ENS 48181
ENS Event | |
|---|---|
04:44 Aug 12, 2012 | |
| Title | Technical Specification Required Shutdown Due to Ultimate Heat Sink Exceeding Temperature Limit |
| Event Description | Millstone Unit 2 reported that it is in a technical specification shutdown condition based on the ultimate heat sink average water temperature exceeding a temperature limit of 75 degrees Fahrenheit. The ultimate heat sink is supplied by water from Niantic Bay. At the time of this report, the bay water temperature is slightly below the 75 degree temperature limit but the time average calculation for the ultimate heat sink temperature limit still exceeds 75 degrees.
The Ultimate Heat Sink Technical Specification, TS 3.7.11.a, requires the unit to be in hot shutdown within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> when the average temperature limit is exceeded. The licensee is in a slow power ramp-down while monitoring the ultimate heat sink average temperature for water temperature conditions to drop below the limit. The high heat sink temperatures are based on natural environmental conditions and not from plant operation. Millstone Unit 3 is not impacted at this time. The licensee has notified State and local authorities and will notify the NRC Resident Inspector.
The licensee reported that it had exited the Technical Specification LCO based on a current average heat sink temperature below 75 F. However, the licensee will hold power at 65% to ensure the temperature is stable and will remain below the limit during the day shift. The licensee has notified the NRC Resident Inspector. R1DO (Burritt) notified.
At 0943 EDT on 8/12/12, the average ultimate heat sink temperature on Unit 2 exceeded the 75 degree limit again. The licensee re-entered TS LCO 3.7.11.a and commenced to shutdown the unit from a starting power level of 65%. The licensee plans to proceed to Hot Standby in compliance with the TS action statement even if the heat sink temperature drops back below the TS limit. The licensee has notified State and local authorities and the NRC Resident Inspector. R1DO (Burritt) notified.
At 1645 EDT on 8/12/12, Unit 2 is in Hot Standby and the heat sink temperature is below the 75 degree limit. The licensee has notified State and local authorities and the NRC Resident Inspector. R1DO (Burritt) notified. |
| Where | |
|---|---|
Millstone  Connecticut (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(2)(i), Tech Spec Required Shutdown | |
| Time - Person (Reporting Time:+-2.93 h-0.122 days <br />-0.0174 weeks <br />-0.00401 months <br />) | |
| Opened: | Richard Vigneah 01:48 Aug 12, 2012 |
| NRC Officer: | Bill Huffman |
| Last Updated: | Aug 12, 2012 |
| 48181 - NRC Website | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (66 %) |
WEEKMONTHYEARENS 544492019-12-18T00:29:00018 December 2019 00:29:00
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