Semantic search

The following information was provided by the licensee via email: At 0227 EST on 11/16/23, Calvert Cliffs Unit 2 experienced an automatic trip from the reactor protection system (RPS) based on reactor trip bus undervoltage (UV). At that time, a loss of U-4000-22 (13 kV to 4 kV transformer) caused a loss of 22, 23, and 24 4 kV busses. This resulted in a loss of both motor generator (MG) sets causing the reactor trip bus UV. The loss of 22 and 23 4 kV non-safety related busses resulted in a loss of main feedwater. Auxiliary feedwater (AFW) was manually initiated and is feeding both steam generators. The 2B diesel generator (DG) started and restored the 24 4 kV safety related bus. Heat removal is via the normal turbine bypass valves to the main condenser. RPS actuation is reportable under 10 CFR 50.72(b)(2)(iv)(B) - 4 hour report ESFAS (engineering safety features actuation system) actuation (2B DG start on UV) is reportable under 10 CFR 50.72(b)(3)(iv)(A) - 8 hour report AFW operation is reportable under 10 CFR 50.73(a)(2)(iv)(A) - 60 day report The NRC Senior Resident Inspector has been notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: All rods fully inserted. There was no impact on Unit 1 operations. Unit 2 is stable in mode 3.

• * * UPDATE ON AT 0940 EST FROM KERRY HUMMER TO ADAM KOZIOL * * *

ESFAS actuation (AFW manual initiation) is reportable under 10CFR50.72(b)(3)(iv)(A) - 8 hour report Notified R1DO (Defrancisco).

The following information was provided by the licensee via email: At 0449 (EDT) on 7/12/2023, Millstone Unit 3 declared the 'B' train of the emergency core cooling system (ECCS) inoperable due to a degraded damper associated with the ventilation support system for the 'B' charging pump. At the time of this event, the 'A' train of service water was already inoperable due to planned maintenance on a breaker that would have prevented an 'A' service water valve powered from this breaker from closing on a safety signal. This configuration resulted in the possibility that the 'A' train of ECCS would not have been available to fulfill its design function under all postulated accident conditions. This event is being reported under 10 CFR 50.72(b)(3)(v)(B), '(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: (B) remove residual heat).' Subsequently, the 'A' train of service water was restored to operable at 0548 on 7/12/2023. Repairs and investigation continue on the 'B' train ECCS damper. The NRC resident has been notified. This event did not impact Millstone Unit 2. There was no impact to the public.

• * * RETRACTION ON 7/31/2023 AT 1400 EDT FROM JAMES KELLY TO JOHN RUSSELL* * *

The following information was provided by the licensee via email: The condition was reported to the NRC pursuant to 10 CFR 50.72(b)(3)(v)(B), via an 8-hour 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 remove residual heat. A subsequent engineering review of the conditions that existed at the time determined that, based on area temperature response, any impact on ventilation flows into and out of the `B' charging pump cubicle did not generate an observable change in the temperature trend. Based on this, it is concluded with reasonable assurance that the functional requirement of the support system was maintained and the `B' charging pump would have continued to perform its safety function until the `A' train of service water was restored to operable and as a result safety function was not lost. Therefore, this condition is not reportable and NRC Event Number 56620 is being retracted. The basis for this conclusion has been provided to the NRC Resident Inspector." Notified R1DO (Bicket).

The following information was provided by the licensee via fax: On March 14, 2023, at 2000 EDT, in accordance with 10 CRFR 50.72(b)(3)(xiii). Yankee Nuclear Power Station Independent Spent Fuel Storage Installation (ISFSI) determined that the impacts of a severe winter storm have resulted in a major loss in off site response capability. Since approximately 0200, very heavy snow has fallen and greater than two feet has accumulated on site. All security related equipment has remained functional, and there have been no impacts to methods of offsite communications or emergency assessment capability. The concrete cask heat removal systems have remained operable in accordance with the NAC International multi-purpose container system (NAC-MPC) technical specifications. From approximately 0550 until 1840, offsite power was lost, and the site was powered by the security diesel generator. Periodically throughout the day, the Security Shift Supervisor was in contact with State and local police to ensure response capability. At the 2000 hours update, the law enforcement agencies reported that there were recent reports of trees and power lines being downed by the weight of the snowfall causing road closures and significantly impacting routes and response times to the site. The site remains fully staffed.

• * * UPDATE ON 3/17/2023 AT 1647 EDT FROM LLOYD BROOKS TO ERNEST WEST * * *

On March 14, 2023, at 2000 EDT, in accordance with 10 CFR 50.72(b)(3)(xiii), Yankee Nuclear Power Station Independent Spent Fuel Storage Installation determined that the impacts of a severe winter storm resulted in a major loss in offsite response capability. Downed trees and power lines in conjunction with up to thirty-six (36) inches of snow prevented vehicle passage on normal response routes. On March 15, 2023, at approximately 1700 EDT, these roadways were passable, and employees and emergency vehicles regained normal access to the site. However, the Town of Rowe, Massachusetts police chief informed the site that the town remained in an emergency status and the roadways may need to be intermittently closed in order for utility workers to restore power lines and continue to clear tree limbs. On March 16, 2023, 1815 EDT, the Town of Rowe, Massachusetts police chief secured from the emergency. Therefore, this update is to inform the NRC that the Yankee Nuclear Power Station Independent Spent Fuel Storage Installation has similarly returned to baseline operations. NRC Region I management has been updated throughout the progression of the storm and recovery. A press release is not anticipated. Notified R1DO (Bickett)

The following information was provided by the licensee via phone call and email: At 0800 on February 12, 2023, it was discovered that both trains of control room emergency ventilation system were simultaneously inoperable due to a safety injection relief valve discharging to a Unit 1 sump. This leakage in conjunction with design basis loss of coolant accident may result in radiological dose exceeding limits to the exclusion area boundary and to the control room, which is common to both Unit 1 and Unit 2. Therefore, this condition is being reported as an eight-hour, nonemergency notification per 10 CFR 50.72(b)(3)(ii)(B) and 10 CFR 50.72(b)(3)(v)(D) as an 'Unanalyzed Condition and a Condition that Could Have Prevented Fulfillment of a Safety Function.' There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.

• * * RETRACTION FROM ROBERT TAYLOR TO DONALD NORWOOD AT 0530 EDT ON 3/17/2023 * * *

Retraction of EN56350, Control Room Emergency Ventilation System Inoperable: Based on subsequent evaluation, it was determined that the control room emergency ventilation system remained operable due to the maximum measured leak rate being within the bounds of the analysis. The maximum measured leak rate of 32,594 cc/hr from the safety injection system did not challenge the calculated maximum engineered safety features leak rate of 45,600 cc/hr and remained within the current dose analysis limits. As such, this was not an unanalyzed condition and did not prevent the fulfillment of a safety function to mitigate the consequences of an accident. The NRC Resident Inspector has been notified. Notified R1DO (Bickett).