05000352/LER-2015-001, Regarding Valid Automatic Actuation of the Reactor Protection System with the Reactor Critical Due to One MSIV Closure

Regarding Valid Automatic Actuation of the Reactor Protection System with the Reactor Critical Due to One MSIV Closure

ML15114A236
Person / Time
Site:	Limerick
Issue date:	04/24/2015
From:	Dougherty T Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LG-15-054 LER 15-001-00
Download: ML15114A236 (4)

LER-2015-001, Regarding Valid Automatic Actuation of the Reactor Protection System with the Reactor Critical Due to One MSIV Closure

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation 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)(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
3522015001R00 - NRC Website

text

10CFR50.73 LG-15-054 April 24, 2015 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Unit 1 Renewed Facility Operating License No. NPF-39 NRC Docket No. 50-352

Subject:

LER 2015-001-00, Valid Automatic Actuation of the Reactor Protection System with the Reactor Critical Due to Closure of One Main Steam Isolation Valve This Licensee Event Report (LER) addresses a valid automatic actuation of the reactor protection system (RPS) when the reactor was critical. The event was due to an unexpected closure of the 1C Inboard main steam isolation valve (MSIV). The valve closed due to a fitting failure for the instrument gas supply tubing at the valve.

This LER is being submitted pursuant to the requirements of 10CFR50.73(a)(2)(iv)(A).

There are no commitments contained in this letter.

If you have any questions, please contact Robert B. Dickinson at (610) 718-3400.

Respectfully, Original signed by Thomas J. Dougherty Vice President - Limerick Exelon Generation Company, LLC cc:

Administrator Region I, USNRC USNRC Senior Resident Inspector, LGS

NRC FORM 366 (01-2014)

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (01-2014)

LICENSEE EVENT REPORT (LER)

(See Page 2 for required number of digits/characters for each block)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 01/31/2017 Estimated burden per response to comply with this mandatory collection request: 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.

Reported lessons learned are incorporated into the licensing process and fed back to industry.

Send comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by internet e-mail to Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, 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 3

4. TITLE Valid Automatic Actuation of the Reactor Protection System With the Reactor Critical Due to One MSIV Closure

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 23 2015 2015 -

001

- 00 04 24 2015 FACILITY NAME DOCKET NUMBER 05000

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 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)

10. POWER LEVEL 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 100 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

Analysis of the Event

There was no actual safety consequence associated with this event. The potential safety consequences of this event were minimal. The plant equipment performed as designed during the transient. The operators effectively stabilized reactor parameters and verified all control rods were fully inserted.

Exelon PowerLabs failure analysis determined that the fitting failed due to high cycle fatigue.

Review of the design configuration, recent modifications, and maintenance found no issues identifying inadequate tubing support or excessive system vibration.

Cause of the Event

The reactor scram was the result of a high reactor pressure condition due to the unexpected closure of the 1C I/B MSIV following the failure of a fitting on the instrument gas supply tubing to the valve. The cause of the event was that an undersized fitting was installed on the air supply tubing to the 1C I/B MSIV, which was not capable of withstanding existing cyclic stresses.

Corrective Actions Completed The 1C I/B MSIV instrument gas supply reducing port connector was replaced with a 3/8 inch port connector.

An inspection of Unit 1 I/B and O/B MSIV PCIG/Instrument Air tubing was performed to verify the correct fittings are installed as specified by the design drawings or subsequent evaluation.

The inspection found the correct fittings on the remaining Unit 1 I/B and O/B MSIVs.

Corrective Action Planned An inspection of Unit 2 I/B and O/B MSIV PCIG/Instrument Air tubing will be performed during the current refueling outage to verify the correct fittings are installed as specified by the design drawings or subsequent evaluation.

Previous Similar Occurrences There was no previous similar occurrence in the last five years of an automatic actuation of RPS due to an unexpected MSIV closure.

Component data:

System:

SB Main/Reheat Steam System Component:

ISV Valve, Isolation Component number: HV-041-1F022C-OP Manufacturer:

A585 Weir Valves & Controls USA INC.

Model number:

21150-H DWG