EN Revision Imported Date : 8/20/2020
EN Revision Text: 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.
* * * RETRACTION ON 8/19/2020 AT 1141 EDT FROM ERIC DONCH TO KIRBY SCALES * * *
"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).