[en] The Japan Atomic Energy Research Insitute (JAERI) is carrying out research on partitioning and transmutation under the national long-term R and D program, called the OMEGA program. The program aims at development of the technology to improve efficiency and safety in the final disposal of radioactive waste. Conceptual design studies are being made on hybrid systems driven by intense proton linacs as promising options for dedicated transmutation devices. The system burns minor actinides efficiency in hard neutron spectrum and high neutron flux. A 30-60 MW experimental integrated system and a 7 MW high-power target facility are proposed to construct under a plan of an accelerator-based multi-purpose research complex called the Neutron Science Project. The experiments will demonstrate the technical feasibility of the hybrid system and the capability of minor actinide transmutation. (Author) 7 refs

No abstract available

[en] We have investigated in detail the structures of nano-sized sphere-like platinum particles self-assembled on and in chemical-vapor-deposited (CVD) diamond. The Pt particles were transformed from Pt thin films deposited on various diamond substrates after hydrogen microwave plasma irradiation or CVD diamond overgrowth. This structural change of the Pt films was found to be a kind of hydrogen catalytic effect and to depend on the Pt film thickness and the treatment temperature. The average diameter of the self-assembled Pt particles was well controlled by changing thickness of the Pt film deposited on the diamond substrate. Especially, the Pt particles with diameters less than 10 nm were analyzed by means of a transmission electron microscope, and were found to be single-crystalline in structure. Furthermore, electron diffraction data of the Pt particles evidenced an expansion of the Pt lattice

[en] A new concept to improve the Doppler coefficient of metallic fuel liquid metal fast breeder reactor is proposed. This is accomplished by adding a moderating material to a metallic fuel assembly, so that the neutron spectrum becomes softer and the negative temperature coefficient are improved. The effects to the typical core parameters, such as Doppler coefficient, the sodium void reactivity and the reactor breeding ratio are investigated. The results show this concept improves temperature coefficients similar to those of mixed oxide core of the same size without much sacrificing the breeding ratio. (authors). 7 refs., 3 figs., 2 tabs

[en] Paper presents data on the efforts to investigate into the transmutation efficiency of minor actinides in terms of the subcritical reactor core controlled by a linear accelerator (the ADS System Design). The Pb-Bi liquid eutectics is considered to serve as a coolant and as a neutron source within the system. On the basis of the numerical parametric analysis of the multiplication factor evolution and of the reactor core reactivity, as well as, on the basis of choice of Pu initial load one offers the ADS transmutation system optimal configuration

[en] Two-dimensional (2-D) heterogeneity effects on cell-averaged cross sections and diffusion coefficients have been estimated. Both of the heterogeneity effects caused by the flux fine structure and the resonance shielding are taken into account. The accuracy of several 1-D cell models is assessed by comparing cell parameters obtained from 1-D and 2-D cell calculations. The 2-D cell heterogeneity effects on core performance parameters have been evaluated for the large fast critical assembly ZPPR-9. The Zebra CADENZA plate-pin experiments have been analyzed using the 2-D cell model, the usefulness of the 2-D cell calculation is discussed

[en] Research and development on transmutation of long-lived radioactive nuclides are being carried out with an emphasis placed on the dedicated accelerator-driven systems at the Japan Atomic Energy Research Institute (JAERI) under the Japanese long-term program for research and development on partitioning and transmutation technology (OMEGA Programme). The preliminary design of the sodium-cooled solid system has been developed as a reference system based on the current LMFBR technology. Concurrently with the study on the sodium-cooled system, we made a preliminary design study of lead-bismuth cooled system as an option. Transient responses of temperatures and stresses due to accelerator beam trips were evaluated for the fuel pin and the beam window of the proposed experimental facilities. (author)

[en] The accelerator-driven transmutation system has been studied at the Japan Atomic Energy Research Institute. This system is a hybrid system which consists of a high intensity accelerator, a spallation target and a subcritical core region. Nuclides in high-level waste to be transmuted are minor actinides and long-lived fission products which are loaded in subcritical core and blanket in ADS, respectively. The calculations of subcriticality and burnup swing by present evaluated nuclear data were performed to investigate the effect on the performance of ADS. To compare with the integrated experimental and calculational results, analyses of actinide samples irradiated in the Dounreay Prototype Fast Reactor are presented. Recent measurements for thermal neutron capture cross section which affect transmutation efficiency are shown compared with evaluated nuclear data for some long-lived fission products. (author)

No abstract available

[en] For a metallic fuel liquid metal fast breeder reactor, we studied a core concept for improving the Doppler coefficient and the sodium void reactivity without much sacrificing the breeding ratio and the burnup reactivity loss. In the concept, several ordinary fuel pins in all fuel assemblies of a core are substituted by pins containing only zirconium hydride (ZrH). A parametric survey for the ZrH fraction from about 1 to about 5% was performed in this study to investigate the reactivity coefficients and the associated demerits in order to search the optimum fraction of ZrH. The metallic fuel core containing about 3% of ZrH showed the good results for all parameters. Following the parametric study, the effect of hydrogenous material in a metallic fuel core was experimentally confirmed. Doppler reactivity, sodium void reactivity and sample reactivity worths of plutonium and B₄C were measured in a series of critical experiment at FCA of JAERI. The experimental results showed that the hydrogenous material significantly improved the Doppler and the sodium void reactivities. Analysis of experimental results was performed to check the applicability of the present design codes for a fast reactor with hydrogenous materials