05000361/FIN-2008010-02
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Finding | |
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Title | Inadequate Design Control for 125VDC Control Circuits |
Description | The team identified a noncited violation of 10 CFR 50, Appendix B, Criterion III, Design Control, for failure to properly analyze voltage drop in 125 Volts Direct Current control circuits. Specifically, the licensee failed to consider and analyze the voltage drop that occurs in control circuit elements such as cables, relay contacts, and fuses that could result in considerably lower voltage at the devices than is available at the corresponding distribution panels. The licensee has entered this into their corrective action program as Notifications NN 200051692 and NN 200059581. This finding is more than minor because it is associated with the mitigating systems cornerstone objective (design control attribute) of ensuring the availability and reliability of safety systems, and closely parallels inspection manual chapter 0612, Appendix E, Example 3.j, in that there was reasonable doubt regarding the capability of the 125 Volts Direct Current system to perform its intended function pending reanalysis. Using the Inspection Manual Chapter 0609, Significance Determination Process, Phase 1 Worksheets, the finding is determined to have very low safety significance (Green) because the 125 Volts Direct Current system was determined to have sufficient voltage margin to accommodate the additional voltage drop in the circuit elements that had not been considered. This finding was reviewed for crosscutting aspects and none were identified |
Site: | San Onofre |
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Report | IR 05000361/2008010 Section 1R21 |
Date counted | Sep 30, 2008 (2008Q3) |
Type: | NCV: Green |
cornerstone | Mitigating Systems |
Identified by: | NRC identified |
Inspection Procedure: | IP 71111.21 |
Inspectors (proximate) | L Ellershaw J Adams C Baron G Skinner P Gage R Bywater M Bloodgood D Reinert |
INPO aspect | |
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Finding - San Onofre - IR 05000361/2008010 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (San Onofre) @ 2008Q3
Self-Identified List (San Onofre)
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