Decommissioning of Buildings 105X and 122X at Belgoprocess

The Eurochemic reprocessing plant was built between 1960 and 1966 and operated from 1966 until the end of 1974. During these eight years of active operation, Eurochemic reprocessed 181.5 t of natural and slightly enriched uranium fuels (less than 4.5% initial ²³⁵U enrichment) from various experimental and power reactors, and 30.6 t high enriched uranium fuels from testing reactors, generating approximately 50 m³ of high-level liquid waste from power reactor fuels (LEWC, low enriched waste concentrate ) and 850 m³ from research reactor fuels (HEWC, high enriched waste concentrate). As a result of reprocessing and cleaning operations (1975–1981), generated intermediate and high level wastes were put into temporary storage, pending the availability of appropriate treatment, conditioning and storage facilities. Immediately after LEWC and HEWC vitrification, the corresponding storage vessels were rinsed and decontaminated. The rinsing and decontamination program started in April 1986 and was interrupted between September 1987 and July 1989 in view of possibly reusing the vessels for storage of similar HLLW (high level liquid waste) solutions. Because the storage building itself was not aircraft crash resistant, it was decided not to use the storage vessels anymore and to proceed the decontamination with more aggressive chemicals. Due to this time gap however, and especially because vitrification came to an end in September 1991, a considerable volume of decontamination liquids was produced after this time and stored, pending the availability of the bituminization installation. In 2005 and 2006 a research program was performed. For both buildings and vessels images and samples were collected and dose rate measurements were executed. The paper presents an overview of the different studies that were indispensable in order to be able to select the most appropriate decommissioning strategy.