05000382/FIN-2011007-06
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Finding | |
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Title | Failure to Establish an Analysis of the Effect of Reverse Rotation of Dry Cooling Tower Fan Motors Resulting from a Tornado Event |
Description | The team identified a Green violation of 10 CFR Part 50, Appendix B, Criterion III, Design Control, which states, in part, that measures shall be established to assure that applicable regulatory requirements and the design basis are correctly translated into specifications, drawings, procedures, and instructions. The design control measures shall provide for verifying or checking the adequacy of design, such as by the performance of design reviews, by the use of alternate or simplified calculational methods, or by the performance of a suitable testing program. Specifically, prior to October 7, 2011, the licensee failed to analyze the dry cooling tower fan motors for premature trip as a result of reverse rotation caused by a tornado event that could result in the loss of the dry cooling tower heat removal capability. This finding was entered into the licensees corrective action program as Condition Report CR-WF3-2011-06850. The team determined that the failure to establish and maintain an analysis supporting the ability of the dry cooling tower fan motors to operate successfully during and following a design basis tornado event was a performance deficiency. This finding was more than minor because it was associated with the design control attribute of the Mitigating Systems Cornerstone and affected the cornerstone objective of ensuring the availability, reliability, and capability of systems that respond to initiating events to prevent undesirable consequences. Specifically, the design basis analysis did not ensure that the dry cooling tower fan motors would perform as required under reverse rotation conditions, without premature trip, during a design basis tornado. In accordance with NRC Inspection Manual Chapter 0609, Attachment 4, Phase 1 Initial Screening and Characterization of Findings, the issue was determined to have very low safety significance (Green) because it was a design or qualification deficiency confirmed not to result in loss of operability or functionality. Specifically, the licensee prepared an evaluation of the effect on fan motor starting current and duration for reverse rotation conditions. For reverse rotation conditions that would extend the locked rotor current time by a factor of two, the licensees analysis showed ample margin for the instantaneous trip settings from the magnetic-only breaker and the thermal overload protection, such that premature trip would be precluded. This finding did not have a crosscutting aspect because the most significant contributor did not reflect current licensee performance. |
Site: | Waterford |
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Report | IR 05000382/2011007 Section 1R21 |
Date counted | Dec 31, 2011 (2011Q4) |
Type: | NCV: Green |
cornerstone | Mitigating Systems |
Identified by: | NRC identified |
Inspection Procedure: | IP 71111.21 |
Inspectors (proximate) | C Smith T Farnholtz W Sifre J Leivo E Uribe N Hernandez |
INPO aspect | |
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Finding - Waterford - IR 05000382/2011007 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Waterford) @ 2011Q4
Self-Identified List (Waterford)
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