Nuclear fuel cycle facilities11,12

Treatment of the gaseous waste from nuclear fuel cycle facilities removes aerial radioactive particles and gaseous radioactive nuclides before dis­charge of the gaseous effluent into the environment. In reprocessing plants, the gaseous waste is filtered through scrubbers, Ag-zeolite/Ag-silica-gel filters for iodine and HEPA filters, and then discharged through a stack after radioactivity measurement to ensure it is below regulatory limits. In MOX fuel fabrication plants, only aerial radioactive particles are generated. The off-gas is passed through HEPA filters, and discharged through a stack after measuring radioactivity.

Treatment of the liquid waste from reprocessing plants removes radioac­tivity in controlled liquid discharges and eliminates process effluents. The liquid waste treatment system is composed typically of the high active liquid subsystem, the intermediate active liquid subsystem, the low active liquid subsystem, the solidification subsystem and the solvent waste subsystem. The high active liquid subsystem collects and processes typically raffinate from the separation/extraction process. This waste is concentrated by evap­oration, vitrified and stored in a dedicated interim facility.

The intermediate active liquid subsystem collects and processes effluents from the acid recovery process, the solvent washing process, the off-gas scrubber, etc. This waste is concentrated by evaporation, and then the distil­late is fed to the low active liquid subsystem.

The low active liquid subsystem collects and processes floor drain liquids, the detergent waste, etc. These wastes are distilled, then filtered and dis­charged into the ocean after activity measurement. The concentrated waste is fed to the solidification subsystem.

The solidification subsystem collects and processes the concentrated wastes from the intermediate active liquid subsystem and the low active liquid subsystem. These wastes are adjusted to appropriate pH and concen­trated by flocculation/ultrafiltration, and then solidified with cement in the Tokai reprocessing plant of the JAEA Tokai Research and Development Center. In the spent fuel reprocessing plant in Rokkasho village (Rokkasho reprocessing plant), these wastes are dried with a film evaporator and pel­letized with a granulator. The processed solid wastes are stored in the facilities.

The solvent waste subsystem collects and processes waste solvent from the solvent washing process. This waste is solidified with epoxy resin at Tokai and hydrothermally solidified after pyrolysis at Rokkasho.

Treatment of the solid waste is implemented with the aim of volume reduction for storage, because a disposal facility is not yet available in Japan for TRU waste. The combustible wastes are incinerated, and the incinerated ash is placed in 200 L drums for storage. The non-combustible wastes are placed directly in appropriate containers, and stored at the facilities. In Tokai MOX fuel fabrication plant, plastics and polyvinyl chloride (PVC) are also incinerated in a dedicated incinerator.

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