05000254/LER-2004-001
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| 2542004001R00 - NRC Website | |
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) (If more space is required, use additional copies of NRC Form 366A)(17)
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor, 2957 Megawatts Thermal Rated Core Power Energy Industry Identification System (EIIS) codes are identified in the text as [XX] .
EVENT IDENTIFICATION
Technical Specifications Allowable Value Exceeded for Main Steam Flow Switches due to Inadequate Drift Allowance
A. CONDITION PRIOR TO EVENT
� Unit: 1 Event Date: July 13, 2004�Event Time: 1252 hours0.0145 days <br />0.348 hours <br />0.00207 weeks <br />4.76386e-4 months <br /> � Reactor Mode: 1 Mode Name: Power Operation Power Level: 085% Power Operation (1) - Mode switch in the RUN position with normal operating temperature and pressure.
B. DESCRIPTION OF EVENT
On July 13, 2004, during performance of the Unit 1 Main Steam Line (MSL) High Flow Switch Calibration and Functional Test, two main steam [SB] flow instruments [FS] were determined to have as-found setpoints that exceeded the Technical Specifications (TS) Allowable Value. The instruments were re-calibrated to be within the TS allowable range. A total of 16 switches, four per steam line, are installed on the Unit 1 MSLs. The switches feed into the Primary Containment Isolation System [JM], with a "one out of two twice" logic.
C. CAUSE OF EVENT
The root cause of this event is that inadequate drift allowance was used in the engineering setpoint calculations for the MSL flow switches in this application. The drift data assumed in the calculation was limited and did not bound actual instrument performance.
A programmatic issue was also identified. The instrument trending program did not provide timely feedback to identify potential instrument performance issues.
D. SAFETY ANALYSIS
The safety significance of this event was minimal. Although two MSL instruments were found to have setpoints outside the TS Allowable Value, there is reasonable assurance the instruments would have provided their safety function due to the considerable margin between the as-found setpoints and the Analytical Limit assumed in the plant safety analysis. This event is being reported as operation prohibited by TS due to the fact that multiple instruments were found out of calibration during the same surveillance, providing sufficient evidence that the situation existed longer than allowed by TS.
FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) Quad Cities Nuclear Power Station Unit 1 05000254 NUMBER NUMBER (If more space is required, use additional copies of NRC Form 366A)(17) E.C CORRECTIVE ACTIONS
Immediate Actions:
Prior to returning the MSL instruments to service, TS compliance was restored by re-calibrating the instruments to within the setpoint tolerance allowed by procedure.
Corrective Actions to be Completed:
A revised drift analysis for the Ul and U2 MSL flow switches will be performed using additional as-found calibration data. The current Allowable Value, Setpoint, Setting Tolerance, Expanded Tolerance and calibration frequency will be reviewed and revised as appropriate to improve margin to the Technical Specifications Allowable Value. As an interim measure, the MSL instrument calibration frequency will be increased from bi-Monthly to Monthly until the setpoint analyses and reviews described above are completed and implemented.
The instrument trending process will be enhanced to ensure a timely review of drift data to identify potential instrument performance issues.
F. PREVIOUS OCCURRENCES
Switches due to Inadequate Drift Allowance used in Setpoint Calculation," documented a previous instance of two MSL flow switches being found outside of TS Allowable Value. That instance was also attributed to the use of inadequate drift allowance in the engineering setpoint calculations. Because the MSL flow switches were newly installed at the time the setpoint calculations were performed, there was no historical drift data available. Therefore, setpoint allowances were determined using uncertainty values provided by the manufacturer along with an assumed drift term in accordance with procedural guidance. Based on the historical data that became available, the drift that was experienced exceeded the values assumed. New calibration uncertainty values were developed in response to this event. Further drift data has shown that the calibration uncertainty values developed in response to LER 2-03-005 were also inadequate. As noted above, a revised drift analysis for the Ul and U2 MSL flow switches will be performed utilizing additional historical drift data.
As indicated in LER 2-03-005, the Unit 1 and Unit 2 Barton MSL flow switches are scheduled to be replaced with differential pressure transmitters during the next refueling outages.
G. COMPONENT FAILURE DATA
The MSL flow switches are Barton Model 288A Differential Pressure Indicating Switches, with a setting range of 0 to 400 psid.