05000336/LER-2013-004, Unit 2 Regarding Reactor Trip While Backwashing D Waterbox

Unit 2 Regarding Reactor Trip While Backwashing D Waterbox

ML14002A314
Person / Time
Site:	Millstone
Issue date:	12/19/2013
From:	Scace S Dominion Nuclear Connecticut
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
13-656 LER 13-004-00
Download: ML14002A314 (6)

LER-2013-004, Unit 2 Regarding Reactor Trip While Backwashing D Waterbox

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 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)(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)(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)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(iv)(B), System Actuation
3362013004R00 - NRC Website

text

Dominionl Dominion Nuclear Connecticut, Inc.

Rope Ferry Rd., Waterford, CT 06385 Mailing Address: P.O. Box 128 Warerford, CT 06385 doons.co DEC 19 2013 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.

MPS Lic/LES Docket No.

License No.13-656 RO 50-336 DPR-65 DOMINION NUCLEAR CONNECTICUT. INC.

MILLSTONE POWER STATION UNIT 2 LICENSEE EVENT REPORT 2013-004-00 REACTOR TRIP WHILE BACKWASHING D WATERBOX This letter forwards Licensee Event Report (LER) 2013-004-00 documenting an event that occurred at Millstone Power Station Unit 2 on November 9, 2013. This LER is being submitted pursuant to 10 CFR 50.73(a)(2)(IV)(A).

If you have any questions or require additional information, please contact Mr. William D. Bartron at (860) 444-4301.

Sincerely,

/Stephe rE. Sca e Site Vice President - Millstone Attachments: 1 Commitments made in this letter: None

Serial No.13-656 Docket No. 50-336 Licensee Event Report 2013-004-00 Page 2 of 2 cc:

U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd, Suite 100 King of Prussia, PA 19406-2713 J. S. Kim Project Manager - Millstone Power Station U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 C2A Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station

Serial No.13-656 Docket No. 50-336 Licensee Event Report 2013-004-00 ATTACHMENT LICENSEE EVENT REPORT 2013-004-00 MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC.

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2016 (10/2010)

, the NRC may not conduct or sponsor.

digits/characters for each block) and a person is not required to respond to. the information collection.

3. PAGE Millstone Power Station - Unit 2 05000336 1 OF 3

4. TITLE Reactor Trip While Backwashing D Waterbox

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED I

FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER REV MONTH DAY YEAR 05000 FACILITY NAME DOCKET NUMBER 11 09 2013 2013-004-00 12 19 2013 05000

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

9. OPERATING MODE 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1 )(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A)

X 50.73(a)(2)(iv)(A) 50.73(a)(2)(x)

10. POWER LEVEL 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71 (a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71 (a)(5) 095 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)

OTHER 20.2203(a)(2)(vi) 50.73(a)(2)(i)(B) 50.73(a)(2)(v)(D)

Specify in Abstract below or in

1.

EVENT DESCRIPTION

On November 9, 2013, at 1514, Millstone Power Station Unit 2 (MPS2) experienced a turbine trip and an automatic reactor trip from 95% power MODE 1 due to loss of condenser vacuum.

The Unit was in the process of condenser backwashing operations in accordance with plant procedures. The loss of condenser vacuum was due to unexpected pump ramp-down of the 'C' circulating water pump (CWP) when the 'D' CWP was secured as required by procedure. This resulted in both CWPs being secured in the 'B' condenser. This caused the condenser vacuum to drop resulting in a turbine trip which immediately caused the reactor trip breakers to open. All the control rods inserted into the reactor core. Reactor coolant (RCS) and main steam systems responded as expected. There were no indications of safety valve actuation. Steam generator (SG) pressures were maintained below 920 psia. RCS temperature response was as expected post trip and returned to its nominal no-load Tcold of 532 degrees F. An auxiliary feedwater (AFW) automatic start occurred post trip, as expected and SG water level was recovered. All safety systems functioned as required.

This event is being reported per 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in a manual or automatic actuation of systems listed in 10 CFR 50.73(a)(2)(iv)(B). Actuations of the reactor protection system and the AFW system are reportable under this paragraph.

2.

CAUSE

Post trip troubleshooting revealed that the direct cause of the event was the MPS2 'C' CWP ramped off due to failure of contacts on a time-delay relay to deenergize as designed. This relay is a pump permissive relay designed to de-energize when the 'D' CWP is fully secured.

3.

ASSESSMENT OF SAFETY CONSEQUENCES

The operating crew responded to the reactor trip by completing EOP 2525, Standard Post Trip Actions, and entering EOP 2526 Reactor Trip Recovery. The AFW system started in response to low steam generator level as designed.

All control rods inserted on the reactor trip. With the 'A' and 'B' CWPs still running, condenser vacuum remained adequate for operation of the condenser dump valves following the reactor trip. Both main and auxiliary feedwater provided makeup to the SGs.

Based on the above discussion, there were no safety consequences for the event.

4. CORRECTIVE ACTION

The defective relay was replaced. Additional corrective actions are being taken in accordance with the station's corrective action program.

5.

PREVIOUS OCCURRENCES

Similar events are documented in the following LERs:

0 MPS2 LER 2010-003-00, Reactor Trip on Low Condenser Vacuum.

I

6.

Energy Industry Identification System (EIIS) codes are Circulating Water System - SG Circulating Water Pump -SG, P Main Condenser - COND Reactor Protection System - JC Reactor Trip Breakers -JC, BKR Reactor Coolant System - AB Main Steam System - SB Auxiliary Feedwater System - BA I