ENS 46925
ENS Event | |
|---|---|
20:14 Jun 4, 2011 | |
| Title | Both Control Structure Chillers Out of Service |
| Event Description | On 06/04/2011, personnel observed the temperature control valve for the 'B' control structure chiller not operating properly. To investigate control valve operation, the controller was taken to the manual mode (from automatic) at 1614 [EDT]. The control valve stem was lubricated, and the valve was operated with the controller in the manual mode. The 'B' control structure chiller was inoperable in this condition until control valve responsiveness was validated (total of 35 minutes, until 1649 [EDT]). The 'B' chiller continued to operate during this period.
The 'A' control structure chiller was out of service during this timeframe to perform maintenance activities. Hence, neither chiller was operable. The control structure chillers provide control building habitability during unit operation. The control structure chillers also provide cooling water for emergency switchgear room cooling on unit one only. This condition is being reported as an event or condition that could have prevented fulfillment of a safety function per 10CFR 50.72(b)(3)(v)(D). The licensee has notified the NRC Resident Inspector.
On June 4, 2011, Susquehanna reported the simultaneous inoperability of both control structure (CS) chillers as an event or condition that could have prevented fulfillment of a safety function in accordance with 10CFR 50.72(b)(3)(v)(D). After further investigation, Susquehanna has concluded that the 'A' and 'B' CS chillers were not inoperable at the same time. On June 3, 2011 at 1608, fluctuating amperage was observed on the 'A' CS chiller and the chiller was declared inoperable. As a result, the 'B' CS chiller was placed in service with the 'A' CS chiller placed in standby. Subsequent troubleshooting of the 'A' CS chiller included replacing the chiller temperature controller with a spare while the original controller was evaluated in the shop. The original controller was re-installed on June 4, 2011 at approximately 1030 but did not resolve the issue. The 'A' CS chiller was later shutdown and removed from standby on June 4, 2011 at 1727. Originally, Susquehanna believed that the fluctuating amperage on the 'A' chiller was an operability issue. Subsequent engineering evaluation has determined that the observed oscillations were not rapid enough and did not have sufficient amplitude to cause damage to the chiller motor and were within design limits. The conclusion is that the 'A' control structure chiller was operable and would continue to operate for its 30 day mission time with the observed current oscillations. Although the 'A' chiller was inoperable as a result of troubleshooting at various times on June 3 and 4, the 'A' chiller was available and operable during the short period of time on June 4 when the 'B' chiller was inoperable. . Based on the above information, this ENS report is retracted. The licensee notified the NRC Resident Inspector. Notified the R1DO (Dentel). |
| Where | |
|---|---|
Susquehanna  Pennsylvania (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+2.85 h0.119 days <br />0.017 weeks <br />0.0039 months <br />) | |
| Opened: | Martin Lichtner 23:05 Jun 4, 2011 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Jul 22, 2011 |
| 46925 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |
Unit 2 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Cold Shutdown (0 %) |
| After | Cold Shutdown (0 %) |