05000298/LER-2008-001, Regarding Turbine Reheat Stop Valve Failure Results in Manual Scram
| ML082810400 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 10/03/2008 |
| From: | Dori Willis Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2008076 LER 08-001-00 | |
| Download: ML082810400 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| 2982008001R00 - NRC Website | |
text
N Nebraska Public Power District "Always there when you need us" NLS2008076 October 3, 2008 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Licensee Event Report No. 2008-001-00 Cooper Nuclear Station, Docket 50-298, DPR-46
Dear Sir or Madam:
The purpose of this correspondence is to forward Licensee Event Report 2008-001-00.
Sincerely, Demetrius L. Willis General Manager of Plant Operations
/em Attachment cc:
Regional Administrator w/attachment USNRC - Region IV Cooper Project Manager w/attachment USNRC - NRR Project Directorate IV-l Senior Resident Inspector w/attachment USNRC - CNS SRAB Administrator w/attachment NPG Distribution w/attachment 1NPO Records Center w/attachment SORC Administrator w/attachment CNS Records w/attachment COOPER NUCLEAR STATION p.o. Box 98 / Brownville, NE 68321-0098 A"
Telephone: (402) 825-3877 / Fax: (402) 825-5211 www nppd.com
Abstract
At 0025 Central Daylight Time (CDT) on August 9, 2008, reactor power was lowered from 85%
to 69% to perform main turbine stop valve closure and steam valve functional testing. At 0156 CDT, during the first reheat/stop valve (1A) test, while reheat/stop valve had failed to reopen, a Moisture Separator (MSR) 'C' high level alarm occurred. In accordance with the alarm procedure for MSR high level, the plant was manually scrammed. Control rods fully inserted, and a Primary Containment Isolation System Group 2 isolation occurred. Plant and mitigating system responses were as expected. Risk significance was negligible. The event was caused from a manufacturing defect that caused the reheat/stop valve test solenoid to jam. The root cause was attributed to a practice of performing reheat/stop valve testing at a power level which could result in a MSR high level condition should a reheat/stop valve test solenoid malfunction. Action was taken to prevent recurrence by deleting sections in the functional test procedure for energizing the reheat/stop valve test solenoids.
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)
- 1. Sections in the Main Turbine Stop Valve Closure and Steam Valve Functional Test procedure directing the reheat/stop valve test solenoids to be energized were deleted.
- 2. Testing of the reheat/stop valves was deferred until the next refueling outage.
- 3. A reheat/stop valve solenoid test valve that had been working in good order and removed during RE23 was provided to the valve supplier for examination as a comparison. A second reheat/stop solenoid test valve that had been rejected after post maintenance testing noted "sticking" problems in RE24 (when the reheat/stop test solenoid valves were replaced) was also provided to the valve supplier for examination. Results have not yet been received.
Long term corrective actions being tracked in the CNS corrective action program include:
- 1. Revise the frequency of the Main Turbine Stop Valve Closure and Steam Valve Functional Test procedure such that any sections involving testing of intercept and reheat/stop valves are to be executed when the plant is down-powering for a refueling outage and plant power level is 25% or less.
- 2. Working with the manufacturer, determine if there is an additional step, process, or procedure that can be done to provide assurance that reheat/stop solenoid test valves can be produced and delivered to CNS without manufacturing defect that can cause the test solenoid valve to jam in service.
PREVIOUS EVENTS LER 2006-001-00 reported a similar event, but that event was attributed to DEH fluid contamination. On February 26, 2006, at 0250 Central Standard Time, Reheat Valve 1 B did not re-open after the valve was closed during conduct of a surveillance test on the main turbine reheat/intercept valves. This occurred concurrent with a high level alarm in Moisture Separator 'D'. Per procedure, the plant was manually scrammed. Control rods fully inserted, and a PCIS Group 2 isolation occurred. Reactor power, vessel pressure and level response were as expected. The cause of the event was contamination of the electro-hydraulic fluid in the turbine control system from inadvertent introduction of waste fluid to the control system fluid reservoir on August 14, 2005. Actions were taken to replace the contaminated fluid and cycle all intercept and reheat stop valves via the test solenoids several times to verify flushing of the DEH fluid through the valves. Corrective actions to prevent recurrence included replacing the test solenoid valves for the turbine reheat/intercept and main stop valves and flushing and replacing the electro-hydraulic fluid in the turbine generator control system.
I ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS@
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS0 Correspondence Number: NLS2008076 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 4-
+
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