Management of Low Level Wastes at Rokkasho Reprocessing Plant

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1 Management of Low Level Wastes at Rokkasho Reprocessing Plant Noriyasu MORIYA, Eiji OCHI Reprocessing Plant Department, Reprocessing Business Division Japan Nuclear Fuel Limited, Rokkasho-mura, Kamikita-gun, Aomori-ken, Japan Tel , Fax , ABSTRACT: Generated wastes volume is estimated as 5,600m3 on the original design base at Rokkasho Reprocessing Plant (RRP) along with an annual operation. These wastes shall be treated in the waste treatment facility in order to reduce and stabilize waste. As a result, the volume of waste can be decreased up to about 40% of the amount of generation. JNFL is also planning to construct a facility to cope with final conditioning of waste and the most suitable disposal packages. The volume of all low-level wastes generated at RRP can be decreased to 1/5 or less. KEYWORDS: low level waste, treatment, condition, disposal. INTRODUCTION Japan Nuclear Fuel Limited (JNFL) will start the commercial operation of RRP on August After starting 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 the stable operation of a reprocessing plant, we should treat, condition and dispose these wastes, considering these wastes characteristics. Concerning the disposal concept of wastes, National Policy for TRU-containing wastes disposal, called TRU Report, was issued on March 2000 by the Atomic Energy Commission of Japan. This report states the following disposal concept about TRU-containing wastes. Keeping safety by disposing of wastes in three different activity levels, Shallow Land Disposal, Mid-Depth Disposal and Deep Geological Disposal Disposal of these wastes shall be in these three categories according to radioactive nuclide concentration and radiation level to secure safety.. WASTE TREATMENT METHOD 1. Basic Policy in Treatment and Conditioning at RRP To contribute the nuclear fuel cycle program of Japan, it is important to evaluate technologies such as, Conditioning, and Final Disposal, not only for technical but also for economical aspects. Considering the final disposal in the future, the basic policy in Conditioning at RRP is shown below. Recover and reuse chemicals (such as nitric acid, TBP, etc) in the plant Radioactive waste shall be divided and managed according to activity level, nuclide composition, radiation level, physical properties, chemical properties, etc. Condition them as intermediate forms in order to keep flexibilities in the future disposal 2. Present Status Original volume of generated wastes at RRP is estimated as 5,600m3/year except highly radioactive vitrified waste, and these wastes shall be treated in the following units, which are now under test operation, in order to reduce and stabilize wastes. Low-level concentrated liquid waste to be treated with a Drying and pelletization unit Spent solvent to be treated with a Pyrolysis and hydrothermal solidification unit Relatively low-level and non-alfa flammable wastes to be treated with an Incineration and hydrothermal solidification unit Channel box and Burnable poison to be processed with a Cutting unit

2 Other wastes to be stored in their generated shapes with a Intermediate storage facility Less-Flammable ƒ Àƒ Á Spent Iodine Huls&End Charcoal Filter -Pieces Channelbox& Burnable Poison Liquid Waste 4% 0% 7% 2% 13% Non-Flammable ƒ 8% 1% 5% 5600m3 / year Non-Flammable ƒ Àƒ Á 15% Flammable ƒ Àƒ Á 3% 42% Flammable & Less-Flammable ƒ Fig.1 Volume rate of wastes generated in RRP Fig.2 Concentrated Low Active Liquid Waste Treatment system Fig.3 Incineration and Hydrothermal Solidification Treatment system As a result of these treatments, the volume of the wastes can be reduced up to about 40% of the amount of original generation Iodine Filter Volume (m3/year) Drying & Pelletization, NOx Recovery Incineration & Hydrothermal Solidification Intermediate Treatment Spent Charcoal Liquid Waste iƒ,ƒ Àƒ Á j Less-Flammable iƒ Àƒ Á j Flammable iƒ Àƒ Á j Flammable & Less-Flammable iƒ j Non-Flammable iƒ Àƒ Á j Non-Flammable iƒ j Channel Box & Burnable Poison Hulls & End-Pieces Raw Waste Intermediate Storage Fig.4 Reduction Effect Waste Management (Compare with Raw Waste to Intermediate Storage)

