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ENS 57822
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Category
ENS Notification  and Power Reactor
CFR
10 CFR 50 +, 10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation +, 10 CFR 50.72(b)(3)(iv)(A), System Actuation +, 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge +, 10 CFR 50.72#b2ivB +  and 10 CFR 50.72#b3ivA +
Current power
0  +
Description
The following information was provided by … The following information was provided by the licensee via phone and email:</br>At 1510 (EDT) with Unit 1 in mode 1 at 96 percent reactor power, the reactor was manually scrammed due to loss of main transformer cooling. The scram was not complex, all systems responded normally post-scram. Main turbine bypass valves opened automatically to maintain reactor pressure. </br>Operations responded to stabilize the plant. High pressure coolant injection momentarily injected into the reactor vessel and was subsequently placed in standby. Reactor water level has stabilized and is being maintained with the '1B' reactor feed pump. Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves. Unit 2 was not impacted. Due to the reactor protection system actuation while critical and the emergency core coolant system discharge to the reactor coolant system, this event is being reported as a four-hour and eight-hour non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B), 10 CFR 50.72(b)(2)(iv)(A), and 10 CFR 50.72(b)(3)(iv)(A). </br>The Unit 1 reactor is currently stable in mode 3. An investigation is in progress into the cause of the loss of main transformer cooling. There was no impact to the health or safety of the public or plant personnel. The NRC Resident Inspector has been informed. The state of Pennsylvania has been informed.e state of Pennsylvania has been informed.  +
Discovered date
19:10:00, 22 July 2025  +
ENS id number
57,822  +
Emergency class
Non Emergency +
Entered date
17:22:00, 22 July 2025  +
Event date
19:10:00, 22 July 2025  +
Event description
The following information was provided by … The following information was provided by the licensee via phone and email:</br>At 1510 (EDT) with Unit 1 in mode 1 at 96 percent reactor power, the reactor was manually scrammed due to loss of main transformer cooling. The scram was not complex, all systems responded normally post-scram. Main turbine bypass valves opened automatically to maintain reactor pressure. </br>Operations responded to stabilize the plant. High pressure coolant injection momentarily injected into the reactor vessel and was subsequently placed in standby. Reactor water level has stabilized and is being maintained with the '1B' reactor feed pump. Decay heat is being removed by discharging steam to the main condenser using the turbine bypass valves. Unit 2 was not impacted. Due to the reactor protection system actuation while critical and the emergency core coolant system discharge to the reactor coolant system, this event is being reported as a four-hour and eight-hour non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B), 10 CFR 50.72(b)(2)(iv)(A), and 10 CFR 50.72(b)(3)(iv)(A). </br>The Unit 1 reactor is currently stable in mode 3. An investigation is in progress into the cause of the loss of main transformer cooling. There was no impact to the health or safety of the public or plant personnel. The NRC Resident Inspector has been informed. The state of Pennsylvania has been informed.e state of Pennsylvania has been informed.  +
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ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +, ENS 57822 +  and ENS 57822 +
Initial power
96  +
LER
05000387/LER-2025-001, Manual Reactor Scram Following Partial Loss of Cooling to Main Transformer +, 05000387/LER-2025-001-01, (SSES) Unit 1, Manual Reactor Scram Following Loss of Cooling to Main Transformer +, Manual Reactor Scram Following Partial Loss of Cooling to Main Transformer +, (SSES) Unit 1 +  and Manual Reactor Scram Following Loss of Cooling to Main Transformer +
Last update date
00:00:00, 22 July 2025  +
Modification date"Modification date" is a predefined property that corresponds to the date of the last modification of a subject and is provided by <a rel="nofollow" class="external text" href="https://www.semantic-mediawiki.org/wiki/Help:Special_properties">Semantic MediaWiki</a>.
11:20:21, 24 July 2025  +
NRC officer
Brian P. Smith +
Notification date
17:22:00, 22 July 2025  +
Originated by
Ken Hulbert +
Reactor critical
true  +
Reactor scram
true  +
Reactor type
GE-4 +
Region
NRC Region 1 +
Reporting criterion
10 CFR 50.72(b)(2)(iv)(B), RPS System Actuation +, 10 CFR 50.72(b)(3)(iv)(A), System Actuation +  and 10 CFR 50.72(b)(2)(iv)(A), System Actuation - ECCS Discharge +
Reporting time
-0.075 d (-1.8 hours, -0.0107 weeks, -0.00247 months)  +
Scram
Manual Scram +
Site
Susquehanna +
Start date
19:10:00, 22 July 2025  +
State
Pennsylvania +
System
Reactor Coolant System +, High Pressure Coolant Injection +, Reactor Protection System +, Main Transformer +  and Main Condenser +
Title
Manual Reactor Scram  +
Turbine component
Turbine bypass valve +
URL"URL" is a <a href="/Special:Types/URL" title="Special:Types/URL">type</a> and predefined property provided by <a rel="nofollow" class="external text" href="https://www.semantic-mediawiki.org/wiki/Help:Special_properties">Semantic MediaWiki</a> to represent URI/URL values.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2025/20250724en.html#en57822  +
Unit
1  +
 
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