05000352/LER-2012-001, Regarding Three Main Steam Isolation Valves Failed Hot Closing Stroke Time Surveillance Test

Regarding Three Main Steam Isolation Valves Failed Hot Closing Stroke Time Surveillance Test

ML12111A016
Person / Time
Site:	Limerick
Issue date:	04/19/2012
From:	Kearney F Exelon Generation Co, Exelon Nuclear
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
LER 12-001-00
Download: ML12111A016 (5)

LER-2012-001, Regarding Three Main Steam Isolation Valves Failed Hot Closing Stroke Time Surveillance Test

Event date:
Report date:
Reporting criterion:	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) 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
3522012001R00 - NRC Website

text

10CFR50.73 April 19, 2012 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Unit 1 Facility Operating License No. NPF-39 NRC Docket No. 50-352

Subject:

LER 2012-001-00, Condition Prohibited by Technical Specifications Involving Main Steam Isolation Valves Slow Closing Times This Licensee Event Report (LER) addresses a condition prohibited by Technical Specifications regarding the failure of a surveillance test on the main steam isolation valves. Three valves' as-found hot closing times exceeded the Technical Specification required closing time of less than or equal to five seconds. This event also involved a common-cause inoperability of independent trains.

This LER is being submitted pursuant to the requirements of 10CFR50.73(a)(2)(i)(B) and 10CFR50.73(a)(2)(vii).

There are no regulatory commitments contained in this letter.

If you have any questions, please contact John Hunter III at (610) 718-3400.

Respectfully, Original signed by F. A. Kearney Vice President - Limerick Generating Station Exelon Generation Company, LLC cc:

Administrator Region I, USNRC USNRC Senior Resident Inspector, LGS

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (10-2010)

LICENSEE EVENT REPORT (LER)

(See reverse for required number of digits/characters for each block)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013

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

1. FACILITY NAME Limerick Generating Station, Unit 1

2. DOCKET NUMBER 05000352

3. PAGE 1 OF 4

4. TITLE Three Main Steam Isolation Valves Failed Hot Closing Stroke Time Surveillance Test

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL NUMBER REV NO.

MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 05000 02 20 2012 2012 - 001 - 00 04 19 2012 FACILITY NAME DOCKET NUMBER 05000

9. OPERATING MODE 3

10. POWER LEVEL 0

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 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) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 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) 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 LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET UFSAR 15.6.4 Steam System Piping Break Outside Primary Containment describes the analysis of a main steam line break. The total integrated mass leaving the RPV through the steam line break is 108,785 lb; however, for the radiological consequence evaluation, a total mass of 140,000 lb is assumed. This analysis bounds the as-found MSIV closing times effect on the main steam line break accident radiological release analysis.

Cause of the Event

The apparent cause of this event was that valve stroke times were not optimized following test failures. A contributing cause was inherent inaccuracies in valve stroke timing practices. An additional contributing cause is the HV-041-1F028B MSIV pneumatic manifold is causing an extended delay time prior to valve motion. The extended delay time effect on the valve closing time was verified to be acceptable during the final valve timing ST since the valve closed in 4.97 seconds. In addition the inboard valve (HV-041-1F022B) in this steam line closed in 4.70 seconds which is well within the 5 second requirement.

Corrective Action Completed The MSIV cold shutdown valve test was performed successfully prior to restart.

Corrective Action Planned The MSIV cold shutdown valve test (ST-6-041-202-1) will be revised to require valve stroke time adjustment if the as-found stroke time exceeds pre-established test limits. This will ensure the as-left closing times provide adequate margin to the TS limits.

The HV-041-1F028B MSIV pneumatic manifold has been scheduled for replacement in the next Unit 1 refueling outage (1R15) in spring 2014.

MSIV stroke timing method improvements for timing accuracy will be investigated, benchmarked and incorporated as necessary.

Previous Similar Occurrences There were no previous similar occurrences of multiple MSIV slow closing time ST failures in the prior three years.

Component data:

System:

Reactor Containment Component:

HV-041-1F022B Main Steam Isolation Valve Manufacturer:

A585 Weir Valves & Controls USA INC Model:

48223-706-7503