05000298/LER-2006-001, Re Reheat Valve Failure to Re-Open Due to Contaminated Control Fluid Results in Manual Scram
| ML061210014 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 04/25/2006 |
| From: | Minahan S Nebraska Public Power District (NPPD) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NLS2006034 LER 06-001-00 | |
| Download: ML061210014 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| 2982006001R00 - NRC Website | |
text
N Nebraska Public Power District Always there when you need us NLS2006034 April 25, 2006 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Licensee Event Report No. 2006-001-00 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
/js Enclosure cc:
Regional Administrator w/enclosure USNRC - Region IV Cooper Project Manager w/enclosure USNRC - NRR Project Directorate IV-1 Senicr Resident Inspector w/enclosure USNRC - CNS NPG Distribution w/enclosure INPO Records Center w/enclosure SORC Administrator w/enclosure SRAB3 Administrator w/enclosure CNS Records w/enclosure COOPERNUCLEARSTATION P.O. Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-3811 / Fax: (402) 825-5211 21 2*
r www.nppd.com V
- FTACHMENT 3 LIST OF REGULATORY COMMITMENTSO l
Corresp :ndence Number:
NLS2006034 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
4
+
I 4-4 4-4-
1-
+
4 4
PROCEDURE 0.42 l
REVISION 19 l
PAGE 20 OF27
Abstract
On Febrjary 26, 2006, at 0250 Central Standard Time, Reheat Valve 1B 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. All control rods fully inserted and a Primary Containment Isolation System Group 2 isolation occurrec. 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. Feed and bleed actions to reduce the contamination did not eliminate particulate contamination in normally stagnant lines associated with the reheat/intercept test solenoid valves resulting in a stuck reheat valve.
Immediate actions were to cycle all intercept and reheat stop valves via the test solenoids several times to verify flushing of the electro-hydraulic fluid through the valves. Corrective actions to prevent recurrence include replacing the test solenoid valves for the turbine reheatintercept and main stop valves and flushing and replacing the electro-hydraulic fluid in the turbine generator control system.
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CORRECTIVE ACTION
The following corrective actions have been completed:
- 1. The intercept and reheat stop valves were cycled via the test solenoids. The test solenoid valves were stroked at least four times, and each time were held open for at least five seconds to verify flushing of DEH fluid through the valve.
- 2. The solenoid valves for main turbine 103% over-speed protection were stroked and remained open for at least one minute to verify complete flushing of DEH fluid through the valves.
The following corrective action will be taken:
- 1. Refozus the organization on pre-job brief activities to specify when re-performance of a pre-job brief is required, such as after a significant delay in a job, when new information is discovered about a job, when plant conditions have changed that affect a job or when new personnel become involved in a job. Due May 15, 2006.
In addition, the following corrective actions will be taken during the Cycle 23 refueling outage.
- 1. Repl 3ce the test solenoid valves for the turbine reheat/intercept and main stop valves.
- 2. Repl hce the servo valves for the turbine governor and bypass valves.
- 3. Repl.ce the electro-hydraulic fluid in the turbine generator fluid system.
- 4. Perform a flush of the turbine generator fluid system.
- 5. Repl.ace the emergency trip solenoid valves.
PREVIOUS EVENTS A review of CNS LERs since 2000 was conducted. There were no reportable events similar to this event concerning a high level alarm in a moisture separator concurrent with a reheat/intercept valve failing to re-open resulting in a manual scram. There have been no significant problems due to the cleanliness of the DEH fluid in the turbine control system prior to this event. There have been no incidents of reheat or intercept valves sticking.
NRC FORM 366 11-2001)