05000454/LER-2003-004
| Docket Number | |
| Event date: | |
|---|---|
| Report date: | |
| 4542003004R00 - NRC Website | |
LICENSEE EVENT REPORT (LER) estimate to the information and Records Management Branch (t-6 03), U.S.
Paperwork Reduction Project (3150-0104), Office Of Management And Budget, Washington, DC 20503. If 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.
FACILITY NAME (1) DOCKET NUMBER (2) " LER NUMBER (6) PAGE (3) Byron Station, Unit 1 STN 05000454 NUMBER NUMBER (If more space is required, use additional copies of NRC Form 366A)(17)
A. Plant Conditions Prior to Event:
Event Date/Time: September 16, 2003 / 0551 hours0.00638 days <br />0.153 hours <br />9.11045e-4 weeks <br />2.096555e-4 months <br /> Unit 1 - Mode 1— Power Operations, Reactor Power 94% Reactor Coolant System [AB]: Normal operating temperature and pressure.
No structures, systems or components were inoperable at the start of the event that contributed to the event.
B. Description of Event:
Byron Station, Unit 1 is configured with four steam generators. Each steam generator has five Main Steam Safety Valves (MSSV) [SB], which provide overpressure protection. The MSSVs are tested each cycle in accordance with the In-Service Testing (IST) program. On September 16, 2003, with Unit 1 at 94% power, the setpoint testing of the MSSVs was initiated. Specifically, the IST program requires testing a minimum of four valves (i.e., 20%) of the twenty total MSSVs on the four steam generator loops, with all 20 valves being tested at least once every five years. However, due to the test failures incurred, the testing sample was expanded to include all 20 valves. These MSSV tests verify that the actual MSSV lift settings are in accordance with Technical Specification (TS) 3.7.1, "Main Steam Safety Valves." The TS allows a 3% tolerance on the as found lift setting and requires all tested valves to be set to a 1% as left tolerance. The test determines each valve's actual lift setting using normal system pressure with assistance from a hydraulic testing device. The MSSV testing is performed in accordance with Byron Station Maintenance Procedure (BMP) 3114-15, "Main Steam Safety Valve Verification of Lift Point Using Furmanite's Trevitest Equipment." The procedure's as left acceptance criteria require two consecutive lift tests within 1% of the valve's required lift setpoint with no adjustments performed between these tests.
The MSSV tests, and any required valve adjustments, were performed on only one valve at a time.
Valves not meeting acceptance criteria were adjusted and satisfactorily tested before proceeding to the next valve.
(KZYRSOCS1 LERS12003ferst454-2003-003-00.doc) LICENSEE EVENT REPORT (LER) estimate to the Information and Records Management Branch (1-6 133), U.S.
Paperwork Reduction Project (3150-0104), Office Of Management And Budget, Washington, DC 20503.1f 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.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) Byron Station, Unit 1 STN 05000454 NUMBER NUMBER (If more space is required, use additional copies of NRC Form 366A)(17) Description of Event (cont.) The initial lift test results on two of the 20 MSSV valves exceeded the 3% TS as found tolerance limit.
The test results are as follows:
Valve TS Setpoint (psi) 3% TS Limits (psi) Initial Lift (psi) % Difference 1MS016A 1190 1160 - 1220 1143 -3.9% 1MS015D 1205 1175 - 1235 1163 -3.5% This condition of multiple MSSVs being outside of their required lift setting tolerance band is reportable in accordance with 10 CFR 50.73 (a)(2)(i)(b), "Any operation or condition prohibited by the plant's Technical Specifications.
C. Cause of Event:
The cause of the two MSSV failures is currently unknown. A root cause investigation is still in progress and a supplement to this report will be issued if a definitive cause is determined.
D. Safety Analysis:
The primary purpose of the MSSVs is to provide overpressure protection for the secondary system.
These valves also provide protection against over-pressurizing the reactor coolant pressure boundary by providing a heat sink for the removal of energy from the reactor coolant if the preferred heat sink provided by the condenser [SD] is not available. The MSSVs also serve as containment isolation valves.
An engineering evaluation was conducted to determine the effect of having two MSSVs out of tolerance on Chapter 15, "Accident Analyses," in the Updated Final Safety Analysis Report. This analysis concluded that considering the as-found MSSV setpoints, the conclusions of Chapter 15 analyses still remain valid. Therefore, the overall impact on plant safety due to the identified condition was minimal.
This condition is not a safety system functional failure.
(1(113YR_DOCS1 LERS120031ers1454-2003-003-00.doc) LICENSEE EVENT REPORT (LER) estimate to the information and Records Management Branch (t-6 f33), U.S.
Paperwork Reduction Project (3150-0104), Office Of Management And Budget, Washington, DC 20503. If an Information collection does not display a currently valid 0MB control number, the NRC may not conductor sponsor, and a person is not required to respond to. the Information collection.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) Byron Station, Unit 1 STN 05000454 NUMBER NUMBER (If more space is required, use additional copies of NRC Form 366A)(17)
E. Corrective Actions:
The Maintenance Department immediately notified Operations after each of the initial MSSV lifts that exceeded the +/-3% TS limit and the appropriate TS Action Condition was entered. The valves were adjusted and re-tested satisfactorily.
The I MS016A and IMS015D valves will be retested in the next setpoint testing campaign scheduled for Spring 2005.
F. Previous Occurrences:
During the previous four years there have been several LERs at Byron Station involving multiple MSSVs lifting outside their acceptance criteria, however these events involve the MSSVs lifting high and were attributed to the disc bonding phenomena. One previous LER was found involving multiple valves lifting low.
Testing Due to Unknown Causes," dated 4/14/003.
G. Component Failure Data:
Manufacturer � Nomenclature � Model � Mfg. Part Number Dresser � Main Steam Safety Valve (MSSV) � 3707R � N/A (K13YR_DOCS1_LERS12003Iers4454-2003-003-00.doc)