05000456/FIN-2007009-04
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Finding | |
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| Title | Failure to Have Formal Documentation to Demonstrate the Cable Damage Resulting from Maximum Available Short Circuit Currents |
| Description | The power supply cables for the RHR and SI motors consist of 3C/No. 2 insulated copper conductors and share a common raceway. The magnitude and duration of the calculated maximum short circuit currents during postulated electrical faults at the motor terminals were compared with the cable time versus current damage curve to assess the short circuit current capability of the cable. This examination identified that the cable short circuit current capability was lower then the required capability to assure cable damage would not take place for faults at the motor terminals. Specifically, the review of the short circuit current capability curves indicated that the safe short circuit withstand time of the No. 2 copper cables for the calculated available fault currents is between 1 and 2 cycles. Review of the applied protective relaying and breaker tripping indicated that it would take between 5 and 6 cycles to isolate a postulated electrical fault at the RHR or at the SI motor terminals. The inspectors concluded that the fault clearing time exceeded the cable short circuit current carrying 16 Enclosure capability. The inspectors learned that the licensee had recognized that the RHR and SI cables were undersized for the short circuit current capability requirements and had adapted the practice of replacing these cables following electrical faults either the RHR or SI motor terminals. The inspectors reviewed the Sargent and Lundy (S&L) cable sizing acceptance criteria, Standard ESC-193 the licensee had used, and determined that the RHR and SI motor power supply cables were sized in accordance with the stated cable sizing acceptance criteria. The S&L cable sizing criteria required that the No. 2 cables of certain lengths be replaced in the event they carry short circuit currents during electrical faults at the motor terminals. The S&L Standard ESC-193 made reference to test results to support the acceptability of the licensees use of No. 2 size cables for the 4160 Vac power supplies to the RHR and SI pump motors. However, the S&L test data was not available for review. The licensee provided a preliminary calculation results which indicated that the No. 2 cables could withstand electrical faults for up to 90 seconds before compromising the functional capability of other cables in common raceways. This issue is considered an Unresolved Item (URI 05000456/2007009-04(DRS);05000457/2007009-04(DRS)) pending the inspectors review of the test data or final licensee calculation. |
| Site: | Braidwood  |
|---|---|
| Report | IR 05000456/2007009 Section 1R21 |
| Date counted | Sep 30, 2007 (2007Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | D Schrum B Jose J Jacobson T Bilik C Brown L Kozak J Chiloyan S Traiforosm Mitchellb Metrow A Garmore M Perry D Lords R Jones G Roach R Jickling S Ray B Jose J Jacobson T Bilik |
| INPO aspect | |
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Finding - Braidwood - IR 05000456/2007009 | |||||||||||||||||
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Finding List (Braidwood) @ 2007Q3
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