Sodium-cooled Fast Reactors

Ohshima, Hiroyuki; Morishita, Masaki*; Aizawa, Kosuke; Ando, Masanori; Ashida, Takashi; Chikazawa, Yoshitaka; Doda, Norihiro; Enuma, Yasuhiro; Ezure, Toshiki; Fukano, Yoshitaka; et al.

Sodium-cooled Fast Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.3, 631 Pages, 2022/07

https://shop.elsevier.com/books/sodium-cooled-fast-reactors/morishita/978-0-12-824076-2

This book is a collection of the past experience of design, construction, and operation of two reactors, the latest knowledge and technology for SFR designs, and the future prospects of SFR development in Japan. It is intended to provide the perspective and the relevant knowledge to enable readers to become more familiar with SFR technology.

Method to reduce long-lived fission products by nuclear transmutations with fast spectrum reactors

Chiba, Satoshi*; Wakabayashi, Toshio*; Tachi, Yoshiaki; Takaki, Naoyuki*; Terashima, Atsunori*; Okumura, Shin*; Yoshida, Tadashi*

Scientific Reports (Internet), 7(1), p.13961_1 - 13961_10, 2017/10

https://doi.org/10.1038/s41598-017-14319-7

Transmutation of long-lived fission products (LLFPs: Se, Zr, Tc, Pd, I, and Cs) into short-lived or non-radioactive nuclides by fast neutron spectrum reactors without isotope separation has been proposed as a solution to the problem of radioactive wastes disposal. Despite investigation of many methods, such transmutation remains technologically difficult. To establish an effective and efficient transmutation system, we propose a novel neutron moderator material, yttrium deuteride (YD), to soften the neutron spectrum leaking from the reactor core. Neutron energy spectra and effective half-lives of LLFPs, transmutation rates, and support ratios were evaluated with the continuous-energy Monte Carlo code MVP-II/MVP-BURN and the JENDL-4.0 cross section library. With the YD moderator in the radial blanket and shield regions, effective half-lives drastically decreased from 10 to 10 years and the support ratios reached 1.0 for all six LLFPs. This successful development and implementation of a transmutation system for LLFPs without isotope separation contribute to developing a self-consuming cycle of LLFPs using fast spectrum reactors to reduce radioactive waste.

Spectrum of heavy baryons in the quark model

Yoshida, Tetsuya*; Hiyama, Emiko*; Hosaka, Atsushi*; Oka, Makoto; Sadato, Katsunori*

Physical Review D, 92(11), p.114029_1 - 114029_19, 2015/12

https://doi.org/10.1103/PhysRevD.92.114029

Single- and double-heavy baryons are studied in the constituent quark model. The model Hamiltonian is chosen as a standard one with two exceptions: (1) the color-Coulomb term depends on quark masses and (2) an antisymmetric (spin-orbit) force is introduced. Model parameters are fixed by the strange baryon spectra, and baryons. The masses of the observed charmed and bottomed baryons are, then, fairly well reproduced. Our focus is on the low-lying negative-parity states, in which the heavy baryons show specific excitation modes reflecting the mass differences of heavy and light quarks. By changing quark masses from the SU(3) limit to the strange quark mass, and, further, to the charm and bottom quark masses, we demonstrate that the spectra change from the SU(3) symmetry patterns to the heavy-quark-symmetry ones.

Survey of radiation protection creiteria following the accident at the Fukushima Dai-ichi Nuclear Power Plant

Yamada, Katsunori; Fujii, Katsutoshi; Kanda, Hiroshi; Higashi, Daisuke; Kobayashi, Toshiaki; Nakagawa, Masahiro; Fukami, Tomoyo; Yoshida, Keisuke; Ueno, Yumi; Nakajima, Junya; et al.

JAEA-Review 2013-033, 51 Pages, 2013/12

JAEA-Review-2013-033.pdf:2.73MB

After the accident at Fukushima Dai-ichi Nuclear Power Plant, various numerical criteria relevant to radiation protection were defined. We surveyed these criteria through internet. As a result of survey, the following 13 items were identified: (1) criteria for taking stable iodine tablets, (2) criteria for the screening of surface contamination, (3) evacuation area, sheltering area, etc., (4) activity concentrations in food, drinking water, etc., (5) dose limit for radiation workers engaged in emergency work, (6) guideline levels of radioactive substances in bathing areas, (7) criteria for use of school buildings and schoolyards, (8) restriction on planting rice, (9) acceptable activity concentrations in feedstuff, (10) acceptable activity concentrations in compost, (11) criteria for export containers and ships, (12) criteria for contaminated waste, (13) standards for radiation workers engaged in decontamination work. In this report, the basis of and issues on these criteria are summarized.

