INES-event
INES 2

Non-respect of a safety-criticality requirement at AREVA NC Melox facility (Marcoule)

On 3 March 2009, during an exceptional operation a criticality related event occurred in the laboratory of AREVA Melox facility (MOX plant). A first team of workers introduced a fissile sample in a mass controlled workstation. This sample was not counted prior to its introduction as it should, this due to the use of an unsuitable procedure. During the team's break, a second group of workers introduced a second fissile sample exceeding a safety physical mass limit. The second introduction was in compliance with procedure. When the first sample was weighted and counted no alarm was emitted. The excess thus remained undetected until the next day when the workers manually checked this workstation as they usually do. The analysis reveals the inadequacy of the introduction procedure that applies to fuel sample coming from other facilities and a failure of the software for fissile material counting dedicated to the mass management of criticality concerned workstations.ASN performed on 6th March 2009 a reactive inspection in order to evaluate causes of this incident and its impact on the facility safety. ASN will ensure that the operator will draw the necessary experience feedback concerning this incident. In particular the operator will have to complete its documentary framework, modify its software related to fissile material counting and improve traceability of operators’ actions. ASN is implementing a follow-up of the facility focused on the prevention of criticality risk.

Location: MELOX Fuel process plant
Event date: Tue, 03-03-2009
Nuclear event report
Legenda & explanation