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| Entered date | Event description | |
|---|---|---|
| ENS 54816 | 4 August 2020 22:43:00 | EN Revision Imported Date : 8/20/2020 BOTH SERVICE WATER HEADERS DECLARED INOPERABLE On 8/4/20, at 1745 EDT, Millstone Unit 2 entered technical specification (TS) 3.0.3 due to both service water headers being declared inoperable because strainer differential pressures (D/Ps) were greater than 9 psid. The high service water strainer D/P was the result of heavy debris impingement caused by tropical storm Isaias. To reduce heat loads and service water flow, Unit 2 reduced power to 75 percent. One service water header was restored to operable at 1816 EDT, at which time TS 3.0.3 was exited. At 1843 EDT both service water headers were declared operable. The NRC Resident Inspector has been notified.
The purpose of this call is to retract a report made on August 4, 2020, NRC Event Number EN 54816 describes a condition at Millstone Power Station Unit 2 (MPS2) in which both trains of service headers were declared inoperable due to service water strainer differential pressures greater than 9 psid. The condition was reported to the NRC pursuant to 10 CFR 50.72(b)(3)(v)(A), (B) and (D) via an 8 hour prompt report as an 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 shutdown the reactor and maintain it in a safe shutdown condition, remove residual heat and mitigate the consequences of an accident. Upon further review, MPS2 determined that there was no loss of safety function. An engineering evaluation supports the conclusion that a strainer differential pressure of 16 psid would not challenge the system flow distribution during worst case conditions. The evaluation also demonstrates that flowrates on both headers were observed to be unaffected during the timeframe of the high strainer differential pressure conditions. Therefore, both service water headers would have provided the required flows to perform their safety function. Therefore, this condition is not reportable and NRC Event Number EN 54816 is being retracted. The basis for this conclusion has been provided to the NRC Resident Inspector. Notified R1DO (Greives). |
| ENS 51187 | 28 June 2015 11:24:00 | During Security checks of Control Room doors, a boundary door was found not latched. This door is capable of being manually closed and latched. The door was in this condition for 4 hours and 25 minutes. The door is currently closed and latched. This is being reported as it could have prevented the fulfillment of a safety function to mitigate the consequences of an accident per 10 CFR 50.72(b)(3)(v)(D). The NRC Resident Inspector has been notified. A condition report has been written and the door is posted to require manual checks to ensure it is latched until the door closing mechanism is repaired.
Event Report number 51187 describes a condition at Millstone Power Station Unit 2 (MPS2) in which a control room environmental boundary door was found unlatched. This was reported in accordance with 10CFR 50.72(b)(3)(v)(D) as a condition that could have prevented the fulfillment of a safety function to mitigate the consequences of an accident. Upon further review, MPS2 has concluded that there was no loss of safety function, because even with the control room boundary door unlatched, the control room emergency ventilation system would have been able to perform its safety function during accident conditions. The MPS2 control room is pressure neutral and the hydraulic door closure mechanism was verified adequate to ensure the door would close and remain closed during accident conditions (even though it was not latching). Therefore, this condition is not reportable and NRC Event Number 51187 is being retracted. The basis for this conclusion will be provided to the NRC Resident Inspector. Notified the R1DO (Cahill). |