05000446/LER-2004-001
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4462004001R00 - NRC Website | |
I. DESCRIPTION OF REPORTABLE EVENT
A. REPORTABLE EVENT CLASSIFICATION
Any operation or condition prohibited by the plant's Technical Specifications.
B. PLANT OPERATING CONDITIONS PRIOR TO THE EVENT
On January 13, 2004, Comanche Peak Steam Electric Station (CPSES) Unit 2 was in Mode 1, Power Operation, operating at 99.5 percent power.
C. STATUS OF STRUCTURES, SYSTEMS, OR COMPONENTS THAT WERE
INOPERABLE AT THE START OF THE EVENT AND THAT CONTRIBUTED
TO THE EVENT
There were no inoperable structures, systems, or components that contributed to the event.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND
APPROXIMATE TIMES
On January 6, 2004, Comanche Peak Steam Electric Station (CPSES) Unit 2 was in Mode 1 operating at 99.5 percent power. At 0804 hours0.00931 days <br />0.223 hours <br />0.00133 weeks <br />3.05922e-4 months <br />, an Instrument and Control (I&C) Technician (utility, non-licensed) was performing sensor response time testing on Channel III Refueling Water Storage Tank (RWST) level transmitter 2-LT-0932 [EIIS:(BQ)(TK)(LT)]. During this test, a reference leg isolation valve [EIIS:(BQ)(LT)(ISV)] is closed and then reopened. During performance of the test the valve was closed, however, due to personnel error it was inadvertently left in the closed position after completion of the test. With the valve closed, the level transmitter was not able to properly respond to changing water level in the RWST after completion of the test.
On January 13, 2004, at 1520 hours0.0176 days <br />0.422 hours <br />0.00251 weeks <br />5.7836e-4 months <br />, while investigating an RWST low level alarm [EIIS:(BQ)(TK)(LA)], Operators (utility, licensed) in the Unit 2 Control Room discovered that the reference leg isolation valve associated with level transmitter 2-LT- 0932 was closed. RWST level channel 2-L-0932 was declared inoperable and Technical Specification 3.3.2 was entered. This Technical Specification requires that the inoperable channel be placed in bypass within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> or the affected Unit must be in Mode 3 within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. Channel 2-L-0932 was inoperable from January 6, 2004 to January 13, 2004, and this exceeded the TS completion time of 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to be in Mode 3. Therefore, a reportable condition prohibited by the Technical Specifications occurred.
E. THE METHOD OF DISCOVERY OF EACH COMPONENT OR SYSTEM
FAILURE, OR PROCEDURAL OR PERSONNEL ERROR
Channel III RWST level transmitter was closed.
II. COMPONENT OR SYSTEM FAILURES
A. FAILURE MODE, MECHANISM, AND EFFECTS OF EACH FAILED
COMPONENT
Not applicable — No component failures were identified during this event.
B. CAUSE OF EACH COMPONENT OR SYSTEM FAILURE
Not applicable — No component or system failures were identified during this event.
C. SYSTEMS OR SECONDARY FUNCTIONS THAT WERE AFFECTED BY
FAILURE OF COMPONENTS WITH MULTIPLE FUNCTIONS
Not applicable — No component failures were identified during this event.
D. FAILED COMPONENT INFORMATION
Not applicable — No component failures were identified during this event.
III. ANALYSIS OF THE EVENT
A. SAFETY SYSTEM RESPONSES THAT OCCURRED
Not applicable — No safety system responses occurred as a result of this event.
B. DURATION OF SAFETY SYSTEM TRAIN INOPERABILITY
RWST level channel 2-L-0932 was inoperable from January 6, 2004 to January 13, 2004.
NRC FORN1 366A (1-20011 Facility Name (I) COMANCHE PEAK STEAM ELECTRIC STATION UNIT 2 LER Number (6) Year � Sequential � Revision Number � Number 04 PI 001 � 00 Docket Fago(3) Enclosure to TXX-04024
C. SAFETY CONSEQUENCES AND IMPLICATIONS
The RWST level channels are necessary for initiating the semi-automatic switchover of the Emergency Core Cooling System (ECCS) suctions from the RWST to the containment sump. Four channels are available; however, because there is no automatic control function associated with these functions, only three channels are required in order to satisfy the single failure criterion and provide the required redundancy. Throughout the duration of the event, the minimum required number of channels (three) was available. Therefore, the three operable level channels would have adequately initiated the ECCS switchover, if required.
In addition, during the seven days that level channel 2-L-0932 was inoperable, no event occurred that required the automatic switchover to containment sump function. These channels are highly reliable and had an event occurred that required this function, it is highly likely that the two-out-of-four logic would have been satisfied.
There were no safety system functional failures associated with this event.
Based on the above, it is concluded that the event of January 13, 2004, did not adversely affect the safe operation of CPSES Unit 2 or the health and safety of the public.
IV. CAUSE OF THE EVENT
TXU Generation Company LP believes that the cause of the event was the failure by an I&C Technician to return an isolation valve to the correct position during the performance of sensor response time testing on an RWST level transmitter. The sensor response time test procedure contributed to the personnel error because it had not been updated to reflect changes from a recent plant modification and as a result it was missing steps related to manipulation of the reference leg isolation valve. In addition, the personnel performing the test did not meet management expectations to stop the test and restore the proper configuration when procedure problems were encountered.
V. CORRECTIVE ACTIONS
Upon discovery, the reference leg isolation valve was opened, a channel check was performed, and channel 2-L-0932 was declared operable on January 13, 2004, at 1630 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20215e-4 months <br />. The and the four RWST level channels on Unit 1 were checked and verified to be in the correct position. The eight affected response time test procedures for Units 1 and 2 were revised to include the missing steps related to manipulation of the reference leg isolation valve.
Expectations were reinforced with the I&C Technician that performed the sensor response time test.
As a part of the CPSES corrective action program, the following actions will be taken to prevent recurrence:
1. The Maintenance procedure revision process will be enhanced to aid Maintenance personnel in the identification of procedures that require revision as a result of modifications to the plant.
2. Management expectations regarding the expected response to an inadequate procedure will be reinforced with appropriate personnel.
VI. PREVIOUS SIMILAR EVENTS
There has been one other reportable event in the last three years that involved valves left in the incorrect position (see LER 446/03-003). However, the cause of that event was sufficiently different such that the previous corrective actions could not have prevented this event.