05000390/FIN-2015002-05
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Finding | |
|---|---|
| Title | Review of 10 CFR 50.59 Evaluation for the Emergency Diesel Generator Heat Exchanger |
| Description | The inspectors identified an unresolved item (URI) regarding the licensees 10 CFR 50.59 evaluation for a modification to the operational configuration of the inlet motor operated valves (MOVs) for the EDG Heat Exchanger. Additional inspection would be required to determine if the licensees 10 CFR 50.59 evaluation properly addressed whether the modification resulted in more than a minimal increase in the likelihood of occurrence of a malfunction of a structures, systems, or components (SSCs) important to safety previously evaluated in the UFSAR. Watts Bar has four EDGs that are each cooled by two heat exchangers supplied by the ERCW system. Prior to the modification, flow through the heat exchangers was continuous due to the inlet MOVs (1-FCV-067-0066-A, 2-FCV-067- 0066-A, 1-FCV-067-0067-B and 22FCV-067-0067-B) being locked open. In order to ensure sufficient flow is available to components served by ERCW during dual-unit operations, the licensee modified the position of these MOVs from normally open with power removed, to normally closed with breakers closed. This resulted in the EDG heat exchangers being isolated during normal operation from the ERCW system. Flow, however, would be restored by the MOVs active function to open upon receipt of a signal from the EDG speed switch, should the EDGs startup. The inspectors reviewed the results of the licensees 10 CFR 50.59 evaluation related to the impact of the modification on the failure probability of the EDG. The inspectors concluded that additional information and review was necessary to determine whether the modification resulted in more than a minimal increase in the likelihood of occurrence of a malfunction of a system, structure, or component important to safety previously evaluated in the UFSAR. Particularly, the inspectors needed additional information on the specific inputs, assumptions, and evaluation methodology used to determine the increase in EDG failure probability. This issue was identified as URI 05000390/2015002-05, Review of 10 CFR 50.59 Evaluation for the EDG Heat Exchanger. |
| Site: | Watts Bar  |
|---|---|
| Report | IR 05000390/2015002 Section 1R07 |
| Date counted | Jun 30, 2015 (2015Q2) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.07 |
| Inspectors (proximate) | A Blarney C Cheung J Eargle J Hamman J Nadel J Rivera-Ortiz P Cooper R Egli R Hickok T Palmer W Russella Blameya Nielsen C Even E Patterson J Eargle J Hamman J Nadel J Panfel J Rivera-Ortiz M Magyar M Read P Cooper R Baldwin R Carrion W Pursley |
| INPO aspect | |
| Finding closed by | |
| IR 05000390/2000391 (12 February 2016) | |
| ' | |
Finding - Watts Bar - IR 05000390/2015002 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Watts Bar) @ 2015Q2
Self-Identified List (Watts Bar)
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