Methods of disposal with institutional control include near-surface disposal without artificial barriers, near-surface disposal with artificial barriers and sub-surface disposal with artificial barriers. Near-surface disposal with arti­ficial barriers is already used for LLW generated in commercial nuclear reactor facilities. Near-surface disposal without artificial barriers is being partly implemented while the reactor operators improve safety regulations on the remainder of the wastes. Operating entities are conducting studies and tests on sub-surface disposal with artificial barriers. Based on the results, it will be necessary to discuss the establishment of the framework, including safety regulations.

The current status of management of other LLW is described in Section 23.1.2.

High-level radioactive waste

In line with the Specified Radioactive Waste Final Disposal Act, final dis­posal facilities are planned for the geological disposal of HLW and are scheduled to start operation in the 2030s through the following three-step selection process: selection of preliminary investigation areas, selection of detailed investigation areas, and selection of the final disposal facility areas. When local governments wish to volunteer for ‘areas to be investigated as to the feasibility of constructing final repository of HLW’, it is important that the implementor (NUMO), the government and the utility companies give sufficient understanding and awareness to the local residents about the advantages and disadvantages of the final repository and various sectors of the local community, including local government. The government, research and development (R&D) institutions and NUMO, while giving due consid­eration to their own roles and in close partnership, are expected to consist­ently promote R&D into HLW geological disposal. NUMO is expected to safely implement the final HLW disposal project and systematically perform technical development to improve the economics and efficiency of the dis­posal activities. R&D institutions, led by the JAEA, through utilization of underground research facilities, continue to conduct research on under­ground geology, basic R&D towards improved reliability of geological disposal technology and safety assessment methods, and for safety regulations.

While being aware of overseas knowledge and experience, it is important to develop and maintain an advanced knowledge base that supports final repository projects and safety regulations, as well as to appropriately reflect it in NUMO’s final disposal projects. To this end, the government and R&D institutions work together to survey the entire Japanese waste management programme systematically and efficiently. R&D institutions such as JAEA, Radioactive Waste Management Funding and Research Center, etc., need to cooperate with the government and NUMO in activities to improve the understanding and awareness of society at large. Furthermore, it is neces­sary for the government to develop specific rules concerning safety regula­tions based on the progress of these R&D activities.

Geological disposal of radioactive wastes containing transuranium elements

Some LLW containing TRU elements needs to be disposed of geologically. If some TRU waste targeted for geological disposal can be buried together with HLW (co-disposed), the number of repository sites may be reduced, improving economic efficiency. Based on assessment of the influence of TRU and HLW co-disposal on the integrity of the disposal site, the govern­ment should then consider necessary measures, including the nature of an implementing body and its own involvement.

LLW from overseas reprocessing consigned by Japan will gradually be returned from France and the UK. French reprocessing firms suggest chang­ing the solidification method from embedding in bitumen to vitrification, while UK reprocessing companies will embed the LLW in cement for geo­logical or disposal with institutional control. In the latter case, the waste returned to Japan is HLW (vitrified waste) with equivalent levels of radio­activity to the LLW exported. In light of these suggestions, it is expected that the number of shipments can be reduced and storage facilities in Japan for LLW awaiting final disposal can be downsized. Thus, the government, in response to discussions with the operators, will assess the benefits of waste treatment by the new solidification methods, suggested by France, and of the conversion indexes of waste, as suggested by the UK. If these suggestions are found to be acceptable, the government should discuss the institutional issues.

Radioactive liquid and solid wastes from utilization of RI are exclusively collected and treated by the Japan Radioisotope Association. Organic liquid waste and flammable solid wastes are treated by incineration, and stored in suitable containers. Inflammable solid wastes are compressed with a compactor, and placed in 200 L drums.

Technological development

Development of treatment technology for liquid wastes is mainly aimed at solidification of the concentrated liquid waste to reduce the product volume ratio. Cementation technology was originally adopted while bituminization, plastic solidification with unsaturated polyester resin, and improved cemen­tation technologies were developed later. The latest solidification treatment adopts the dry-pelletizing method combining a film evaporator and a granu­lator. The resulting granules are mixed with Portland cement and solidified in 200 L drums. This method gives a high waste volume reduction compared to the early cementation method.

