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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: Thu, 02-07-1998
ERF description: On 11 June, while the reactor was operating, a spurious triggering of the containment spray system caused the primary pumps to cut out followed by a reactor emergency shutdown during which a control cluster remained jammed in the high position. In the event of an accident, the containment spray system sprays water into the reactor containment in order to reduce pressure and temperature and eliminate radioactive iodine.
A periodic test of the system, for reasons which have still not been clarified, caused a spurious triggering of the containment spray system and the issuing of command to isolate the containment which, in particular, caused an interruption in reactor coolant pump cooling and RCP cut-out. During the load reduction which preceded the reactor emergency shutdown one of the 65 control clusters remained jammed in the high position and did not drop even during the shutdown. The control clusters, which contain neutron-absorbing material, are one of the means the operator has at his disposal to control the nuclear reaction by inserting them into or withdrawing them from the core. Dropping the control clusters stops the nuclear reaction immediately. The operator then applied the relevant incident procedures in order to bring the reactor into a safe state. This incident had no effect on the environment.
The operator will keep the reactor shut down for investigations and any necessary maintenance. Authorization for restart of the reactor will be requested from the Director for the Safety of Nuclear Installations.
Since it involved several independent and simultaneous failures, including the failure of one safety system at a point when it was required to ensure reactor safety, this incident has been classified at level 2 on the INES by the Director for the safety of Nuclear Installations at the suggestion of the operator.
ERF rating date: 12-06-1998
ERF contact person: Mrs. V. Jacq
ERF address: Route du Panorama Robert Schum, France
ERF affiliation: DSIN

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