05000454/LER-2002-002
| Byron Station, Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| 4542002002R00 - NRC Website | |
A. Plant Conditions Prior to Event:
Event Date / Time: March 18, 2002 / 1516 hours0.0175 days <br />0.421 hours <br />0.00251 weeks <br />5.76838e-4 months <br /> Unit 1 — Mode 6 — Refueling, Reactor Power — 000% Reactor Coolant System [AB]: Ambient Temperature and Depressurized No structures, systems or components were inoperable at the start of the event that contributed to the event.
B. Description of Event:
Technical Specification (TS) 3.4.10, "Pressurizer Safety Valves" require three pressurizer [AB] (RY) safety valves to be operable with lift settings greater than or equal to 2460 psig and less than or equal to 2510 psig. This lift setting span is based on plus or minus 1% tolerance of a nominal 2485 psig setpoint.
Surveillance Requirement 3.4.10.1 requires each pressurizer safety valve to be lift tested in accordance with the Inservice Testing (1ST) program. The acceptance criteria of the IST lift test is for the safety valve to lift within the plus or minus 1% tolerance. Expanding the scope of testing is required when a valve's "as-found" test exceeds 3%. The IST program essentially requires one safety valve to be tested each refuel outage. Byron Station methodology for testing is to remove the safety valve and replace it with an operable valve and then send the removed valve to a testing vendor.
As part of the recent Unit 1 refuel outage (i.e., B1R11) activities, pressurizer safety valve, 1RY8010B, was removed and sent to the vendor for testing as required by the IST program. In addition, another safety valve, 1RY8010A, was removed and sent for repairs because it had minor seat leakage while on-line. The IST program requires that safety valves, which have been removed for maintenance, must also be lift-tested.
The 1RY8010B valve's as-found lift setting was +1.1% and the 1RY8010A valve was +2.0%. The valve Vendor reported this information to the Station's Inservice Testing Engineer who entered this condition into the station's corrective action program.
Since both the 1RY8010B and 1RY8010A were replaced with operable valves, no TS action condition applied at the time. However, the condition of multiple pressurizer safety valves 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 plants Technical Specifications.
K:BYR_DOCS/_LERs/20021ers/454-2002-002-00.doc licensing process and fed back to industry. Forward comments regarding burden 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 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)
C. Cause of Event:
The safety valves were inspected by the vendor and no material condition issues were found that may have contributed to the out of tolerance condition.
An Electric Power Research Institute (EPRI) evaluation concerning safety and relief valve testing, concludes these valves are performing within their design capabilities. These setpoint lift test failures are principally driven by the close tolerance between TS requirements and the actual ability of the valve to perform within the required acceptance band.
The Vendor also indicated that, based on industry experience, these valves performed normally. The vendor stated that the number of valves exceeding the 1% tolerance is significant. The Vendor indicated that most valves tested exceed the 1% level. However, most lift tests do not exceed the 2% level, and it is rare for valves to exceed the 3% range. A historical review of lift tests at Byron indicated the safety valves' performance have been consistent with this industry experience. Station Management has not been responsive in the reconciliation of the tolerance capability of these pressurizer safety valves with the Technical Specification requirements.
D. Safety Analysis:
The pressurizer safety valves provide, in conjunction with the Reactor Protection System, overpressure protection for the RCS. The safety valves are designed to prevent system pressure from exceeding the RCS safety limit of 2735 psig.
An engineering evaluation has performed an analysis on the effects of these valves lifting at the as- found setpoints. Their determination is that all acceptance criteria in the Updated Final Safety Analysis Report Chapter 15 analyses are still met.
K:BYR_DOCS/ LERs/2002Iers/454-2002-002-00.doc licensing process and fed back to industry. Forward comments regarding burden 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 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)
E. Corrective Actions:
A relaxation to the Technical Specification lift tolerance for pressurizer safety valves will be pursued.
F. � Previous Occurrences:
A review of 22 recent Byron and Braidwood Station's pressurizer safety valve lift tests indicate 12 tests were outside the 1% tolerance with seven failing high and five failing low. The average deviation of these tests was 0.22%.
G. Component Failure Data:
Manufacturer � Nomenclature � Model Number Crosby � Pressurizer Safety Valve � HB-BP-86 K:BYR_DOCS/ LERs/20021ers/454-2002-002-00.doc