05000298/LER-2006-005, Regarding Residual Heat Removal Loop B Injection Valve Failure Due to Incorrect Pinion Gear Installation in Motor Operator
| ML063540166 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 12/15/2006 |
| From: | Minahan S Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2006100 LER 06-005-00 | |
| Download: ML063540166 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2982006005R00 - NRC Website | |
text
H Nebraska Public Power District Always there when you need us NLS2006100 December 15, 2006 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Licensee Event Report No. 2006-005-00 Cooper Nuclear Station, NRC Docket 50-298, DPR-46 The purpose of this correspondence is to forward a Licensee Event Report.
Sincerely, Stewart B. Minahan General Manager of Plant Operations
/dm Enclosure cc:
Regional Administrator w/enclosure USNRC - Region IV Project Manager w/enclosure USNRC - NRR Project Directorate IV-1 Senior Resident Inspector w/enclosure USNRC - CNS NPG Distribution w/enclosure INPO Records Center w/enclosure SORC Administrator w/enclosure SRAB Administrator w/enclosure CNS Records w/enclosure COOPER NUCLEAR STATION P.O. Box 98 / Brownville, NE 68327-0098 Telephone: (402) 825-3811 / Fax: (402) 825-5211 www.nppd.com
Abstract
At 04:05 CST on October 17, 2006, during surveillance testing, the Residual Heat Removal (RHR) Motor Operated Valve (MOV) Loop B injection valve (RHR-MOV-25B) failed to open when the associated switch was placed to open. Immediate action consisted of exiting the surveillance procedure and declaring the subject valve inoperable. The failure was a result of a dislocated motor pinion gear in the associated Limitorque motor operator. The MOV was incapable of opening for a period of approximately three months, which is a condition prohibited by Technical Specification 3.5.1 where one Emergency Core Cooling System train was inoperable for a period greater than seven days. The cause of the MOV failure was determined to be an improper pinion gear installation resulting from non-specific procedural guidance. This event was not risk significant.
NRC FORM 366 (6-2004)
(If more space is required, use additional copies of (If more space is required, use additional copies of Form 366A)
PLANT STATUS Cooper Nuclear Station (CNS) was at 92% power in Mode 1 at the time of the event.
BACKGROUND The safety objective of the Residual Heat Removal (RHR) system [EIIS:BO] is to provide core cooling, in conjunction with other Emergency Core Cooling Systems (ECCS), and to provide containment cooling as required during abnormal operational transients and postulated accidents. The RHR system consists of two heat exchangers [EIIS:HX], four main system pumps [EIIS:P] in two divisions, and associated piping, valves, controls and instrumentation. Upon opening the RHR Loop B injection valve (RHR-MOV-25B) [EIIS:INV,ISV] a path is provided for low pressure coolant injection (LPCI)[EIIS:BO] and shutdown cooling (SDC) to the reactor pressure vessel (RPV)[EIIS:RPV]. In the normally closed position, this valve provides a primary containment isolation function for the associated line.
EVENT DESCRIPTION
On October 17, 2006 the plant was in Mode 1, in preparation for a refueling outage. At 04:05 CST, during surveillance testing, motor operated valve (MOV) RHR-MOV-25B failed to open when the associated switch [EIIS:HS] was placed to open. Immediate action consisted of exiting the surveillance procedure and declaring the subject valve inoperable. The MOV was repaired, tested, and returned to OPERABLE status on October 18, 2006 at 05:18 CST.
BASIS FOR REPORT This event is reportable under 10CFR50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications (TS). This is based on determining that injection valve RHR-MOV-25B was incapable of opening for a period of approximately three months. This was a condition prohibited by Technical Specification 3.5.1 where one ECCS train was inoperable for a period greater than seven days. Although other MOV actuators were identified with varying degrees of degradation, only RHR-MOV-25B was determined to be incapable of performing its safety function during the period required by TS. This was not a loss of core cooling or containment safety function because the redundant RHR Loop A remained operable.
NRC FORM 366 (1-2001)(1-2001)
U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER)
- 1. FACILITY NAME Cooper Nuclear Station 17.
- 3.
MOVs determined to be "high risk" were inspected during RFO-23 for similar problems. Individual corrective actions to ensure continued operability have been completed.
The following actions are being tracked in the CNS corrective action program.
- 1.
Revise CNS procedures associated with Limitorque motor pinion gear inspection and assembly.
- 2.
Perform inspections and repairs (as necessary) of remaining extent-of-condition MOV actuators during Cycle 24 and RFO-24.
- 3.
Establish appropriate Preventive Maintenance Plans to periodically inspect Limitorque motor shaft & pinion gear interface.
PREVIOUS EVENTS There have been no recent reportable events related to MOV failures related to maintenance.
NRC FORM 366 1-2001)
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS@
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© Correspondence Number: NLS2006100 The following table identifies those actions committed to by Nebraska Public Power District (NPPD) in this document. Any other actions discussed in the submittal represent intended or planned actions by NPPD. They are described for information only. and are not regulatory
commitments
Please notify the Licensing Manager at Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.
COMMITMENT
COMMITTED DATE
COMMITMENT
NUMBER OR OUTAGE None PROCEDURE 0.42 REVISION 20 PAGE 18 OF 25