5 décembre 2017
Les contrôles de radiations de la ligne de vapeur principale ont été perdus ainsi que les deux voies de contrôle de radioactivité de l’eau. Avec la perte de ces contrôles au niveau de la vapeur, toutes les actions à mener d’urgence suite à la rupture d’un générateur de vapeur ne pourraient être ni évaluées ni conduites. Avec la perte des données radioactives de la station des eaux, toutes les mesures d’urgence à prendre en cas de rejets radioactifs dans l’environnement ne pourraient également être ni évaluées ni conduites. Des mesures compensatoires ont été mises en place comme des contrôles sur les conduites principales de vapeur avec un compteur Geiger ainsi que des contrôles chimiques sur les eaux dont les résultats sont transmis à la salle de commande. Lors de la maintenance d’un ordinateur commun aux deux réacteurs, de manière inexpliquée, d’autres ordinateurs sont tombés.
Type : PWR - Puissance : n° 1 : 3 612 MWth - n°2 : 3 458 MWth - Première divergence n°1 : 4 / 1990 - n° 2 : 3 / 1993 -
Available in english only
Event Number : 53105
Facility : COMANCHE PEAK - State : TX -
Unit : [1] [2] [ ] - RX Type : [1] W-4-LP,[2] W-4-LP
Event Date : 12/05/2017 - Event Time : 20:00 [CST]
Emergency Class : NON EMERGENCY 10 CFR Section : 50.72(b)(3)(xiii) - LOSS COMM/ASMT/RESPONSE
Initial PWR Current PWR 1 N Y 100 Power Operation 100 Power Operation 2 N Y 100 Power Operation 100 Power Operation
Event Text
UNPLANNED LOSS OF MULTIPLE RADIATION MONITORS DURING MAINTENANCE
"At 2000 (CST), Comanche Peak experienced a failure of SCADA B of the PC11 Radiation Monitor System. This failure caused a loss of Unit 1 Main Steam Line 1-01 and 1-03 Radiation Monitors (1-RE-2325 and 1-RE-2327) and Train A and Train B Station Service Water Radiation Monitors (1-RE-4269 and 1-RE-4270). With the Main Steam Line Radiation Monitors nonfunctional, all of the emergency action levels for a steam generator tube rupture in steam generators 1-01 and 1-03 could neither be evaluated nor monitored. With the Station Service Water Radiation Monitors non-functional, all of the emergency action levels for a radioactive release through station service water could neither be evaluated nor monitored. This unplanned condition is reportable as a loss of assessment capability per 10 CFR 50.72(b)(3)(xiii).
"Comanche Peak Nuclear Power Plant (CPNPP) has assurance of steam generator integrity, reactor coolant system integrity, and fuel cladding integrity and there is a negligible safety significance to condition from a public health and safety perspective. Additionally, compensatory measures are in place to assure adequate monitoring capability is available to implement the CPNPP emergency plan in the unlikely event of challenges to the steam generator, reactor coolant system, or the fuel cladding. Until these radiation monitors were restored, Operations implemented compensatory measures to monitor the Condenser Off Gas Radiation Monitor for early signs of a steam generator tube leak/rupture and Radiation Technicians were briefed on taking local readings with a Geiger-Mueller tube on the Main Steam Lines. Chemistry Technicians were performing hourly samples of Station Service Water and reporting results to the Control Room.
"Corrective actions were pursued to restore the non-functional radiation monitors back to service. Those actions are complete and all radiation monitors have been restored to service.
"The NRC Resident Inspector has been notified."
PC11 is a computer common to both Units. The failure happened during radiation monitor maintenance to a single monitor, which unexpectedly affected multiple monitors.
https://www.nrc.gov/reading-rm/doc-collections/event-status/event/2017/20171206en.html
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