| Site | Start date | Title | Description |
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ENS 57090 | Browns Ferry | 25 April 2024 03:15:00 | Automatic Reactor Scram with Eccs Actuation | The following information was provided by the licensee via email:
On 4/24/2024 at 2215 CDT, Browns Ferry Unit 1 experienced an automatic reactor scram. The cause of the scram is currently under investigation. The main steam isolation valves (MSIVs) remain open with the main turbine bypass valves controlling reactor pressure. The reactor feedwater pumps are in service to control reactor water level.
Primary containment isolation systems (PCIS) Groups 2, 3, 6, and 8 isolation signals were received. Upon receipt of these signals, all components actuated as required. Following the reactor scram, due to reactor water level reaching minus 45 inches, both high pressure coolant injection (HPCI) and reactor core isolation cooling (RCIC) initiation signals were received, and both initiated as designed. All safety systems operated as expected.
This event requires a 4-hour report per 10 CFR 50.72(b)(2)(iv)(A), `Any event that results or should have resulted in emergency core cooling system (ECCS) discharge into the reactor coolant system as a result of a valid signal except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation.
This event requires a 4-hour report per 10 CFR 50.72(b)(2)(iv)(B), `Any event or condition that results in actuation of the reactor protection system (RPS) when the reactor is critical except when the actuation results from and is part of a pre-planned sequence during testing or reactor operation.
This event requires an 8-hour report per 10 CFR 50.72(b)(3)(iv)(A), `Any event or condition that results in valid actuation of any of the systems listed in paragraph (b)(3)(iv)(B): 1) Reactor protection system (RPS) including: reactor scram or reactor trip. 2) General containment isolation signals affecting containment isolation valves in more than one system or multiple main steam isolation valves (MSIVs). 4) ECCS for boiling water reactors (BWRs) - high-pressure coolant injection (HPCI). 5) BWR reactor core isolation cooling system (RCIC).
All safety systems operated as expected. At no time was public health and safety at risk. The NRC resident inspector has been notified.
The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
Units 2 and 3 were not affected. | ENS 56977 | Brunswick | 19 February 2024 04:25:00 | Automatic Start of Emergency Diesel Generator | The following information was provided by the licensee via phone and email:
At approximately 2325 EST on February 18, 2024, with Unit 1 in Mode 5 at 0 percent power and Unit 2 in Mode 1 at 100 percent power, emergency diesel generator 2 automatically started due to the unexpected loss of AC power to emergency bus E2 during a planned transfer of E2 DC control power from normal to alternate for the 1B-1 battery. In addition, the unexpected loss of AC power to E2 resulted in Unit 1 primary containment isolation system (PCIS) partial Group 2 (i.e., drywell equipment and floor drain, residual heat removal (RHR), discharge to radioactive waste, and RHR process sample), Group 6 (i.e., containment atmosphere control/dilution, containment atmosphere monitoring, and post accident sampling systems), and partial Group 10 (i.e., air isolation to the drywell) isolations.
Emergency diesel generator 2 automatically started and re-energized the E2 bus as designed when the loss of E2 signal was received. The PCIS actuations were as expected for the outage plant line up on Unit 1 at the time. The cause of the loss of electrical power to emergency bus E2 is under investigation at this time.
This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of emergency diesel generator 2 and PCIS.
There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.
The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
This event will be entered into the plant's corrective action program. | ENS 56936 | Peach Bottom | 29 January 2024 17:02:00 | Automatic Reactor Scram | The following information was provided by the licensee via email:
At approximately 1202 EST on 01/29/24, unit 2 experienced a reactor scram caused by a main turbine trip. Investigation is still ongoing.
The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
All control rods were fully inserted. The licensee indicated that the turbine trip may have been caused by a power load imbalance, however the cause of the incident is under investigation. The scram was not complex.
Decay heat is currently being removed thru bypass valves dumping to the main condenser. Initially unit 2 lost the use of the bypass valves due to lack of condenser vacuum. Unit 2 used the high pressure coolant injection (HPCI) system in the condenser storage tank (CST) to CST mode to remove decay heat. Residual heat removal was used to keep the torus cool. Condenser vacuum was regained and unit 2 is back to removing decay heat with the turbine bypass valves.
There was no impact to unit 3.
The licensee confirmed there was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified.
- * *UPDATE ON 01/29/24 AT 1935 EST FROM PAUL BOKUS TO NATALIE STARFISH* * *
The following information was provided by the licensee via email:
Licensee adds 8-hour non-emergency 10 CFR 50.72(b)(3)(iv)(A) specified system actuation report to original 4-hour non-emergency 10 CFR 50.72(b)(2)(iv)(B) RPS Actuation report.
At approximately 1202 EST on 01/29/24, unit 2 experienced a reactor scram by a main turbine trip. All control rods inserted. Reactor core isolation cooling system (RCIC) was manually initiated for level control. HPCI was manually initiated for pressure control. Primary containment isolation system (PCIS) Group II and III isolations occurred (specified system actuation). Investigation is ongoing.
The NRC Resident Inspector has been notified. | IR 05000333/2023010 | FitzPatrick | 26 October 2023 | Biennial Problem Identification and Resolution Inspection Report 05000333/2023010 | | ML23291A385 | Susquehanna | 12 October 2023 | 1 to Updated Final Safety Analysis Report, Chapter 6, Section 6.0, Engineered Safety Features | | ML23291A409 | Susquehanna | 12 October 2023 | 1 to Updated Final Safety Analysis Report, Chapter 6, Section 6.2, Containment Systems | | ML23292A129 | Susquehanna | 12 October 2023 | 1 to Updated Final Safety Analysis Report, Chapter 14, Section 14.2, Specific Information to Be Included in Final Safety Analysis Report | | ML23269A037 | | 18 September 2023 | FOIA-2023-000018 - Resp 1 - Final, Agency Records Subject to the Request Are Enclosed | | ML23174A144 | | 23 June 2023 | Knowledge and Abilities Catalog for Nuclear Power Plant Operators: Boiling Water Reactors | | NRC-23-0020, License Amendment Request for a Risk Informed Approach to ECCS Strainer Performance | Fermi | 13 June 2023 | License Amendment Request for a Risk Informed Approach to ECCS Strainer Performance | |
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