05000483/LER-2003-008
| Callaway Plant Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 4832003008R00 - NRC Website | |
1. DESCRIPTION OF THE REPORTABLE EVENT
A. REPORTABLE EVENT CLASSIFICATION
This event is reportable under 10CFR50.73(a)(2)(i)(B), an operation or condition prohibited by Technical Specifications.
B. PLANT OPERATING CONDITIONS PRIOR TO THE EVENT
Callaway was in Mode 1 at 100 percent power.
C. STATUS OF STRUCTURES, SYSTEMS OR COMPONENTS THAT WERE INOPERABLE
AT THE START OF THE EVENT AND THAT CONTRIBUTED TO THE EVENT
Not Applicable.
D. NARRATIVE SUMMARY OF THE EVENT, INCLUDING DATES AND APPROXIMATE
TIMES
On 9/4/03, with Callaway in Mode 1 at 100 percent power, a modification was implemented to install a new hand switch for BBHV8000B, `13. Pressurizer (Pzr) Power Operated Relief Valve (PORV) Block valve. This modification would have resulted in a seal-in circuit for the momentary OPEN function of the handswitch and a maintained contact circuit for the CLOSED function. Following post modification testing, an on-coming Reactor Operator noted the OPEN indication for BBHV8000B was not lit. It was determined that breaker NGO2BDF1 for BBHV8000B had tripped.
Subsequent investigation determined the thermal overload relays for NGO2BDF1 (the valve's motor operator power supply) and limit switches for BBHV8000B were damaged. The modification package required a jumper wire be removed, but was not addressed in the work instructions. Because of this oversight, the valve control circuit modification was completed with the jumper wire still installed.
With the jumper wire installed, a continuous OPEN signal for BBHV8000B resulted anytime hand switch BBHIS80008 was in the AUTO or OPEN position. The jumper wire also bypassed the open limit switch and open torque switch for the Limitorque actuator. When the valve was stroked open, stem travel was stopped by engagement of the valve's backseat while the Limitorque motor remained energized as it tried to open the valve further. The constantly energized motor overheated resulting in short-circuiting the motor windings. The increased valve stem travel also caused the valve limit switches to be damaged. Inspection of the breaker cubicle revealed damaged overload relays. The power cables were megger tested and found to be undamaged.
BBHV8000B had been declared Inoperable at 0601 on 9/4/03 to implement the hand switch modification. The associated Technical Specification 3.4.11 Required Action was to restore the valve to OPERABLE status within the Completion Time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. It was determined that repairs would require replacing the Limitorque actuator, including the motor, and restoring BBHIS8000B to the pre-modification configuration. An Operability Determination was completed for BBHV8000B which established that the valve, valve stem, and bonnet were operable until Refuel 13. During Refuel 13 the valve components will be inspected for degradation. The valve stem will be replaced.
By mid-day 9/5/03, it was recognized that repairs might not be completed within the Technical Specification 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time. The subsequent Required Action required placing the plant in Mode 3 with an associated Completion Time of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. On 9/6/03 a Notice of Enforcement Discretion (NOED) was requested to exceed the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Technical Specification Completion Time. On 9/6/03 the NRC verbally approved a NOED, granting a 48-hour extension to the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time to complete repairs and testing of the valve. As required by the NOED, compensatory measures were implemented to assure the extended Technical Specification Completion Time did not adversely impact nuclear safety.
Valve actuator replacement and control circuitry work were completed early on 9/7/03. All evaluations and operability reviews were completed and the Technical Specification Required Action plus NOED were exited at 1418, 917/03.
E. METHOD OF DISCOVERY OF EACH COMPONENT, SYSTEM FAILURE, OR
PROCEDURAL ERROR
The Reactor Operator noticed the failed light indication for BBHV8000B. Subsequent investigations identified the faulted breaker and valve operator, eventually leading to the discovery of the jumper wire inadvertently left in the control circuit.
II. � EVENT DRIVEN INFORMATION
A. SAFETY SYSTEMS THAT RESPONDED
Not Applicable for this event.
B. DURATION OF SAFETY SYSTEM INOPERABILITY
Per Technical Specification 3.4.11 Required Action C, a 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time is allowed to effect repairs and exit the Required Action. If repairs are not completed within the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Completion Time, Required Action D requires placing the plant in Mode 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. The actual time BBHV8000B was inoperable was 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />, 17 minutes. Therefore, this event represents a violation of Technical Specification 3.4.11 and is reportable per 10CFR50.73(a)(2)(i)(B) as a condition which was prohibited by Technical Specifications.
C. SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT.
Compensatory measures were implemented to assure that the NOED extended Technical Specification Completion Time did not adversely impact nuclear safety. A risk analysis performed to support the NOED request determined that the compensatory measures actually enhanced NRC FORM MA t
- 2001) safety (i.e., reduced core damage frequency). Therefore, there were no adverse safety consequences as a result of the additional time in the Action Statement as discussed in the NOED submittal.
III. CAUSE OF THE EVENT
A formal Root Cause Analysis team was assembled to review this event. The root cause of this event was determined to be lack of adequate work instructions in the modification work package.
IV. CORRECTIVE ACTIONS
Interim corrective actions restrict planning of motor operated valve control circuit work documents. Long term corrective actions include strengthening the training and qualification process for the planning of motor operated valve modification work documents.
V. PREVIOUS SIMILAR EVENTS
A search of the Callaway Action Request System (CARS) was performed to identify previous CARs related to this issue. No previous similar events were identified.
A review of LERs submitted from September, 2000 until present did not reveal any similar LERs.
VI. ADDITIONAL INFORMATION
The system and component codes listed below are from the IEEE Standard 805-1984 and IEEE Standard 803A-1984 respectively.
System: � AB Component: � ISV