ENS 48174
ENS Event | |
|---|---|
23:45 Aug 9, 2012 | |
| Title | Control Building A/C Unit May Not Perform Design Function on Loss of Redundant A/C Unit |
| Event Description | Affected equipment includes two 4160 volt safety buses, four 480 volt safety buses, four 120 volt AC safety trains, and four 125 volt DC safety trains.
Following an accident Class 1E AC Unit SGK05B may not be able to perform is design safety function if a single failure causes a loss of redundant Class 1E AC unit SGK05A. This is due to continued latent heat input from A train Control Room Pressurization Fan which continues to operate. SGK05A and B provide room cooling for all safety related electrical busses. Action Taken: Established the following compensatory measure - During accident conditions with both trains of CRVIS [Control Room Ventilation Isolation System] actuated if at any time SGKO5A trips then following completion of immediate actions Control Room pressurization fan CGK04A will be secured to reduce latent heat removal requirements for SGK05B. The licensee has notified the NRC Resident Inspector.
[On August 11, 2012 at 1845 CDT, the licensee identified] this condition applies to SGK05A. Action taken: Established compensatory measures that during an accident condition with both trains of CRVIS actuated, if at any time SGK05A or SGK05B trips for any reason then, following completion of immediate actions, Control Room pressurization fan on the same train with the tripped A/C unit will be secured if the other pressurization fan is running. The licensee notified the NRC Resident Inspector. Notified the R4DO (Drake).
Further engineering evaluation determined that the Class 1E AC unit SGK05A and SGK05B have the ability to remove the heat addition of the Control Room Pressurization Fans. As a result, the condition has been determined to not be reportable per 10 CFR 50.72(b)(3)(v)." The NRC Resident Inspector has been notified. Notified R4DO (Miller). |
| Where | |
|---|---|
Wolf Creek  Kansas (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+2.7 h0.113 days <br />0.0161 weeks <br />0.0037 months <br />) | |
| Opened: | James M. Kuras 02:27 Aug 10, 2012 |
| NRC Officer: | John Shoemaker |
| Last Updated: | Sep 19, 2012 |
| 48174 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |