ENS 49141
ENS Event | |
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09:04 Apr 24, 2013 | |
Title | 60-Day Optional Telephone Notification for an Invalid Specified System Actuation |
Event Description | This 60-day telephone notification is being made per the reporting requirements specified in 10CFR50.73(a)(2)(iv)(A) and 10CFR50.73(a)(1) to report an event involving an invalid actuation signal affecting the Auxiliary Feedwater (AFW) and Essential Service Water (ESW) systems.
Initial conditions on 04/24/2013: refueling outage was in progress, there was no fuel in the reactor vessel (No MODE), a B safety-related train outage was in progress, and the A ESW train was in operation to support cooling of the A train safety-related equipment. Some separation group 2 bistables were in a tripped condition because instrument power bus NN02 was de-energized. At approximately 0400 [CDT] on 04/24/2013, Separation Group 4 DC bus NK04 experienced a ground condition. Plant personnel were using a plant procedure to search for the ground. When breaker NK5409 was opened, some unexpected Engineered Safety Features Actuation System (ESFAS) signals occurred. Opening the breaker removed power to the B ESFAS cabinet. With power removed to the B ESFAS cabinet, the circuit cards that generate cross-train trips failed to a tripped condition (thus generating cross-train trip signals) which resulted in some A train ESFAS actuations, in particular, auxiliary feedwater actuations for the A motor-driven and the turbine-driven AFW pumps. Additionally, an AFW Low Suction Pressure (LSP) circuit card tripped, and when combined with the bi-stable that was in a tripped state because bus NN02 was de-energized, the 2-out-of-3 logic was made up, resulting in an auxiliary feedwater LSP actuation. The LSP actuation resulted in the A Train ESW pump receiving a start signal, and the A motor-driven and the turbine-driven AFW pump suction supply valves receiving an actuation signal to transfer the suction supply from the normal source to the ESW system. Neither the motor-driven nor the turbine-driven auxiliary feedwater pumps started because they had been properly removed from service earlier in the outage. The A ESW pump was already running. No water was transferred from the ESW system to the AFW system since system tagging had been previously placed to isolate the two systems. The actuations were considered invalid because they were caused by opening breaker NK5409 which resulted in loss of power to the B ESFAS cabinet. The Senior Resident Inspector was notified. |
Where | |
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Callaway ![]() Missouri (NRC Region 4) | |
Reporting | |
10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
Time - Person (Reporting Time:+1420 h59.167 days <br />8.452 weeks <br />1.945 months <br />) | |
Opened: | Steve Petzel 13:04 Jun 22, 2013 |
NRC Officer: | John Shoemaker |
Last Updated: | Jun 22, 2013 |
49141 - NRC Website
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WEEKMONTHYEARENS 570912024-03-25T01:56:00025 March 2024 01:56:00
[Table view]10 CFR 50.73(a)(1), Submit an LER Invalid Actuation of Automatic Turbine Driven Auxiliary Feedwater Pump ENS 559722022-05-02T04:05:0002 May 2022 04:05:00 Other Unspec Reqmnt, 10 CFR 50.73(a)(1), Submit an LER Invalid Specified System Actuation ENS 491412013-04-24T09:04:00024 April 2013 09:04:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephone Notification for an Invalid Specified System Actuation ENS 491032013-04-11T06:28:00011 April 2013 06:28:00 10 CFR 50.73(a)(1), Submit an LER 60-Day Optional Telephone Notification for an Invalid Specified System Actuation 2024-03-25T01:56:00 | |