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Journal Articles

Investigation of beam window structure for accelerator driven system with subcriticality adjustment rod

Sugawara, Takanori; Iwamoto, Hiroki; Tsujimoto, Kazufumi

NEA/NSC/R(2017)3, p.149 - 159, 2017/11

In this study, new beam window concept for accelerator-driven system (ADS) is investigated by changing the design condition. The most important factor for the beam window design is the proton beam current, and the design condition will be mitigated if the proton beam current will be reduced. To reduce the proton beam current, a subcriticality adjustment rod which was a B$$_{4}$$C control rod was employed and neutronics calculations were performed by ADS3D code. The results of the neutronics calculation indicated that the proton beam current was reduced from 20mA to 10mA by the installation of the subcriticality adjustment rods. Based on the mitigated calculation condition, the investigation of the beam window was performed by the particle transport analysis by PHITS code, the thermal hydraulics analysis by STAR-CCM+ code and the structural analysis by ANSYS code. Through these coupled analyses, more feasible beam window concept which was the hemispherical shape, the outer diameter = 470mm, the thickness at the top = 4.0mm and factor of safety =12, was presented.

Journal Articles

Research and development on pyrochemical treatment of spent nitride fuels for MA transmutation in JAEA

Hayashi, Hirokazu; Sato, Takumi; Shibata, Hiroki; Tsubata, Yasuhiro

NEA/NSC/R(2017)3, p.427 - 432, 2017/11

Transmutation of long-lived radioactive nuclides including minor actinides (MA: Np, Am, Cm) has been studied in Japan Atomic Energy Agency (JAEA). Pb-Bi cooled sub-critical accelerator-driven system (ADS) is regarded as one of the powerful tools for transmutation of MA under the double strata fuel cycle concept. Uranium-free MA-Pu nitride fuel was chosen as the first candidate for MA transmutation. Reprocessing of spent ADS fuel and reusing MA recovered from the spent ADS fuels is necessary to improve the transmutation ratio. A pyrochemical process has been proposed as the first candidate for reprocessing of the spent nitride fuel for MA transmutation, because this technique has some advantages over aqueous process, such as the resistance to radiation damage, which is an important issue for the fuels containing large amounts of highly radioactive MA, and feasibility for recovering expensive N-15 in the spent fuels to be reused. This paper overviews the current status of the technology development, including our recent study. Development of the anode suitable for electro-refining of nitride fuels and that of the apparatus for renitridation of the metals recovered in Cd cathode for 100g-Cd scale cold tests are main topics. Evaluation of the batch sizes of each process, which is necessary for estimating the scale of the engineering-apparatus, with considering the decay heat of MA and FP, will also be introduced.

Journal Articles

Fabrication and short-term irradiation behaviour of Am-bearing MOX fuels

Kihara, Yoshiyuki; Tanaka, Kosuke; Koyama, Shinichi; Yoshimochi, Hiroshi; Seki, Takayuki; Katsuyama, Kozo

NEA/NSC/R(2017)3, p.341 - 350, 2017/11

In order to investigate the effect of the addition of americium to MOX fuels on the irradiation behaviour, the "Am-1" program is being conducted at the JAEA. The Am-1 program consists of two short-term irradiation tests of 10-min and 24-h irradiation periods, and a steady-state irradiation test. The short-term irradiation tests and their post irradiation examinations (PIEs) have been successfully completed. To date, the data for PIE of the Am-MOX fuels focused on the microstructural evolution and redistribution behaviour of Am at the initial stage of irradiation have been obtained and reported. In this paper, the results obtained from the Am-1 program are reviewed and detailed descriptions of the fabrication and inspection techniques for the Am-MOX fuels prepared for the program are provided. PIE data for the Am-MOX fuels at the initial stage of irradiation have been accumulated. In this paper, unpublished PIE data for the Am-MOX fuels are also presented.

Journal Articles

Effects of $$gamma$$ irradiation on the adsorption characteristics of xerogel microcapsules

Onishi, Takashi; Tanaka, Kosuke; Koyama, Shinichi; Ou, L. Y.*; Mimura, Hitoshi*

NEA/NSC/R(2017)3, p.463 - 469, 2017/11

no abstracts in English

Oral presentation

Technological investigation of the simplified MA-bearing fuel fabrication process for fast reactors and accelerator driven systems

Yamada, Yoshikazu; Kawaguchi, Koichi; Segawa, Tomoomi; Matsumura, Tatsuro; Kato, Masato

no journal, , 

Researchers at Japan Atomic Energy Agency (JAEA) have proposed the transmutation of minor actinides (MAs) by both fast reactors (FRs) and accelerator driven systems (ADSs) as a way to contribute significantly to the reduction of the volume and the potential radiotoxicity of radioactive wastes. Pu-U mixed oxide with small amount of MA is adopted as fuel of FRs, while U-free nitride and mixed oxide of MA, Pu and inert element are candidates for fuel of ADSs. JAEA researchers have also studied the simplified MOX fuel fabrication process to decrease the fabrication cost. This report describes a technological investigation of the simplified MA-bearing fuel fabrication process that prepares fuel suitable for both FRs and ADSs. Furthermore, this report includes an analysis of the feasibility of fabricating MA macro-dispersion pellets and MA micro-dispersion pellets for ADSs by using the simplified MOX fabrication process. The flowabilities of both de-nitrated raw powders were improved with the tumbling granulator, and the Carr flowability index was more than 70 for both. The green pellets had no defects in their appearance such as cracks. The CeO$$_{2}$$ particles were dispersed homogeneously in both macro-dispersion and micro-dispersion pellets. As a result, it was judged that the simplified MOX fuel fabrication process is applicable to fabrication of MOX pellets for ADSs as well as FRs.

Oral presentation

Alpha-ray degradation of CMPO adsorbents for the extraction chromatography

Watanabe, So; Takeuchi, Masayuki; Sano, Yuichi; Ishigami, Ryoya*

no journal, , 

Oral presentation

Review of research activities on partitioning and transmutation in Japan

Tsujimoto, Kazufumi

no journal, , 

The Government of Japan periodically formulates the Basic Energy Plan in accordance with an article in the Basic Act on Energy Policy that entered into force in 2002. The latest version, called the Strategic Energy Plan, was issued in April, 2014. The largest change from the previous versions must be the accident of the Fukushima Daiichi Nuclear Power Plant. In spite of the accident, the Plan defines the nuclear power as an important base-load power source as a low carbon and quasi-domestic energy source, contributing to stability of energy supply-demand structure, on major premise of ensuring of its safety. The Plan puts emphasis on the importance of activities to resolve the challenge of how to manage and dispose of spent fuel, as well as the Fukushima restoration, safety operation of nuclear plants, and public acceptance. As for the P&T technology, the Government will promote technology development on volume reduction and mitigation of degree of harmfulness of radioactive waste. Specifically, development of technologies for decreasing the radiation dose remaining in radioactive waste over a long period of time and enhancing the safety of processing and disposal of radioactive waste, including nuclear transmutation technology using fast reactors and accelerators, will be promoted by utilizing global networks for cooperation. Based on this new Strategic Energy Plan, research and development (R&D) on P&T are being accelerated in Japan. The Japan Atomic Energy Agency (JAEA) has been continuously implementing R&D on P&T technology to reduce the burden of the backend of the nuclear fuel cycle. The R&D on P&T in JAEA are basing on two kinds of concepts: one is the homogeneous recycling of minor actinide (MA) in fast reactors and the other is the dedicated MA transmutation, so-called double-strata strategy, using an accelerator-driven system (ADS). In this work, recent R&D activities based on these policies are briefly shown.

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