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| Entered date | Event description | |
|---|---|---|
| ENS 42782 | 17 August 2006 17:33:00 | At 1044 on August 17, 2006, operators received main control room annunciator alarm 'CONDENSER VACUUM LOW' and status lights 'COND VACUUM TRIP' and 'COND VACUUM LOW.' All other indications for main condenser vacuum indicated normal ~ 26.6 (inches Hg). In response to the alarm, initial troubleshooting determined that the main turbine bypass system was inoperable. This was due to concluding that with the low condenser signal present, the bypass valves were prohibited from opening upon demand. Therefore at 1110, Technical Specifications 3.7.6, 'Main Turbine Bypass System,' Condition 'A' was entered. This is reportable as an 8 hour report in accordance with 10 CFR 50.72 (b)(3)(v)(D) as 'Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to: (D) Mitigate the consequences of an accident.' The devices that cause the annunciator are 1PY-ES063 and 1PY-ES066. A visual inspection of the device cards revealed that on the 1PY-ES066 card the 'DC CURRENT ALARM' upper and lower lights were lit. These same lights were not lit on the 1PY-ES063. At 1212 on August 17,2006, a lead was lifted to remove the low vacuum inhibit input from 1PY-ES066 for the bypass valves. The main control room alarm cleared and the low vacuum light went out as expected. At 1215 the low vacuum inhibit was reset restoring the bypass valves to operable. The licensee will notify the NRC Resident Inspector. |