05000353/LER-2008-003
| Limerick Generating Station | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3532008003R00 - NRC Website | |
Unit Conditions Prior to the Event Unit 2 was in Operational Condition (OPCON) 1 (Power Operation) at approximately 100% power. There were no structures, systems or components out of service that contributed to this event.
Description of the Event
On Tuesday April 15, 2008, Limerick Unit 2 was operating at approximately 100% power and the surveillance test coordinator (STC) was performing a review of a completed functional test on the reactor enclosure cooling water radiation monitoring system (RECW-RMS) (EIIS:CC) (EIIS:IL). The STC identified that the "as left" alarm (EIIS:RA) setpoint was documented as 1100 counts per minute (CPM), which was greater than the test "required limit" of 1050.CPM. The STC informed Operations shift management that the radiation monitor was potentially' inoperable due to the documented test data. An investigation determined that the test data was accurate and the radiation monitor was inoperable. Operations shift management declared the radiation monitor inoperable at approximately 1210 hours0.014 days <br />0.336 hours <br />0.002 weeks <br />4.60405e-4 months <br /> and directed obtaining a grab sample every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
An investigation determined that the radiation monitor was rendered inoperable on March 24, 2008, during the last performance of the functional test when the technician failed to recalibrate the alarm setpoint as required by the test.
The radiation monitor was restored to operable status on April 16, 2008, at 1030 hours0.0119 days <br />0.286 hours <br />0.0017 weeks <br />3.91915e-4 months <br />, following successful performance of the functional test. The radiation monitor was inoperable for approximately 23 days.
Technical Specification (TS) 3.3.7.1 requires one operable RECW radiation monitor channel "at all times." With the radiation monitor inoperable, Table 3.3.7.1-1 Action 72 applies. Action 72 requires obtaining and analyzing RECW grab samples every 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The required grab samples were not collected until the radiation monitor was discovered to be inoperable following the STC identification of the test performance error.
This event resulted in a condition prohibited by Technical Specifications. Therefore, this LER is being submitted pursuant to the requirements of 10CFR50.73(a)(2)(i)(B).
Analysis of the Event
There were no actual safety consequences associated with this event. The potential safety consequences of this event were minimal. The RECW-RMS Hi-Hi alarm setpoint was not within the required range but the Hi alarm setpoint was functional and would have alerted Operations of an increase in RECW radiation levels during the affected period. In addition, the RECW-RMS count rate was continuously indicated and recorded in the control room and was monitored during routine control panel walkdowns. The service water radiation monitor remained operable during the affected period.
The TS bases state that the instrument ensures that radiation levels are continually measured, the alarm is initiated when the radiation level trip setpoint is exceeded, and sufficient information is available on the plant parameter to monitor and assess the variable following an accident.
The RECW-RMS is designed to detect leakage from contaminated systems into the RECW system, which provides a barrier to release to the environment. Service water provides the cooling medium for the RECW heat exchanger and is also designed with a process radiation monitor.
The RECW-RMS is described in Limerick UFSAR, Sections 7.7.9.12 and 11.5.2.2.13. The system is classified as a non-safety related process radiation monitoring system (PRMS). The system provides an upscale/downscale trip signal to an annunciator in the control room. The system provides no control trip function. Radiation data is continuously recorded in the control room.
Cause of the Event
The condition was caused by a less than adequate self check by the technician recording the as found data during the .
functional test surveillance. In addition, the peer check and supervisory review of the test data was less than adequate.
Corrective Action Completed A work group stand-down was performed.to reinforce the consequences of not applying the barriers that are designed for error prevention.
All Instrument and Control (I&C) work group surveillance test performers perform an independent verification and initial each surveillance test data table. I&C supervisors review and initial each surveillance test data table.
Corrective Action Planned I&C surveillance test reviewer training will be performed to reinforce the critical risk elements of reviewing surveillance tests.
Previous Similar Occurrences There were no previous similar occurrences of reportable inoperability of TS equipment due to a surveillance test error in the past three years.
Component data:
Component description: Reactor Enclosure Cooling Water Radiation Monitor Component number:�RISH-013-2K606 Manufacturer: G080 General Electric Company Model number: 145C3284AAG001
References:
ST-2-013-600-2 Radiation Monitoring - Reactor Enclosure Cooling Water System Monitor Functional Test (RISH-13-2K606)