Technology development of solid waste treatment has largely focused on incineration technology and volume reduction technologies for miscellane­ous waste. Incineration for chlorine-containing materials including PVC using an incinerator with a water-cooled cylindrical chamber has been developed. This incinerator has an off-gas system as a countermeasure against dioxin. An incinerator with an ash melting system has also been developed with a high temperature chamber to burn and melt simultane­ously or an incinerator and a separate melting furnace. This type of incin­eration system can treat flammable and non-flammable materials producing slug granules with high volume reduction ratio.

For non-combustible wastes, super-compaction technology and melting technology have been developed. A super-compaction system with over 10 MN compressive force has been developed using a triaxial compressive or a uniaxial compressive machine with a drawing mould for direct encapsulation to 200 L storage drums. Both high-frequency induction or plasma heating furnaces are used in NPP for melting. The high-frequency induction furnaces use a disposable crucible, which can be placed directly in a 200 L drum. Some treatment technologies such as vitrification, steam reforming, etc., for iodine filters and ion-exchange resins are under development.

Treatment of the gaseous waste from research facilities is performed to remove radioactive particles before discharge into the environment. The off-gas from the ventilation system is passed through a HEPA filter, and then discharged through a stack after radioactivity measurement.

Small amounts of liquid waste are generated from chemical drains, floor drains and detergent waste. These wastes are treated to remove radionu­clides by flocculation or evaporation, and discharged into the environment. Pre-treatment such as neutralization is performed before treatment as needed.

In many small laboratories, solid wastes are placed in containers for storage without treatment. However, large institutes, in which many solid wastes are generated, treat the solid waste to reduce its volume for storage. The solid waste treatment system consists typically of pre-treatment, incin­eration and super-compaction. The pre-treatment is composed of cutting and segregation. Large wastes are cut into small pieces appropriate for compaction/packing. Solid wastes are sorted into combustible wastes and non-combustible wastes. The non-combustible wastes are further sorted into compressible and incompressible wastes. The combustible wastes are burned in excess air-type incinerators, and then stored. The compressive wastes are compressed with 20 MN force at the super-compactor. The waste compacts and incompressible wastes are placed in 200 L storage drums.

Treatment of the gaseous waste from enrichment plants removes fluoride and radioactive particles before discharge into the environment. The off-gas from centrifuges is typically filtered with NaF filters, alumina filters, and HEPA filters, and then discharged through a stack after radioactivity measurement.

In the enrichment plants, small amounts of liquid waste are generated from floor drainage and detergent wastes. These wastes are typically treated by flocculation using a flocculate agent such as polyaluminum chloride, and discharged into the environment.

Treatment of the solid waste is aimed at volume reduction for storage. Combustible wastes are incinerated, and then placed in 200 L storage drums. Incombustible wastes are placed directly in appropriate containers, and stored at the facilities.

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.

NPPs

Off-gas waste from NPPs contains mainly short-lived noble gas nuclides. Off-gas treatment is aimed at decay of short-lived nuclides and the removal of aerosol radionuclides. The off-gas treatment system consists of a hydro­gen recombiner unit, an activated charcoal retention unit and a filtration unit. The off-gas from the ventilation system is passed through the charcoal filter and the high efficiency particulates air (HEPA) filter to eliminate iodine and aerosol, respectively. The treated off-gas is discharged through a stack after verification that it is under the regulatory limit.

Treatment of the liquid waste from NPPs aims where possible at recycling in the plant system, removing the radioactivity in controlled liquid dis­charges and eliminating process effluents. The liquid waste treatment system in a BWR is composed of the low conductivity subsystem, the high conduc­tivity subsystem, the detergent waste subsystem, and the solidification sub­system. The liquid waste from processes in BWR is divided into the low conductivity effluent, which has relatively high purification, and the high conductivity effluent, which has relatively low purification. The low conductivity subsystem collects and processes liquid wastes typically from the equipment drains in the primary cooling system. This waste is filtered through a hollow fibre membrane for removal of insoluble material and demineralized by mixed ion exchange resin for removal of soluble chemi­cals, and then returned to condensate storage prior to further use as reactor coolant.

