticut, Inc.

Rope Ferry Rd., Waterford, CT 06385 Mailing Address: P. 0. Box 128 Waterford, CT 06385 dam.com U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 DOMINION NUCLEAR CONNECTICUT, INC.

MILLSTONE POWER STATION UNIT 3 LICENSEE EVENT REPORT 2016-002-00 MAR 2 3 2016 Serial No.

MPS Lic/AVM Docket No.

License No.16-067 RO 50-423 NPF-49 FEEDWATER ISOLATION SIGNAL DEFEATED DUE TO WIRING ERROR This letter forwards Licensee Event Report (LER) 2016-002-00 documenting a condition discovered at Millstone Power Station Unit 3, on January 25, 2016. This LER is being submitted pursuant to 10 CFR 50.73(a)(2)(i)(B) as any operation or condition that is prohibited by the plant's Technical Specifications.

If you have any questions or require additional information, please contact Mr. Thomas G.

Cleary at (860) 444-4377.

Sincerely,

/}~

JohvR. Daugherty Site Vice President - Millstone Attachments: 1 Commitments made in this letter: None

cc:

U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd.

Suite 100 King of Prussia, PA 19406-2713 RV. Guzman NRC Project Manager Millstone Unit 2 and 3 U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 C-2 Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station Serial No.16-067 Docket No. 50-423 Licensee Event Report 2016-002-00 Page 2 of 2

ATTACHMENT Serial No.16-067 Docket No. 50-423 Licensee Event Report 2016-002-00 LICENSEE EVENT REPORT 2016-002-00 FEEDWATER ISOLATION SIGNAL DEFEATED DUE TO WIRING ERROR MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC.

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BYOMB: NO. 3150-0104 EXPIRES: 1013112018 (11-2015)

, the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.

6. LER NUMBER
3. PAGE YEAR I SEQUENTIAL I REV NUMBER NO.

3 OF 3

2016 002 -

00 average reactor coolant temperature, TAVE* In addition, the main feedwater pumps are automatically tripped following a safety injection signal or a reactor trip.

While being able to fulfill the safety function, the diverse methods of isolating main feedwater would not act as rapidly as closure of the main feedwater isolation valves. There is margin between the safety analysis results Final Safety Analysis Report (FSAR Chapter 15) and containment analysis results (FSAR Chapter 6) and the ultimate event acceptance criteria of the events to accommodate the slightly longer isolation function.

With three redundant methods capable of isolating/stopping main feedwater flow, the unavailability of one individual method (i.e., the automatic closure of 'C' FWIV) results in an insignificant increase in the likelihood of failing the safety function. Consequently, the safety significance associated with exceeding the 'C' FWIV TS allowed outage time is very low.

4. CORRECTIVE ACTION

The jumper was removed and the appropriate surveillance for FWIV 3FWS*CTV41 C was performed and completed satisfactorily, verifying the valve is OPERABLE. Other feedwater system components were inspected and no additional installed jumpers were identified. Workers involved were coached concerning the need for compliance with work control procedures and standards. This event will be used as operating experience (OE) for activities associated with installation and removal of jumpers.

5. PREVIOUS OCCURRENCES

There are no previous occurrences with the same underlying reason or consequences.

6. ENERGY INDUSTRY IDENTIFICATION SYSTEM (EllS) CODES:
  • Containment-NH
  • Isolation Valve - ISV
  • Pump-P
  • Solid State Protection System -JG
  • Steam Generator-SG

1. EVENT DESCRIPTION

6. LER NUMBER I

SEQUENTIAL I NUMBER 002 REV NO..

00

3. PAGE 2

OF 3

On January 25, 2016 an automatic reactor trip occurred on Millstone Power Station Unit 3 (MPS3)

[LER 2016-001-00). Following the MPS3 reactor trip, (Mode 3, 0% power), while operators were performing feedwater isolation (FWI) actuation verification steps in ES-0.1 (Reactor Trip Response), it was identified that the 'C' feedwater isolation valve (FWIV), 3FWS*CTV41 C, did not auto-close as expected. Operators subsequently closed 3FWS*CTV41 C from the control room.

