05000382/LER-2008-003
| Docket Number | |
| Event date: | 05-18-2008 |
|---|---|
| Report date: | 07-17-2008 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3822008003R00 - NRC Website | |
REPORTABLE OCCURRENCE
On May 18, 2008 at about 1621 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.167905e-4 months <br />, during refueling operations, the refueling machine computer became nonfunctional. Fuel assembly LAY405 was grappled and suspended in the core at about elevation 330 inches, near core location N-18 and other loaded fuel assemblies. Fuel assembly LAY405 was moved away from core location N-18 into clear water by placing the refueling machine in key override mode. The clear water move was a lateral move about 4 inches in the northern direction and then about 4 inches in the easterly direction. At approximately 1659 hours0.0192 days <br />0.461 hours <br />0.00274 weeks <br />6.312495e-4 months <br />, refueling personnel then raised fuel assembly LAY405 in key override mode: Technical Specification 3.9.6 requires that the refueling machine have an overload cut off limit of less than or equal to 3350 pounds for the fuel mast during the movement of fuel assemblies within the reactor pressure vessel. Technical Specification 3.9.6 ACTION 'a.' states that, "With the above requirements for the fuel mast not satisfied, suspend use of the fuel mast from operations involving the movement of fuel assemblies." The refuel team raised the fuel assembly from within the core using key override mode.
Members of the refuel team involved in raising the fuel assembly incorrectly believed that the automatic overload cut off was enabled while using key override mode, so the control room was not contacted and Technical Specification 3.9.6 was not entered. Therefore, this condition is being submitted as a violation of Technical Specification 3.9.6, reportable within 60 days pursuant to 10CFR 50.73(a)(2)(i)(B).
INITIAL CONDITIONS
At the time of discovery, the plant was in Mode 6 in the process of refueling the reactor. There were no other structures, systems, or components inoperable at the time of discovery that contributed to the condition.
EVENT DESCRIPTION
On May 18, 2008 at about 1530 hours0.0177 days <br />0.425 hours <br />0.00253 weeks <br />5.82165e-4 months <br />, fuel assembly LAY405 was moved from spent fuel pool location WW32 to the reactor core with the objective to set fuel assembly LAY405 in core location N-18. Fuel assembly LAY405 was indexed to core location N-18 and positioned for a clear water move. The attempt to move and lower fuel assembly LAY405 into core location N-18 was not successful due to an adjacent fuel assembly being off of the engagement pins. The refueling machine [FHM] computer [CPU] then became nonfunctional at about 1621 hours0.0188 days <br />0.45 hours <br />0.00268 weeks <br />6.167905e-4 months <br />. Fuel assembly LAY405 was moved away from core location N-18 into clear water by placing the, refueling machine in key override mode. The clear water move was a lateral move about 4 inches in the northernly direction and then about 4 inches in the easterly direction. At approximately 1659 hours0.0192 days <br />0.461 hours <br />0.00274 weeks <br />6.312495e-4 months <br />, refueling personnel, after ensuring that the fuel assembly was not in contact with other fuel assemblies or other reactor internals, raised fuel assembly LAY405 in order to reboot the nonfunctional computer. Technical Specification 3.9.6 was not entered prior to raising fuel assembly LAY405 without the automatic overload cut off enabled.
CAUSAL FACTORS
The Apparent Cause established that personnel failed to comply with procedure RF-005-002. Procedure RF-005-002 Rev. 302 requires entering the LCO for Technical Specification 3.9.6 when using the manual handwheel or key override to move the refueling machine hoist in an outward direction with the attached fuel assembly in the core region. Personnel did not follow procedural cautions in RF-005-002 and contact the control room for entering Technical Specification 3.9.6 prior to raising fuel assembly LAY405 in key override mode. Personnel performed in a skill based mode rather than rule based mode, thus not ensuring that there was adherence with procedure RF-005-002.
CORRECTIVE ACTIONS
The following corrective actions have been taken (Reference Condition Reports CR-WF3-2008-02427 and CR-WF3-2008-02423):
A Human Performance Evaluation Review was performed and personnel counseled on the importance of verifying procedure compliance.
An Apparent Cause Evaluation was performed.
SAFETY SIGNIFICANCE
The condition described in this LER had minimal safety significance.
The Bases for Technical Specification 3.9.6 state that the requirements for the refueling machine ensure that:
(1) the refueling machine will be used for the movement of fuel assembles, (2) each hoist has sufficient load capacity to lift a fuel assembly, and (3) core internals and pressure vessel are protected from excessive lifting forces in the event they are inadvertently engaged during lifting operations. These conditions were met during the lifting of fuel assembly LAY405 in the key override mode. There was no unintended interaction with the pressure vessel or core internals. The Technical Specification 3.9.6 overload cut off limit of 3350 pounds for the fuel mast was not exceeded while raising the fuel assembly.
Although the reported condition could have hypothetically increased the risk of damage to fuel assembly LAY405 or an adjacent fuel assembly, or involved some small risk of a fuel handling accident, this risk was minimized by the action of Waterford 3 refueling staff to move the assembly away from other assemblies into the open water area of the core before raising the assembly. There is, however, no conceivable way in which this event could have led to the severe core damage that is the end state of concern in a core damage risk assessment. Therefore, the core damage risk impact was zero.
SIMILAR EVENTS
A record search was performed for other similar reported events at Waterford 3. No similar events were identified as reported over the last 3 refueling outages.
ADDITIONAL INFORMATION
Energy, industry identification system (EIIS) codes are identified in the text within brackets [ ].