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Event Report Forms (ERFs) are filed to the IAEA. Sometimes there are multiple event reports, updating the rating, the event description. Here you only see the latest event report

ERF send date: Wed, 26-06-1991
ERF description: On Wednesday, 12 June, when the reactor was undergoing startup tests and was operating for the first time at 30% of full power, the automatic shutdown mechanism, actuated as the result of an incident in the conventional part of the facility, failed to function owing to non-availability of control circuit.
While a test was in progress, a failure in the conventional part of the facility reduced the steam generator feedwater flow below the required minimum, and this triggered the automatic shutdown request. The order was in fact given, but the control rods did not drop into the core because of missing wiring in the two lines of the shutdown system.
This incident had no safety consequences because the other protective actions taken brought the reactor into a safe state: the automatic shutdwon was not essential owing to the low power of the reactor, and the startup testing period thus had the advantage to detect the anomaly before the reactor was taken to higher power.
Furthermore, if other protective actions had not been sufficient to control the reactor. Other protection circuits would still have brought about the rod drop.
It is nevertheless true that one of the protective systems which was supposed to bring about automatic shutdown of the reactor was not operational. This situation gives rise to serious questions as to the origin of the fault - why the circuit was improperly connected - and the possibility of other anomalies.
An inspection visit in relation to this incident is to be carried out by DRIRE Alsace in the next few days.
A fresh startup of the reactor will not be authorized by the Nuclear Installations Safety Directorate until the operator's enquiries have enables him to guarantee full reliability of all the reactor's protection systems.
The Nuclear Installations Safety Directorate has also requested Electricite de France to carry out checks which should reveal any possible anomalies of the same kind in other French power reactors.
In view of the possibility of common mode failures on an important safety system, this incident is classified at Level 2 on INES.
BASIS FOR RATING:
DIFFICULTIES IN RATING:
ERF rating date: 01-06-1991
ERF contact person: Mr. J. Breuil
ERF address: 99 rue de Grenelle, F-75700 Paris, France
ERF affiliation: Ministere de l'industrie, Service central de surete des, installations nucleaires

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