[Research Activities]

    Partitioning and Transmutation (P&T) technology is to separate elements in high level radioactive waste discharged from the reprocessing plant depending on intended use to transmute long-lived nuclides to short-lived or stable ones. This technology aims at reducing the burden of high-level waste and to use the repository efficiently.

    In the Sector of Nuclear Science Research, JAEA, research and development of the technology for the transmutation of highly radioactive long-lived nuclides including minor actinides (MA: neptunium (Np), americium (Am), and curium (Cm)), using a dedicated Accelerator-Driven System (ADS) have been carried out.

    To transmute MA using ADS, neutrons produced by spallation of accelerated proton beam to metal target will be supplied successively to subcritical core to keep fission chain reactions of MA and other elements in the core.

    The core has fuel assemblies consists of bunches of fuel pins which have fuel pellets in the claddings like the fuels of other types of nuclear reactors. The composition and the chemical form of the fuel pellets containing MA elements should be appropriate for MA transmutation. Uranium-free MA nitride has been selected as the first candidate for the MA transmutation fuel.

    Previous feasibility study on transmutation system shows that only 20 % of MA in the fuel can be transmuted in one burning cycle of about 2 years. To increase the transmutation ratio, reprocessing of spent MA transmutation fuels and reuse of MA elements existing in the spent MA transmutation fuels are necessary. Therefore, fuel fabrication, transmutation, and reprocessing should be repeated in the MA transmutation fuel cycle as shown in Figure 1.

    “Research Group for MA Transmutation Fuel Cycle” has been carrying out research and development for the technology on reprocessing of spent MA transmutation fuel shown in Figure 2 to recover and reuse the MA in the spent fuels. One of our concerns is on pyrochemical treatment technology, in which molten salts and liquid metals are used as solvents; this technique is suitable for treatment of MA transmutation nitride fuels.

Research and Development to Reduce Radioactive Waste by Accelerator
- Current Status and Prospects for Partitioning and Transmutation Technology -

Atomic Energy Society of Japan,
Reprocessing and Recycle Technology Division
Text "Nuclear Fuel Cycle"
8-3 ADS Fuel Cycle (in Japanese)