05000395/LER-2009-001
| Docket Number | |
| Event date: | 08-12-2009 |
|---|---|
| Report date: | 10-12-2009 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| Initial Reporting | |
| 3952009001R00 - NRC Website | |
PLANT IDENTIFICATION
Westinghouse - Pressurized Water Reactor
EQUIPMENT IDENTIFICATION
XEG0001B-E, "B" Emergency Diesel Generator
IDENTIFICATION OF EVENT
On August 12, 2009 Surveillance Test Procedure STP-125.009 was being performed to demonstrate the capability of the "B" Emergency Diesel Generator (EDG) to start, load and operate continuously for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> per Technical Specification (TS) 4.8.1.1.2.g.7. The TS surveillance requires that during this 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> run the EDG be loaded to a target value of 4676 kilowatts (kW) (between 4600-4700 kW) and maintained for two hours. When the "B" EDG load was increased for this two hour run, the load could not be increased above an average value of 4575 kW. An adjustment was then made to Increase the fuel rack stop and the surveillance was completed satisfactorily. Since the two hour loading requirement could not be met and may have existed since the adjustment in 2008, this is a violation of the Limiting Condition for Operation for TS 3.8.1.1 and is a reportable event under 10CFR 50.73(a)(2)(i)(B).
EVENT DATE
August 12, 2009 Condition Report CR-09-03120 was initiated to address this event.
REPORT DATE
October 12, 2009
CONDITIONS PRIOR TO EVENT
Mode 1, 100% Power
DESCRIPTION OF EVENT
Surveillance testing is performed every 18 months on the EDGs to verify their load carrying capability over a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period at 100% full continuous rating for 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> and at approximately 110% load rating for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. During this surveillance test for the "B" EDG on August 12, 2009, the 110% load rating which relates to the TS range of 4600-4700 kW could not be achieved. The fuel rack stop was set too low to allow sufficient travel of the fuel rack to achieve the required load range. The fuel rack stop had previously been set on March 30, 2008 during performance of Mechanical Maintenance Procedure MMP-180.033. It was erroneously believed at the completion of this maintenance that the "as left" fuel rack stop setting resulted in loading to 4690 kW.
CAUSE OF EVENT
A root cause analysis of the event has been completed. The result of this analysis determined that the root cause was due to the fuel rack stop being set too low because of inadequate procedural guidance. Mechanical Maintenance Procedure MMP-180.033 which is used for both the "A" and "B" EDGs did not require the use of a one minute average load indication when setting the fuel rack stop. An instantaneous indication on the control room recorder IYR1804 was used to set the stop, but it did not account for load variations when the EDG is tied to the grid. The recorder can perform one minute averaging of the load signal to account for grid fluctuations, but this was not required by the procedure. In addition, the maintenance procedure did not have a target value for setting the fuel rack stop and had a non-conservative allowable load range. These procedural inadequacies resulted in the fuel rack stop being set too low.
�NRC FORM 366A (9-2007) PRINTED ON RECYCLED PAPER
ANALYSIS OF EVENT
The "A" and "B" EDGs are designed as independent trains to provide emergency power to the 7200 Volt buses in the event of loss of offsite power (LOOP). During this event on August 12, 2009, the "B" EDG was producing 4575 kW as monitored on the control room recorder IYR1804 using a one minute and ten minute average. However, this was below the TS 110% minimum loading of 4600 kW which is required for the two hour portion of the surveillance test. The design basis largest short term load (less than two hours) on the "B" EDG is 4348.7 kW, excluding optional loads, during the injection phase of a Loss of Coolant Accident (LOCA).
The "B" EDG would have been capable of supplying 100 percent of the Engineered Safety Features (ESF) loads. Therefore, the "B" EDG would have been capable of performing its design basis function.
CORRECTIVE ACTIONS
Mechanical Maintenance Procedure MMP-180.033 has been revised to require the use of a 1 minute load averaging with the main control room recorder, include a load target value and provide a more conservative load range for setting the fuel rack stop. A followup action has been initiated to include these procedure changes into the Procedure/Commitment Accountability Program (PCAP) to identify that these changes were made as a result of this event to preclude an unintentional removal of these changes from the procedure in the future.
PRIOR OCCURRENCES
On August 4, 2005 a similar event occurred with the "A" EDG during the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> surveillance test where the load could not be raised high enough to reach the TS load range of 4600-4700 kW during the required two hour maximum load period. A fuel rack stop adjustment was made in accordance with Mechanical Maintenance Procedure MMP-180.033, and a one minute average on the control room recorder was used to set the maximum loading. The maximum loading that was achieved after the adjustment was within the TS load range of 4600-4700 kW.* Although this loading met the TS required load range after the adjustment, it did not meet the target value and was not in the fuel rack stop range specified in Mechanical Maintenance Procedure MMP-180.033. Since the procedure requirements could not be met, an engineering evaluation was performed. This evaluation established a new lower acceptable range to set the fuel rack stop to meet the TS acceptance criteria. MMP-180.033 was then changed to incorporate the new fuel rack stop lower range. The procedure change also removed the target value and the previous fuel rack stop range. The cause evaluation for this August 2005 event referred to using a one minute load averaging on the control room recorder for setting the fuel rack stop. The recorder defaults to instantaneous readout and a one minute average must be selected at the start of each test. However, this was not understood. As a result, no procedure guidance was provided to select one minute averaging for the test.
In retrospect, the actions taken to resolve this prior occurrence contributed to the procedure deficiencies identified in the root cause for this LER event.
- This event may have also been reportable pursuant to 10CFR50.73(a)(2)(i)(B). This potential reportability was discovered during research for this LER and has been entered into the station's corrective action program.
_NRC FORM 366A (9-2007) PRINTED ON RECYCLED PAPER