ENS 48063
ENS Event | |
|---|---|
20:51 Jul 2, 2012 | |
| Title | Both Diesel Generators Declared Inoperable |
| Event Description | D1 and D2 Diesel Generators (DG) were declared inoperable at 1551 CDT due to exceeding the maximum outside air temperature limit of 97 degree F. This limit was based on heatup analysis for a HELB [High Energy Line Break] in the turbine building. The temperature is measured using the 15 min average of air temperature at the 10 meter meteorological tower, which approximates the intake height for room ventilation.
LCO 3.8.1 Condition B was entered for both DGs and LCO 3.8.1 Condition E was entered for two DGs inoperable on the same unit. The DGs could start and run if required at the time of entry. This condition is reportable per 10 CFR 50.72(b)(3)(v) as an event or condition that could have prevented the fulfillment of a safety function. During review of the analysis, two pressure switches on D2 and one on D1 were identified as being limiting and a modification was approved to replace them. Upon replacement, the limiting outside temperature would increase to 100.5 degree F. Replacement of components had been completed for D2 diesel generator prior to LCO entry; however, the temperature limit of 100.5 degree F had not yet been approved. Shortly after D1 was declared inoperable, it was isolated to complete the component replacement which is expected to take less than four hours. D1 will return to operable once the component replacement and PMT is completed. At 1630 [CDT] D2 was declared operable based on approval of a revised operability recommendation that raised the outside temperature limit to 100.5 degree F. Outside air temperature peaked at 97.1 degree F and is slowly decreasing. The licensee has notified the NRC Resident Inspector.
Event Notification 48063 reported that D1 and D2 Diesel Generators (DG) were inoperable due to exceeding the maximum outside air temperature limit of 97 degree F. An additional approved evaluation determined that the D2 lube oil pressure switches were replaced prior to exceeding the outside ambient air temperature limit. The new lube oil pressure switches have a higher temperature rating that supports a higher outside ambient air temperature, therefore, D2 was able to fulfill its safety function and Event Notification 48063 is retracted. The NRC Resident Inspector has been informed. Notified R3DO (Cameron). |
| Where | |
|---|---|
Prairie Island  Minnesota (NRC Region 3) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor | |
| Time - Person (Reporting Time:+-2.15 h-0.0896 days <br />-0.0128 weeks <br />-0.00295 months <br />) | |
| Opened: | John Kempkes 18:42 Jul 2, 2012 |
| NRC Officer: | Dong Park |
| Last Updated: | Aug 28, 2012 |
| 48063 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |