WDC: Advanced System for Characterization of Alpha-Bearing Waste Contained in 200L and 400L Drums: Performances and Lessons Learned From the First Industrial Measurement Campaigns

The Waste Drum Characterization installation was originally developed for the assay of alpha-bearing waste in standard 200 l (55 gallons) drums during the dismantling operations of the Siemens mixed-oxide (MOX) facility in Hanau (Germany). That installation was validated and qualified by the German authorities, its main performances being: - Counting efficiency for coincident neutrons: app. 1%; - Lowest Limit of Detection (LLD): 75 mg ²⁴⁰Pu_eq; - Pu content per drum: up to 100 g tot. (35 g ²⁴⁰Pu_eq); - Measurement duration: app. 20 minutes. The success of this system, a passive neutron coincidence counter combined with a high resolution gamma spectrometer, led to the radiological characterization and qualification of about 1,700 drums during the period 2001 – 2004. In 2005, after completion of the dismantling operations of the Siemens MOX facility, Tecnubel took over the WDC installation which could be used in the frame of the future dismantling of the Belgonucleaire’s MOX plant in Dessel (Belgium), which can be comparable to the Siemen’s one. This second (and new) life for the WDC means that it must be rigorously retested and validated against the Belgian authorities requirements. Furthermore, and additionally to the future use in the Belgonucleaire’s facility, Tecnubel was faced with new challenges, namely: - Assay of 400 l drums together with the 200 l packages; - Determination of the real LLD taking into account the background in different Belgian nuclear facilities, the determination of a value of ∼5 mg ²⁴⁰Pu_eq being an objective; - Assay of mixed alpha/beta-gamma wastes; - Transportability of the WDC from one plant to another; - Assistance to different nuclear operators for the licensing of the WDC for their own waste types. This paper describes the installation itself and its performances, presents the difficulties encountered during the new challenge and the results of the performed revalidation tests; it gives the perspectives and objectives on short time as well.