3 3. Future Concept JNFL is also planning to construct a facility to cope with final conditioning of wastes. Followings are considered by JNFL on designing conditioning processes for the final disposal. Radioactive waste shall be divided and managed according to activity level, nuclide composition, radiation level, physical properties, chemical properties, etc Adopting the well experienced technologies which have been already used in general industries for volume reduction. Adopting technologies to be established as domestic technologies. Receiving and conditioning wastes generated at the other fuel cycle facilities in Rokkasho site, such as MOX fuel fabrication facility. Concerning the last item mentioned above, authorization for receiving wastes of the other facilities is still remained as a pending problem. With considering the above items, the final conditioning facility is planned to adopt the following main processes. Compression of hulls and end-pieces Incineration of relatively high-level flammable and less-flammable wastes, and spent resin Melting of non-flammable wastes Cementation of all conditioned wastes except hulls and end-pieces With these proved conditioning methods, the final condition of wastes can be suitable for the disposal concept. The outlines of the main process are mentioned below. A. Compression of Hulls and End-pieces The requirements on hulls and end-pieces compression process are as follows. To keep the consistency between conditioned wastes from this process and relatively low level wastes which are to be sent back from foreign reprocessing facilities To satisfy the requirement for settlement in shielded cells in order to handle hulls and end-pieces, which are relatively highly radioactive. With total consideration of both the above items and the experience in France of hulls and end-pieces conditioning process, a uni-axial press was selected. In our process, hulls and end-pieces are placed in a capsule of 70kg ~ 90kg, and compressed together with a capsule. In the real scale experiment, it was confirmed that volume reduction rate at 1/4 ~1/5 could be obtained by this process. B. Incineration Relatively High-level Flammable and Less-Flammable Wastes and Spent Resin The requirements on incineration process are as follows. To incinerate less-flammable wastes, such as rubber and PVC without any problems. To satisfy the requirement for settlement in shielded cells in order to handle wastes, which are relatively highly radioactive. To keep the suitability for criticality safety control because of incineration of Pu contaminated wastes. With considering the above items, a rotary kiln type incinerator was selected, which was achievable both capacity and maintainability. In our process, wastes are supplied and incinerated continuously. In the real scale experiment, it was confirmed that volume reduction rate at 1/15 ~1/20 could be obtained by this process. C. Melting of Non-flammable Wastes

4 The requirements on melting process are as follows. To be able to obtain information about radionuclide concentration in melted wastes without direct sampling of them. To satisfy the requirement for settlement in shielded cells in order to handle wastes, which are relatively highly radioactive. With considering the above items, an in-can type high-frequency induction melting system was selected, which was adopted and experienced at NPPs in Japan, and was achievable on both capacity and maintainability. [1] In our process, it was confirmed that volume reduction rate at 1/4 ~1/5 could be obtained by this process in the real scale experiment.. RESULT AND DISCUSSION 1. Result The total volume of low-level wastes generated at RRP can be reduced to 1/5 or less when the planned facility is operated. This value is equivalent to 1.25 m 3 /tu-spent fuel. On the other hand, the volume of vitrified HLW waste is 0.18m 3 /tu-spent fuel. Consequently, the volume of waste generated at RRP is totally 1.37m 3 /tu-spent fuel. Volume (m3/year) EDryi ng & Pel l et i zat i on ENOx Recovery Incineration & Hydrothermal Solidification Intermediate Treatment 40 Melting Incineration Melting Final Conditioning Directly Disposal of Spent Fuel Iodine Filter Spent Charcoal Liquid Waste(α,βγ) Less-Flammable(βγ) Flammable(βγ) Flammable & Less-Flammable(α) Non-Flammable(βγ) Non-Flammable(α) Channel Box & Burnable Poison Hulls & End-Pieces High Level Waste Raw Waste Intermediate Disposal Package Directly Disposal Fig.8 Reduction Effect Waste Management Comparison between the Other Case With the view of waste volume generated, the comparison study between reprocessing case and the other case without reprocessing is carried out. On the history of waste generated at COGEMA in France, data are evaluated for only long-lived radionuclide. So it is not able to directly compare between French data and our estimation, but the volume reduction effect of waste conditioning can be said to be almost the same. Fig.9 Reduction Effect Waste Management by Cogema

5 On the other hand, waste volume generated at the once-through option is calculated to be 1.5m3/tU-spent fuel as high-level waste and 0.2m3/tU-spent fuel as intermediate level waste. Consequently the total volume of wastes at the once-through option is 1.7m3/tU-spent fuel. [2] From these comparison studies, waste volume generated from the reprocessing is not inferior to that from the once-through option.. CONCLUSIONS The total volume of low-level wastes generated at RRP can be reduced to 1/5 or less when the planed 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 wastes Further volume reduction Rationalization of the disposal concept due to the proper classification of waste From the viewpoint of the waste management, the nuclear fuel cycle including the reprocessing shall be materialized economically. REFERENCES 1. S. Yamazaki, et al., Development of Induction Melting System With Active Insulator for Radioactive Solid Waste, The 9 th International Conference on Radioactive Waste Management and Environmental Remediation, icem (2003) 2. Trends in the Nuclear Fuel Cycle Economic, Environmental and Social Aspects-, ISSN , p35 (2002)