05000483/LER-2014-003-01, Regarding Inverter NN11 Inadvertantly Transferred to Its Alternate AC Source
| ML15064A072 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 03/05/2015 |
| From: | Bradley G Ameren Missouri, Union Electric Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| ULNRC-06181 LER 14-003-01 | |
| Download: ML15064A072 (10) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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 |
| 4832014003R01 - NRC Website | |
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'WAmeren MISSOURI Callaway Plant March 05, 2015 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 ULNRC-06181 10 CFR 50.73(a)(2)(i)(B)
Ladies and Gentlemen:
DOCKET NUMBER 50-483 CALLA WAY PLANT UNIT 1 UNION ELECTRIC CO.
FACILITY OPERATING LICENSE NPF-30 LICENSEE EVENT REPORT 2014-003-01 INVERTER NNll IN ADVERT ANTLY TRANSFERRED TOITSALTERNATEACSOURCE On August 7, 2014, Union Electric d/b/a Ameren Missouri submitted Licensee Event Report (LER) 2014-003-00 for Callaway Plant in accordance with 10 CFR 50.73(a)(2)(i)(B). LER 2014-003-00 was submitted to report a condition prohibited by Technical Specifications due to the inoperability of 120-volt vital AC instrument system power inverter NN11 for a period of time longer than that allowed by Technical Specification 3.8.7. Other Technical Specifications were affected and are identified in the LER.
As indicated in the LER submittal last August, a supplement report was expected to be submitted (as indicated per NRC Form 366, Item 14, for the LER). The enclosed supplemental LER, 2014-003-01, is hereby submitted to update the causes and corrective actions for the identified condition.
This letter does not contain new commitments.
Enclosed: LER 2014-003-01 Gregory Bradley Director Engineering Systems PO Box 620 Fulton, MD 65251 AmerenMissouri.com STARS
- Alliance
ULNRC-06181 March 05, 2015 Page 2 cc:
Mr. Marc L. Dapas Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 Senior Resident Inspector Callaway Resident Office U.S. Nuclear Regulatory Commission 8201 NRC Road Steedman, MO 65077 Mr. Fred Lyon Project Manager, Callaway Plant Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Mail Stop O-8B1 Washington, DC 20555-2738
ULNRC-06181 March 05, 2015 Page 3 Index and send hardcopy to QA File A160.0761 Hardcopy:
Certrec Corporation 4150 International Plaza Suite 820 Fort Worth, TX 76109 (Certrec receives ALL attachments as long as they are non-safeguards and may be publicly disclosed.)
Electronic distribution for the following can be made via LER ULNRC Distribution:
F. M. Diya D. W. Neterer L. H. Graessle B. L. Cox S. A. Maglio T. B. Elwood J. W. Hiller J. B. Little M. D. Hudson D. S. Turley T. G. Fugate M. A. Killebrew N. J. Fisher G. J. Reinhard G. L. Bradley Corporate Oversight Corporate Communications NSRB Secretary Performance Improvement Coordinator Resident Inspectors (NRC)
STARS Regulatory Affairs Mr. John O'Neill (Pillsbury Winthrop Shaw Pittman LLP)
Missouri Public Service Commission
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (01-2014)
LICENSEE EVENT REPORT (LER)
(See reverse 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 Callaway Plant Unit 1
- 2. DOCKET NUMBER 05000483
- 3. PAGE 1 OF 7
- 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 06 09 2014 2014 - 003 - 01 03 05 2015 FACILITY NAME DOCKET NUMBER
- 9. OPERATING MODE 1
- 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 plants Technical Specifications.
The Technical Specifications affected by the past inoperability of the various components due to the degraded electrical termination at the noted disconnect switch are identified in Section 3 of this LER.
The allowed out-of-service times (i.e., Completion Times) specified in the Required Actions of the affected Technical Specifications are also identified or discussed. For the inoperable NN11 inverter, an allowed out-of service time of 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> is specified in the TS 3.8.7. For some of the instrument channels made inoperable by the identified condition (as previously explained), allowed out-of-service times on the order of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> apply, under TS 3.3.1 and TS 3.3.2.
Since the degraded terminal connection has been presumed to exist since 2008, the resultant past inoperability of the various affected instruments/components (including the NN11 inverter itself) must be presumed to have existed for a period of time that exceeds the allowed out-of-service times permitted by the Technical Specifications. The condition must thus be reported as an operation or condition prohibited by the plants Technical Specifications.
- 6.
CAUSE OF THE EVENT
The direct cause of the event/condition is attributed to inadequate thread engagement of the screw that secures disconnect switch NN01-11 to the NN01 bus. This loose termination contributed to an interruption in power to the circuit load (SB038) when personnel accessed this disconnect switch compartment for thermography inspections and clamp-on ammeter readings on 06/09/14.
- 7.
CORRECTIVE ACTIONS
Corrective actions include enhancements to job planning aids. Specifically, location planning notes will be added to specify that verification of proper alignment and thread engagement of the screw securing the switch to the bus bar is performed.
In addition, the bus maintenance procedure will be revised to include back panel verification for proper switch alignment / thread engagement for bus bar termination screws that have been disturbed during bus cleaning / inspection activities.
- 8.
PREVIOUS SIMILAR EVENTS
Although there have been previous instances of inverters spuriously transferring to their alternate source at Callaway, there have not been previous cases of inverter failure at Callaway that were found to have been caused by a degraded (inadequate thread engagement) bus mounting screw.
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET