15 août 2014
Pendant l’opération de surveillance mensuelle du système de filtrage des gaz sur la voie B, le commutateur de sélection a été placé en mode manuel, ce qui a arrêté la voie A. Simultanément, l’afficheur de la voie B indiquait une défaillance de cette voie. Le débit aurait, pourtant, été de 6 920 m3/h (4 073 Standard Cubic Feet per Minute - SCFM). L’interruption a duré 2 min et a cessé lors du passage du commutateur dans sa position initiale.
Type Fukushima Daïchi (BWR Mark 1) - Puissance : 1 912 MWth - Première divergence : 03/1974
Available in english only.
Event Number : 50375
Facility : DUANE ARNOLD - State : IA Unit : [1] - RX Type : [1] GE-4
Event Date : 08/15/2014 - Event Time : 12:18 [
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(v)(C) - POT UNCNTRL RAD REL
Initial PWR : 95 % Current PWR : 95 %
Event Text
STANDBY GAS TREATMENT SYSTEM INOPERABLE
"On 8/15/2014 at 1218 CDT, the ’B’ Standby Gas Treatment (SBGT) System was undergoing its monthly surveillance testing. With the ’B’ fan running, as part of the surveillance, the ’A’ Standby Gas Treatment Mode Select Switch was taken to Manual. This renders the ’A’ SBGT subsystem inoperable. Almost simultaneously the ’B’ fan Flow Indicating Controller went blank and flashed an error message although indicated flow through the ’B’ train remained at 4073 SCFM. Based on the indication seen on ’B’ controller, regardless of flow, the ’B’ SBGT subsystem was also declared inoperable. In accordance with the surveillance the ’A’ SBGT mode switch was placed back in the AUTO position on 8/15/2014 at 1220 CDT, restoring that train to operability. The ’B’ SBGT was still considered inoperable based on its flow indicating controller being blank and flashing an error message. For a period of two minutes both SBGT subsystems were considered inoperable which is a condition that could have prevented the fulfillment of the safety function of SBGT system to control the release of radioactive material. This is considered a 8-hour reportable event per 50.72(b)(3)(v)(C) ’Any event or condition that at the time discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to control the release of radioactive material.’
"During the 2 minutes that ’A’ SBGT was in Manual, the ’B’ SBGT train maintained 4073 scfm train flow which is at the required flow rate per STP 3.6.4.3-01B. In addition, the ’A’ train could have been initiated manually at any time during that 2 minutes by the operator who was stationed at the panel performing the surveillance."
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2014/20140818en.html#en50375
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