05000255/LER-2002-003
| Palisades Nuclear Plant | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2552002003R00 - NRC Website | |
EVENT DESCRIPTION
On December 21, 2002, at approximately 2355 hours0.0273 days <br />0.654 hours <br />0.00389 weeks <br />8.960775e-4 months <br />, with the plant in Mode 1, operating at 100% power, it was discovered during surveillance testing, that the pipe caps for two test taps on the right channel containment hydrogen monitor [IK] instrument lines were not installed. The open test taps would have precluded the ability of the right channel containment hydrogen monitor to obtain a representative post-accident containment atmospheric sample, rendering the right channel containment hydrogen monitor inoperable. The right channel containment hydrogen monitor is believed to have been in this condition for approximately 20 months, exceeding the 30-day completion time of Technical Specification 3.3.7.A for restoring an inoperable channel of containment hydrogen monitoring to operable status.
A review of the status of the left channel containment hydrogen monitor during the 20-month period that the right channel was inoperable revealed one occasion, in November 2002, during which the left channel was inoperable for approximately 9 days, exceeding the 72-hour completion time of Technical Specification 3.3.7.D for restoring one of two channels of containment hydrogen monitoring to operable status. All other occasions of left channel containment hydrogen monitor inoperability during the 20-month period were of durations less than the allowed 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
This occurrence is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.
Upon discovery, the test tap pipe caps were reinstalled and the right channel containment hydrogen monitor was declared operable.
CAUSE OF THE EVENT
The right channel test tap pipe caps were apparently not reinstalled during the restoration portion of the containment integrated leak rate test, occurring during the 2001 refueling outage in May 2001.
The cause of the failure to reinstall the test tap pipe caps is attributable to human performance individual failures involving inadequacies in procedure compliance, self-checking and independent verification. Contributing causes were that the subject test tap pipe caps were not labeled and not included on the system checklist.
The left channel containment hydrogen monitor was removed from service in November 2002 for maintenance and calibration under the assumption that the right channel containment hydrogen monitor was operable.
CORRECTIVE ACTIONS
Operator performance expectations for procedure complianCe, self-checking and independent verification will be reinforced. The subject test tap pipe caps will be labeled and added to the system checklist.
SAFETY SIGNIFICANCE
The containment hydrogen monitors are used to detect the buildup of hydrogen in the containment following an accident. This is accomplished by placing in service at least one of the two containment hydrogen monitoring channels (left channel procedurally preferred). If measured hydrogen concentration in the containment reaches between 1% and 3%, then procedures direct at least one hydrogen recombiner to be placed in service.
The analysis of record does not credit a hydrogen recombiner to be in service until 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after event initiation. Given that in an applicable accident, there would be concurrent challenged indications for containment pressure, containment temperature, reactor core temperature, and/or reactor vessel water level, it is reasonable to assume that a hydrogen recombiner would be placed in service within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> regardless of the existence of a valid containment hydrogen concentration indication from the containment hydrogen monitors. Rising radiation levels in the auxiliary building would also provide the operators an opportunity to identify the inoperable containment hydrogen monitor.
Additionally, recent analysis supporting proposed rulemaking for risk informed changes to 10 CFR 50.44, "Standards for combustible gas control in light-water-cooled power reactors," (Reference SECY-00-198 and SECY-02-0080) demonstrates that hydrogen recombiners serve little or no safety function in plants with large, dry containments. Since Palisades has a large, dry containment, this generic analysis is judged to be applicable.
The uninstalled test tap pipe caps also represented a potential radiological release path if the right channel containment hydrogen monitor had been placed in service following an accident involving an in-containment release of radioactive iodines. The calculated radiological release results for this condition are bounded by the integrated release in the existing analysis of record, given the expectation that the release path through the open test taps would be recognized and isolated within 12.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of event initiation.
Based on the above, the safety significance of this event was minimal.
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PREVIOUS SIMILAR EVENTS
None
NUCLEAR MANAGEMENT COMPANY
PALISADES NUCLEAR PLANT Fax Cover Sheet Date: � 2/20/03 Pages + Cover � 5 To: � Johnny Eads Company: � U. S. Nuclear Regulatory Commission Fax: � (301) 415-1222 Telephone: � (301) 415-1471 From: � Palisades Licensing Fax: � (269) 764-3265 Phone: � (269) 764-2426 Message: � LICENSEE EVENT REPORT 02-003, INOPERABLE
CONTAINMENT HYDROGEN MONITORS
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