ENS 51240
ENS Event | |
|---|---|
17:14 Jul 18, 2015 | |
| Title | Standby Gas Treatment System Declared Inoperable Due to Inoperable Sump Pumps |
| Event Description | At 1214 CDT on 7/18/2015, during normal surveillance testing of Z sump, Z2 sump pump run time was found to exceed its upper Augmented IST limit, rendering it non-functional. Operators continued with the surveillance, opening the power supply breaker to Z1 sump pump, rendering it non-functional also. When this was identified, station personnel backed out of testing and restored power to Z1 sump pump. Z sump functions to limit condensation buildup in the common Standby Gas Treatment System (SGT) discharge line to support SGT operability. One sump pump is required to be functional to support SGT operability. With both Z sump pumps non-functional, operability of both trains of SGT is not assured. Loss of both trains of SGT constitutes a loss of safety function for control of rad release and accident mitigation per 10 CFR 50.72(b)(3)(v) functions (C) and (D).
The breaker for Z1 sump pump was reclosed at 1225 CDT, restoring functionality to Z1 sump pump and operability to both trains of SGT. Both Z sump pumps were considered non-functional and unable to support SGT operability for a period of 11 minutes. The licensee notified the NRC Resident Inspector.
Cooper Nuclear Station (CNS) is retracting the 8-hour non-emergency notification made on July 18, 2015 at 1839 EDT (EN# 51240). The notification on July 18, 2015 reported a condition where the two Z Sump Pumps were considered non-functional and unable to support the operability of the Standby Gas Treatment System (SGT). Subsequent evaluation concluded that Z2 Sump Pump was functional with the run time identified and would have supported the operability of SGT during the time the Z1 Sump Pump breaker was open for surveillance testing. A loss of safety function did not exist. A modification had been previously installed at CNS that prevents the buildup of significant amounts of water in a hold-up line. This volume of water was the basis for the original Z Sump Pump IST [in-service-testing] run times. With the buildup of water previously resolved, the calculated Z Sump Pump IST run times are much longer than measured on July 18, 2015. Notified the R4DO (Hagar). |
| Where | |
|---|---|
Cooper  Nebraska (NRC Region 4) | |
| Reporting | |
| 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:+1.42 h0.0592 days <br />0.00845 weeks <br />0.00195 months <br />) | |
| Opened: | Steve Wheeler 18:39 Jul 18, 2015 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Aug 18, 2015 |
| 51240 - NRC Website | |
Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |