05000255/LER-2003-004, Inoperable Train of Containment Cooling - Condition Prohibited by Technical Specifications
| ML032550350 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 08/28/2003 |
| From: | Cooper D Nuclear Management Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER 03-004-00 | |
| Download: ML032550350 (4) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2552003004R00 - NRC Website | |
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Palisades Nuclear Plant Operated by Nuclear Management Company, LLC August 28, 2003 10 CFR 50.73 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 PALISADES NUCLEAR PLANT DOCKET 50-255 LICENSE No. DPR-20 LICENSEE EVENT REPORT 03-004 - INOPERABLE TRAIN OF CONTAINMENT COOLING - CONDITION PROHIBITED BY TECHNICAL SPECIFICATIONS Licensee Event Report (LER)03-004 is attached. The LER describes the inoperability of one train of containment cooling in excess of the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> allowed outage time. This occurrence is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.
This letter contains one new commitment and no revisions to existing commitments.
The new commitment is:
The containment air cooler fans and motors will be included in the predictive maintenance program Douglas E. Cooper Site Vice-President, Palisades Plant CC Regional Administrator, USNRC, Region III Project Manager, Palisades Plant, USNRC, NRR NRC Resident Inspector - Palisades Plant Attachment 27780 Blue Star Memorial Highway
- Covert, Michigan 49043-9530 Telephone: 269.764.2000 Tepq-
Abstract
On July 1, 2003, at 0414 hours0.00479 days <br />0.115 hours <br />6.845238e-4 weeks <br />1.57527e-4 months <br />, with the plant in mode 1, containment air cooler recirculation fan V-4A tripped unexpectedly and was declared inoperable, causing its associated containment cooling train to also become inoperable.
Technical Specification (TS) 3.6.6, condition A, requires that with one or more containment cooling trains inoperable, restore the train(s) to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Condition B of TS 3.6.6 requires that if condition A cannot be met, be in mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in mode 4 within 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
Nuclear Management Company, LLC, requested, and was granted, enforcement discretion from the NRC to not enforce compliance with the required actions of condition B for up to an additional 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> to avoid a plant shutdown that would impose an unnecessary plant transient without a significant offsetting safety benefit.
V-4A was subsequently retumed to operable status on July 6, 2003, at 1404 hours0.0163 days <br />0.39 hours <br />0.00232 weeks <br />5.34222e-4 months <br />.
Since the 72-hour completion time of TS 3.6.6 condition A was exceeded, this occurrence is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.
NRC FORM 366 (7-2001)
F Iff more space is required, use additional copies of NRC Farm 366A)
EVENT DESCRIPTION
On July 1, 2003, at 0414 hours0.00479 days <br />0.115 hours <br />6.845238e-4 weeks <br />1.57527e-4 months <br />, with the plant in mode 1, containment air cooler recirculation fan V-4A [CLRJ [FAN] tripped unexpectedly and was declared inoperable, causing its associated containment cooling train [BK1 to also become inoperable.
Technical Specification (TS) 3.6.6, condition A, requires that with one or more containment cooling trains inoperable, restore the train(s) to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Condition B of TS 3.6.6 requires that if condition A cannot be met, be in mode 3 within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in mode 4 within 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
Nuclear Management Company, LLC, requested, and was granted, enforcement discretion from the NRC to not enforce compliance with the required actions of condition B for up to an additional 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> to avoid a plant shutdown that would impose an unnecessary plant transient without a significant offsetting safety benefit.
V-4A was subsequently returned to operable status on July 6, 2003, at 1404 hours0.0163 days <br />0.39 hours <br />0.00232 weeks <br />5.34222e-4 months <br />.
Since the 72-hour completion time of TS 3.6.6, condition A, was exceeded, this occurrence is reportable in accordance with 10 CFR 50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.
CAUSE OF THE EVENT
The V-4A motor drive end bearing failed. The cause of the failure was determined to be normal fatigue accelerated by grease contamination. The containment air cooler fans and motors were not included in the predictive maintenance program. This prevented the identification and trending of V-4A's degrading condition so that corrective action could be taken to preclude a failure.
CORRECTIVE ACTIONS
The V-4A motor was replaced.
The containment air cooler fans and motors will be included in the predictive maintenance program.
(If more space Is required, use additional copies of NRC Fomi 3664)
SAFETY SIGNIFICANCE
The containment air cooler system includes four air handling and cooling units, referred to as containment air coolers (CACs). Three of the CACs (VHX-1, VHX-2 and VHX-3) are safety related coolers. The fourth CAC (VHX-4) is not taken credit for in maintaining post accident containment temperature within limits, but is used along with the other three CACs to maintain containment temperature during normal operation.
The post accident CAC safety-related fan units (V-1A, V-2A, V-3A and V-4A) serve not only to provide forced flow for their associated cooler, but also to provide mixing of the containment atmosphere. Since CAC VHX-4 has no credited cooling function, its associated safety related fan (V-4A) is only credited by the safety analysis in assisting in the containment atmosphere mixing function.
However, several industry data sources have shown adequate containment mixing occurs when considering the turbulent effects inside containment resulting from blowdown and operation of the containment sprays. The turbulent nature of the containment atmosphere following an accident with containment spray will serve to mix any unsprayed areas and equalize any differences in radionuclide concentrations between sprayed and unsprayed areas. Therefore, the assumption that the containment atmosphere is a single, uniformly mixed volume remains valid, providing the containment spray system is in operation.
While V-4A is credited in the safety analysis for mixing, the probabilistic safety assessment (PSA) analysis does not credit V-4A as a necessary condition for mixing. Rather, given the availability of the containment spray system, mixing would occur once the containment sprays are initiated.
Therefore, there is no impact on the performance of equipment modeled in the PSA.
PREVIOUS SIMILAR EVENTS
None.