The high conductivity subsystem collects and processes liquid wastes from floor drains and effluents from regeneration of the resins. These wastes are concentrated by evaporation, and fed to the solidification subsystem. The distillate is demineralized on the mixed ion-exchange resin, and then returned to condensate storage or discharged to the ocean after verification under regulatory limit. The detergent subsystem collects and processes detergent waste from personnel hand-wash and laundry operations. These wastes are filtered, and then discharged to the ocean.

The solidification subsystem collects concentrated waste in a dedicated tank. This waste is mixed with cement or bitumen, and solidified in 200 L drums. The latest solidification subsystem adopts the dry-pelletizing method in which the concentrated waste is dried with a film evaporator, and dried powder mixed with binder is pelletized by a granulator. This method gives a high waste reduction volume compared to cementation/bituminization.

The liquid waste treatment system for PWR is similar to that for BWRs. PWR employs the recoverable effluent subsystem corresponding to the low conductivity subsystem of BWR. The recoverable effluent containing boric acid from the primary coolant system is demineralized, and then treated by evaporation to separate water and boric acid solutions for further use. Other subsystems are similar to those in BWRs.

Treatment of the solid waste from NPPs is aimed at stabilization and volume reduction for storage and conditioning prior to disposal. The solid waste treatment system is constructed typically of the pre-treatment sub­system, the incineration subsystem for combustible material, the compac­tion subsystem for incombustibles and the conditioning subsystem. The pre-treatment subsystem is composed usually of cutting and segregation. Large wastes are cut into small pieces appropriate for compaction/packing. Wastes are sorted into combustible, incombustible, compressible and incom­pressible wastes. Combustible wastes are burned typically in an excess air — type incinerator, and the incinerated ash is placed in a 200 L drum for storage. The compaction subsystem usually makes waste compacts of com­pressible and incombustible wastes with a compressing force between 50 kN and 3 MN. For higher reduction ratios, the super-compactor or the melting system is adopted in some NPPs. Waste compacts and incompressible wastes are placed in 200 L drums, and then filled with mortar in the conditioning subsystem for disposal. Figure 23.1 shows a typical treatment flow for BWR wastes.

A large portion of Japan ’ s radioactive waste (about 50%) is stored in the radioactive waste management facilities at the nuclear facilities. About 1,690 canisters of vitrified product and about 380 m3 of liquid waste as HLW are stored in the reprocessing facilities at Tokai and Rokkasho (interim storage facility of the glass canisters), as of the end of March 2010. About

267.0 m3 of LLW (excluding used steam generators, spent control rods, disused channel boxes) are stored in all nuclear facilities in Japan as of the end of March 2008. Storage volume of LLW is made up of approximately

144.0 m3 NPP waste, approximately 25,000 m3 TRU waste, approximately

9.0 m3 uranium waste, approximately 65,000 m3 research waste, and approximately 24,000 m3 RI waste6.

The JNFL near-surface disposal facility with engineered barrier systems in place at Rokkasho, Aomori-Ken is in operation for LLW from commer­cial NPPs and about 219,000 200 L drums have been disposed of as of the end of March 2010. About 1,670 tons of very low level wastes resulting from dismantling of the Japan Power Demonstration Reactor (JPDR) were dis­posed of at the near-surface disposal facility without engineered barriers at Tokai. This disposal facility has been on hold since October 1997.

