Management of low level wastes at Rokkasho reprocessing plant

Full text: At Rokkasho Reprocessing Plant (RRP), after start-up of the commercial operation, radioactive wastes will be generated. Wastes generated from a reprocessing plant generally consist of many kinds of characteristics in view of ''activity level'', ''nuclide composition'', ''chemical properties'', ''physical properties'', and so on. For stable operation of a reprocessing plant, we should treat, ''condition'' and ''dispose'' these wastes considering these wastes characteristics. To contribute to the nuclear fuel cycle project, it is important to evaluate technologies such as, ''Treatment'', ''Conditioning'' and ''Final Disposal'', not only for technical but also for economical aspects. Considering the final disposal in the future, the basic policy in ''Treatment'' and ''Conditioning'' at RRP is shown below: Recover and reuse chemicals (such as nitric acid and TBP, etc.) in plant; Radioactive waste shall be divided, classified and managed according to activity level, nuclide composition, the radiation level, its physical properties, chemical properties, etc.; Treat them based on ''classification'' management with proper combination; Condition them as intermediate forms in order to keep flexibility in the future disposal method; Original volume of annually generated wastes at RRP is estimated as 5600m3 except highly radioactive vitrified waste, and these wastes shall be treated in the following units, which are now under commisioning, in order to reduce and stabilize wastes. Low-level concentrated liquid waste to be treated with a ''Drying and peptization'' unit; Spent solvent to be treated with a ''Pyrolysis and hydrothermal solidification'' unit; Relatively low-level non-alfa flammable wastes to be treated with a ''Incineration and hydrothermal solidification'' unit; CB/BP (Channel Box and Burnable Poison) to be processed with a ''Cutting'' unit; Other wastes to be kept as their generated state with a ''Intermediate storage''. As a result of these treatments, the volume of wastes can be decreased down to about 40% of the amount of original generation. Japan Nuclear Fuel Limited is also planning to establish a facility to cope with final conditioning of waste. The final conditioning facility is planning to adopt the following main functions: Compression of hulls and end-pieces; Incineration of relatively highly flammable and less-flammable wastes and spent resin; Melting of non-flammable wastes; Cementation of all wastes except hulls and end-pieces. With these proved conditioning methods, the final condition of wastes can be suitable for the disposal concept. The volume of all low-level wastes generated at RRP can be decreased to 1/5 or less when the planned facility is operated. A great volume reduction is possible for wastes generated at RRP using current technologies; moreover, we should consider the following items: Decrease of original waste; Further volume reduction; Rationalization of the disposal concept due to the proper classification of waste