Troubleshooting on the 3FWS*CTV41 C FWIV identified that a temporary jumper, associated with a maintenance activity completed in November 2014, was inadvertently left installed. Technical Specification (TS) 3.3.2 requires two independent channels of Solid State Protection System (SSPS) be available for FWI upon an actuation signal as a result of a safety injection signal or a reactor trip coincident with low average reactor coolant temperature, TAVE* This jumper bypassed the Train 'B' of the SSPS input to isolate 3FWS*CTV41 C upon receipt of an actuation signal, rendering the channel inoperable.

The safety function to isolate feedwater was met due to redundant valves in series ('C' feed regulating valve (FRV) and the 'C' feed regulating bypass valve (FRBV)) closing and the main feed pump tripping. These valves received their actuation signal from the Train 'A' of the SSPS. These components were not affected by the installed jumper. The operators remotely closed 3FWS*CTV41 C from the control room, thus maintaining the containment isolation safety function.

This condition is reportable in accordance with 10 CFR 50. 73 (a)(2)(i)(B) as any operation or condition that is prohibited by the plant's TS.

2. CAUSE

This was a human performance error that occurred during refueling outage 3R16 as part of a plant modification (completed in November 2014) which replaced all four Unit 3 FWIV actuators. Site personnel failed to follow the requirements of the work control process and station procedures when installing and removing the temporary jumper in the feedwater control circuit for 3FWS*CTV41 C.

3. ASSESSMENT OF SAFETY CONSEQUENCES

The main feedwater isolation function prevents steam generator overfill following steam generator tube rupture and excess feedwater events and is also credited with mitigating excess cooldown following steam line break events. Isolation of main feedwater is also credited in containment response analyses, limiting mass and energy releases to the containment for inside containment secondary pipe breaks.

The feedwater isolation function can be accomplished by closing the FWIVs or the FRVs and FRBVs, which occurs automatically following a safety injection signal or reactor trip coincident with low

, the NRG may not conduct or sponsor, and a person is not required to respond to, the information collection.

6. LER NUMBER
3. PAGE YEAR I SEQUENTIAL I REV NUMBER NO.

3 OF 3

2016 002 -

00 average reactor coolant temperature, TAVE* In addition, the main feedwater pumps are automatically tripped following a safety injection signal or a reactor trip.

While being able to fulfill the safety function, the diverse methods of isolating main feedwater would not act as rapidly as closure of the main feedwater isolation valves. There is margin between the safety analysis results Final Safety Analysis Report (FSAR Chapter 15) and containment analysis results (FSAR Chapter 6) and the ultimate event acceptance criteria of the events to accommodate the slightly longer isolation function.

With three redundant methods capable of isolating/stopping main feedwater flow, the unavailability of one individual method (i.e., the automatic closure of 'C' FWIV) results in an insignificant increase in the likelihood of failing the safety function. Consequently, the safety significance associated with exceeding the 'C' FWIV TS allowed outage time is very low.

4. CORRECTIVE ACTION

The jumper was removed and the appropriate surveillance for FWIV 3FWS*CTV41 C was performed and completed satisfactorily, verifying the valve is OPERABLE. Other feedwater system components were inspected and no additional installed jumpers were identified. Workers involved were coached concerning the need for compliance with work control procedures and standards. This event will be used as operating experience (OE) for activities associated with installation and removal of jumpers.

5. PREVIOUS OCCURRENCES

There are no previous occurrences with the same underlying reason or consequences.

6. ENERGY INDUSTRY IDENTIFICATION SYSTEM (EllS) CODES:
  • Containment-NH
  • Isolation Valve - ISV
  • Pump-P
  • Solid State Protection System -JG
  • Steam Generator-SG

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