05000454/FIN-2013004-03
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Finding | |
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| Title | Ultimate Heat Sink Design Changes |
| Description | During inspection activities associated with the review of tornado protection of the UHS, the inspectors identified an Unresolved Item concerning the redundant design of the SXCTs. Specifically, the inspectors were interested in changes to the description of the UHS and how, over time, the descriptions changed, particularly as associated with an apparent change from a redundant SXCT design to a non-redundant design, without any associated physical SXCT modifications. Original design documents identified that the UHS was designed with sufficient capacity to permit it to perform its safety-related function following a passive failure of one of two SXCTs. In particular, the remaining SXCT was able to provide sufficient cooling to mitigate an accident on one unit coincident with the safe shutdown of the non-accident unit. During a design basis reconstitution of the UHS, the description of the UHS was revised and references to this design redundancy were eliminated. In particular, the final UHS design basis reconstitution report did not mention any intent or need to alter this characteristic of the UHS. Similarly, the safety evaluation associated with the license amendment for the UHS design basis reconstitution did not identify that a change occurred. The licensee entered this issue into their CAP as IR 1551720, NRC Questions Information Provided in 1992. At the end of the inspection period the inspectors were still evaluating whether the change in the description of the SXCTs was reflective of a corresponding change in UHS performance. If the performance of the UHS changed, the inspectors planned to evaluate whether such a change had been appropriately reviewed and approved. This issue is an Unresolved Item (URI 05000454/2013004-003; 05000455/2013004-003) pending the completion of that review. |
| Site: | Byron  |
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| Report | IR 05000454/2013004 Section 1R18 |
| Date counted | Sep 30, 2013 (2013Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.18 |
| Inspectors (proximate) | B Bartlett C Thompson E Duncan J Cassidy J Draper J Rivera J Robbins L Carson T Gob Bartlettc Thompson D Szwarc E Duncan J Benjamin J Cassidy J Draper J Mcghee J Robbins |
| INPO aspect | |
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Finding - Byron - IR 05000454/2013004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Byron) @ 2013Q3
Self-Identified List (Byron)
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