'CRITICALITY EVENTS' DATABASE FOR FUEL CYCLE FACILITIES IN SUPPORT OF THE IRSN NUCLEAR CRITICALITY SAFETY GUIDE

摘要

IRSN has developed a database gathering the events which have affected the safety of French fuel cycle facilities (from conversion to waste storage, laboratories and experimental facilities, facilities under dismantling and decommissioning). Among all the recorded events, it is possible to extract in particular those impacting the criticality safety. In order to extend the analysis of these events, the IRSN criticality safety department has developed a specific database dedicated to criticality risks. The "criticality events" database is continuously updated on the basis of the declared events and their analysis by engineers from the criticality safety department. At this time, about 380 events (on 540 identified since 1980) are described in details in this database. Thus, the number of events in facilities can be between 1 and 75. It is possible to establish a link, as a feedback, between the "criticality events" database and the sequences of events identified in the IRSN nuclear criticality safety guide. Indeed, the purpose of this guide is to be a support for criticality safety analysis or assessment. The guide is in the form of diagrams and gives advice to perform an assessment of criticality risks for each criticality control mode and for the reference fissile medium. Thus, the guide presents the parameters to be considered in the analysis and the typical sequences (written in the form of questions) related to the most current failures to be investigated. With the objective of being able to illustrate the nuclear criticality safety guide, it was decided to select the events of the database which are representative of the sequences. Thus, 70 sequences have been illustrated up to now by one or several events analyzed in the "criticality events" database. Furthermore, this action allows "extending" the nuclear criticality safety guide with sequences which had not yet been identified (when an event cannot illustrate a failure listed in the diagrams). This paper will describe the approach used to build the "criticality events" database, the criteria used to classify events and the link with the IRSN nuclear criticality safety guide.