INES-event
INES 2

Wrong positioning of fuel assemblies in the reactor vessel during refuelling operations

On April 2nd, 2001, during Dampierre nuclear power plant unit 4 refuelling, a shift in the refuelling sequence has led to a wrong position for 113 fuel elements within the reactor vessel. This event had no consequences on EDF staff's safety. The ASN has requested EDF to proceed to a detailed analysis of the event causes together with its potential consequences.
The first results of the analysis received by ASN showed that, in other conditions, inadequate position of fuel assemblies within the reactor vessel could have caused the beginning of a nuclear reaction. Under these conditions EDF analysis concluded that consequences would have remained limited for operators working in the vicinity.
The ASN requested supplementary studies that EDF submitted at the end of September 2001. They show that existing instrumentation would not have enabled to detect the power rise and thus to alert the operators before the nuclear reaction starts.
Consequently EDF has proposed that this event, provisionally rated last April at level 1 on INES severity scale, be uprated to the level 2.

Location: DAMPIERRE-4
Event date: Mon, 02-04-2001
Nuclear event report
Legenda & explanation