23.2.1 Sources, types and classification of radioactive waste

In Japan, RAW is categorized as shown in Table 23.14 . In May 2007, the Nuclear Safety Commission of Japan (NSC) issued a document which pro­vides for upper bounds of concentration of radioactive elements in waste packages from power reactors and in TRU waste packages. The upper bounds of concentration of radioactive elements are so decided, that the

Classification Origin of Disposal method High-level radioactive waste Reprocessing plant Deep geological disposal (>300 m) Low-level radioactive waste Waste power reactor Relatively higher level Nuclear power plant Sub-surface disposal (50-100 m) Lower level Near-surface disposal with artificial barrier Very low level Near-surface disposal without artificial barrier TRU Reprocessing plant, MOX fuel fabrication plant Deep geological, sub-surface and near-surface disposal Uranium waste Enrichment plant, fuel fabrication plant and conversion and refining plant Not yet decided Rl and research waste Research facility Rl utilizing facility Deep geological, sub-surface and near-surface disposal

public exposure due to waste packages is well within the reference value, and that the upper bounds conform to the latest knowledge in the interna­tional community. Based on these concepts, disposal of RAW is categorized into Category 1 Waste disposal (geological disposal) and Category 2 Waste disposal (sub-surface disposal, near-surface disposal with artificial barrier and near-surface disposal without artificial barrier).

Concerning the waste that does not need to be dealt with as RAW, the NSC has studied the clearance level of radionuclide concentrations and its calculation method, by reference to the ICRP document (Pub. 46, 1985) and IAEA-TECDOC-855, respectively.

Radioactive waste (RAW) is generated by the research, development and utilization of nuclear energy at NPPs, nuclear fuel cycle facilities, test and research reactors, universities, institutes, and medical facilities, using accelera­tors, radioactive isotopes (RI) and nuclear fuel materials. It is essential that activities associated with research, development and utilization of nuclear energy also process and dispose of the RAW in such a way as to prevent any significant effects on the human environment now and in the future.

The generation that has enjoyed the convenience and benefits of nuclear energy assumes the responsibility to expend all efforts for safe disposal of RAW for the next generation. There are four principles for the treatment and disposal of RAW:

1. The liability of generators,

2. Minimization of radioactive waste,

3. Rational treatment and disposal,

4. Implementation based on mutual understanding with the people.

Under these principles, it is important to appropriately classify the wastes and treat and dispose of each classification safely based on the recognition that the wastes may include materials with characteristics that take an extraordinarily long time for the radioactivity to drop to insignificant levels2.

A near-surface disposal facility already operates for most of the low-level radioactive waste (LLW) generated at NPPs and is operated in Rokkasyo, Aomori-Ken by Japan Nuclear Fuel Limited (JNFL), as a private business, excluding part of the LLW. With regard to near-surface disposal of RI and research wastes, the Japan Atomic Energy Agency (JAEA) will conduct and promote disposal activity in cooperation with the government and other waste generators. As for the remaining LLW, JNFL plans to construct an intermediate depth disposal facility for NPPs and the Nuclear Waste Man­agement Organization of Japan (NUMO) will geologically dispose of transuranic (TRU) wastes. Funds from the owner of the reprocessing plant and mixed oxide (MOX) fuel fabricator, etc., have been accumulating via a levy to pay for geological disposal of TRU wastes since 2009. However, the implementing body for subsurface disposal of LLW, RI and research wastes has yet to be decided.

High-level radioactive waste (HLW), generated during reprocessing spent fuel (SF), is being vitrified and packaged prior to disposal in a geo­logical repository. Research and development for that purpose had been conducted mainly by what was the Power Reactor and Nuclear Fuel Devel­opment Corporation (PNC), which was restructured as the JAEA in October 2005 through the Japan Nuclear Cycle Development Institute. The government worked to develop a disposal system taking into consideration these policy guidelines and scientific evidence, and enacted the Specified Radioactive Waste Final Disposal Act in June 2000. NUMO was created in October 2002 as an implementing body for disposal, as specified in the Act. In December 2002, NUMO started ‘open solicitation’, which encouraged municipalities to consider investigating the suitability of their local area for developing a deep repository for HLW. Meanwhile, electric utilities and others have been accumulating funds for the disposal of HLW.