05000298/LER-2009-004, Regarding Manual Reactor Scram for Digital Electro-Hydraulic Fluid Leak
| ML100130214 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 01/08/2010 |
| From: | Dori Willis Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2010003 LER 09-004-00 | |
| Download: ML100130214 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| 2982009004R00 - NRC Website | |
text
N Nebraska Public Power District "Always there when you need us" NLS2010003 January 8, 2010 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Licensee Event Report No. 2009-004-00 Cooper Nuclear Station, Docket No. 50-298, DPR-46
Dear Sir or Madam:
The purpose of this correspondence is to forward Licensee Event Report 2009-004-00.
Demetrius L. Willis r V
General Manager of Plant Operations
/bk Attachment cc:
Regional Administrator w/attachment USNRC - Region IV Cooper Project Manager w/attachment USNRC - NRR Project Directorate IV-1 Senior Resident Inspector w/attachment USNRC - CNS SRAB Administrator w/attachment NPG Distribution w/attachment INPO Records Center w/attachment SORC Chairman w/attachment CNS Records w/attachment COOPER NUCLEAR STATION P.O. Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-3877 / Fax: (402) 825-5271 w nppd corn
Abstract
On November 11, 2009, at 17:43 Central Standard Time, Cooper Nuclear Station (CNS) control room operators inserted a manual reactor scram after a non-isolable digital electro-hydraulic (DEH) fluid leak developed. This was the same governor valve (GV) and fitting location that had leaked November 6, 2009, and required a forced plant shutdown. After the scram, all control rods inserted and automatic systems responded as expected.
Inspection of the governor valve fitting found that the face O-ring installed five days earlier was not the Correct size for the application and did not seal appropriately. This O-ring was acquired from a turbine generator tool box and was not added to the work order to document its use.
CNS maintenance replaced the O-rings on all electro-hydraulic fittings for GVs with new ones from warehouse inventory.
The root causes were a failure to follow the material control and warehouse issuing processes and ineffective management of the initial repair to the DEH fluid leak five days prior. CNS will use management processes to reinforce expectations for procedure compliance and will implement case study training on this event. CNS will also inventory the turbine generator tool box and remove any materials that are not in compliance with the procedure for in-process material control.
This event was not risk significant.
NRC FORM 366 (9-2007)
(If more space is required, use additional copies of (if more space is required, use additional copies of (If more space is required, use additional copies of Form 366A)
CAUSE
The root cause was a violation of the in-process material control and warehouse issuing processes. This resulted in the wrong O-ring being installed on the face of the fitting which did not allow the fitting to seal as designed. Additionally, management failed to take ownership of, and manage the response to repair the November 6, 2009, DEH fluid leak when it became known that it would require more than a maintenance activity to resolve it.
CORRECTIVE ACTION
CNS will use management processes to reinforce expectations for compliance with site procedures and will develop and implement case study training on this event for management, maintenance, engineering, and outage organization personnel.
CNS Will also inventory the turbine generator tool box and remove any materials that are not in compliance with the procedure for in-process material control.
PREVIOUS EVENTS As noted in the Event Description, a DEH leak occurred on November 6, 2009. CNS intended to take the turbine off-line to repair the DEH leak, but not shut down the reactor. After the turbine was tripped, a low water level transient occurred and a manual reactor scram was inserted.
CNS identified that an originally installed swaged joint on the DEH supply line for GV-3 was installed crooked. Additionally, the actuator bracket for GV-3 was missing a stop bolt that normally would restrict movement of the DEH supply line in response to flow-induced vibrations.
The higher than normal vibration at low power caused the DEH swaged joint to both loosen and fracture. CNS replaced all the GV EH swaged connection joints with a modified fitting, replaced the missing stop bolt, and inspected all other bolts and brackets on all GVs.
This event was reported as Licensee Event Report 2009-002 on December 30, 2009.
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© 4 ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS@4 Correspondence Number: NLS2010003 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 I
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