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Characterisation of the content of a radioactive waste drum : example of techniques used in France for plutonium measurement



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Pierre Funk, Bruno Autrusson.- CEG Workshop on Methods and Techniques for radioactive waste management applicable for remediation of isolated nuclear sites, 26-28 mai 2004 à Petten, Pays-Bas

Type de document > *Congrès/colloque

Mots clés > déchets radioactifs, mesures non destructives, plutonium

Unité de recherche > IRSN/DEND/SATE/L2MC

Auteurs > AUTRUSSON Bruno, FUNK Pierre

Date de publication > 26/05/2004


French ministerial directive of June 1988 gives the technical conditions for control and accountancy of nuclear materials contained in solid waste. As far as the nuclear materials follow-up is concerned, this text states that any nuclear material (plutonium or high enriched uranium) declared as waste, should be characterized. For other materials, best estimates are allowed. Reversibility possibility (from waste to usable material) was not considered.
It is the operator's responsability to declare as "waste" a nuclear material whose use is no longer economically profitable, generally due to low concentration of those materials. It is worth pointing out that the French regulation considers nuclear materials all along the fuel cycle (excluding ores) up to waste disposal with the adapted regime for waste mentioned above. That means that, for instance, uranium ores with a uranium concentration level of 1% currently met is not taken into account. That means also that nuclear materials in similar concentration could be eligible to be treated as waste but possibly also to be exempted from french domestic safeguards. The experience gained from the French safeguards inspections shows a variety of "waste" from scraped materials to contaminated items, especially in facilities under dismantling. Setting concentration levels could help to reduce those discrepancies and either to define a safeguards termination for those materials or to harmonize what could be labeled as waste in different facilities. Since precise quantification of nuclear materials in waste poses some problems, operators are often tempted to overestimate the nuclear material content of waste drums following basic criticality safety rules. This procedure is highly prejudicial for control and accountancy purposes since it results in biased nuclear materials balance and the obvious consequence that it is impossible to conclude on a possible loss or diversion of nuclear materials by the only analysis of the facility material balance. This is due to the fact that quantities that are shipped out of the facility are effectively smaller than those reported. This trend observed in the operator's behaviour reaches some limit for economical reasons since each waste drum should not exceed an activity limit (due to repository specifications in case of disposal), which corresponds to a nuclear materials mass limit.
The Nuclear Defense Expertise Division (IRSN) of the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) as the technical support of the French Competent Authority for NMPC&A has shown the need to improve the traceability of nuclear materials in wastes and to perform more precise physical measurements despite low concentration in wastes of elements under French domestic safeguards. IRSN has developed, for inspections purposes, original and complementary methods for the measurement of plutonium and uranium in waste drums. This paper describes the principles of these devices. It also addresses the possibility to use them for the characterization of other radioactive material. In a second part, it addresses a summary of the different kind of waste and measurement systems used in the French nuclear industry.