NUKEM Technologies was contracted to supply a dry, automated drum belt (tumbling) Abrasive Blasting Unit (ABU) to the Joint Research Centre of the European Commission in Ispra, Italy. The ABU was installed in the centralised radioactive waste management area of the JRC-Ispra site in Italy. The unit is to be employed for the decontamination to clearance levels of slightly contaminated metal components and, where practical, concrete or heavy concrete (density ∼3200 kg/m3) blocks arising from the dismantling of nuclear facilities. The presentation is based on the successful construction and installation of the ABU at the JRC Ispra site. Among the several possibilities of adapting conventional abrasive units to nuclear applications, an automatic tumbling machine was preferred, due to the larger output and (mainly) for the ease of operation, with minimum direct handling of contaminated material by operators, thus satisfying the ALARA principle. Consideration was also given to Belgoprocess’ successful experience with a predecessor, similar unit. After adequate size reduction batches of up to about 800 kg of material to be decontaminated are automatically introduced into the blasting chamber. Pieces between 100 mm and 800 mm long, between 100 mm and 500 mm wide and between 5 mm and 300 mm high can be effectively treated in the unit, the maximum weight of a single piece being limited to 100 kg. Short lengths of pipe may be included; the final dimensions of pipe to be decontaminated will be established during the nuclear commissioning tests. Other components with hard-to-reach surfaces may also be included. The content of the chamber is tumbled by two bladed drums, while sharp steel grit is sprayed onto the contaminated components, thus removing the surface layer including any contamination. From experience, 30 minutes of treatment is sufficient to remove contamination to levels below expected clearance levels for most materials. The decontaminated components are removed from the blasting chamber automatically and collected in skips. Dust and grit are led to a series of separators; the grit gets recycled to the blasting chamber, cleaned off contaminants such as paint are fed to collection bins, and the dust is bagged into waste drums. Airflow through the whole system cleans the decontaminated components, transports the dust to the collecting area, and acts as a dynamic barrier to limit risks of contamination of the surrounding areas. Prior to release back into the room, the air is filtered in a series of automatically cleaned filters, followed by HEPA filters. The whole facility is operated in an automatic mode: the operators are only required to place drums or pallets of contaminated material onto the feeder, and remove skips of decontaminated material and drums of secondary waste such as dust. The presentation will describe the system and potential applications in the nuclear industry in detail.

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