Detection and temporal variation of Co in the digestive glands of the common octopus, , in the East China Sea

Morita, Takami*; Otosaka, Shigeyoshi; Fujimoto, Ken*; Nishiuchi, Ko*; Kimoto, Katsunori*; Yamada, Haruya*; Kasai, Hiromi*; Minakawa, Masayuki*; Yoshida, Katsuhiko*

Marine Pollution Bulletin, 60(8), p.1193 - 1199, 2010/08

https://doi.org/10.1016/j.marpolbul.2010.03.031

Significant concentrations of Co, Cs and Ag were detected in common octopus specimens collected in the East China Sea during two periods, 1986-1989 and 1996-2005. The radionuclides detected in the former period were thought to originate from the global fallout. On the other hand, the source of Co in the latter period has remained unclear because the Co concentration decreased continuously with shorter half-lives than the physical half-lives. This tendency suggests that the source of Co in 1996-2005 was identical and was temporary supplied to the East China Sea. Investigations of common octopus in the other area indicated that the origin of the pollutant source of Co in 1996-2005 occurred locally in the restricted area in the East China Sea rather than in the coastal area of Japan.

Remote maintenance technology for a large scale Hot Laboratory

Sakamoto, Naoki; Yoshikawa, Katsunori; Kushida, Naoya; Katsuyama, Kozo; Nagamine, Tsuyoshi

Proceedings of 46th Annual Meeting of "Hot Laboratories and Remote Handling" Working Group (HOTLAB 2009) (CD-ROM), 5 Pages, 2009/09

The large-scale post irradiation examination facility for fast breeder reactor fuel assemblies has been operated since 1978 in JAEAs Oarai Research and Development Center. The facility has several hot cells and irradiated fuel assemblies are dismantled in the examination cell which is 6 m in length, 19.5 m in width and 7 m in height. Remote maintenance technology for use in the hot laboratory was established using electromechanical manipulators, in-cell cranes and a repair hoist system installed in the examination cell. The test equipment which is used for post irradiation examinations can be repaired using the electromechanical manipulators and in-cell cranes by remote handling. In addition, the electromechanical manipulators and in-cell cranes are designed to permit self-repair using the repair hoist system in the cell by remote handling.

Eu isotope measurements on single SiC grains from the Murchison meteorite; A New probe of s-process conditions in parent Asymptotic Giant Branch stars

Terada, Kentaro*; Ito, Katsunori*; Hidaka, Hiroshi*; Yoshida, Takashi*; Iwamoto, Nobuyuki; Aoki, Wako*; Williams, I. S.*

New Astronomy Reviews, 50(7-8), p.582 - 586, 2006/10

https://doi.org/10.1016/j.newar.2006.06.006

Europium isotopic composition could be a good probe to investigate the neutron capture process in Asymptotic Giant Branch stars (AGB stars) and/or supernovae, because the Sm and Sm branchings are sensitive to the neutron densities and temperature. Here, we report Eu isotopic analyses of single SiC grains from primitive meteorites using the sensitive high resolution ion microprobe. The results are compared with Eu isotopic ratios predicted from the s-process model of AGB stars. The observed Eu isotopic composition of SiC grains place constraints on s-process conditions such as the temperature and neutron densities in AGB stars.

Objectives and design of the JT-60 superconducting tokamak

Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Chujo, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.

Nuclear Fusion, 43(7), p.606 - 613, 2003/07

https://doi.org/10.1088/0029-5515/43/7/314

no abstracts in English

R&D of a MW-class solid-target for spallation neutron source

Kawai, Masayoshi*; Furusaka, Michihiro*; Kikuchi, Kenji; Kurishita, Hiroaki*; Watanabe, Ryuzo*; Li, J.*; Sugimoto, Katsuhisa*; Yamamura, Tsutomu*; Hiraoka, Yutaka*; Abe, Katsunori*; et al.

Journal of Nuclear Materials, 318, p.35 - 55, 2003/05

R&D works for MW class solid target composed of tungsten to produce pulsed intense neutron source has been made in order to construct a future scattering facility. Three methods were investigated to prevent corrosion of tungsten from water; those are hipping, brazing and electric coating in molten salt bath. Hipping condition was optimized to be 1500 degree C in the previous work: here small punch test shows highest load for crack initiation of hipped materials at the boundary of W/Ta. The basic techniques for the other two methods were developed. Erosion test showed that uncovered W is susceptible of flowing water velocity. At high velocity w is easy to be eroded. For solid target design slab type and rod type targets were studied. As long as the optimized neutron performance is concerned, 1MW solid target is better than mercury target.

Uncertainty estimation of plume directions in atmospheric dispersion predictions; Application of Bayesian machine learning

Kadowaki, Masanao; Nagai, Haruyasu; Yoshida, Toshiya*; Terada, Hiroaki; Tsuzuki, Katsunori

no journal, , 

We have developed a method for quantitatively estimating the uncertainty in the direction of radioactive material plume dispersion in atmospheric dispersion predictions using an analytical model obtained by applying Bayesian machine learning to a database of long-term prediction calculation results. In this method, atmospheric dispersion calculations using analytical outputs of meteorological fields were defined as true values, and the uncertainty using forecast outputs was evaluated based on the difference in plume centroid between analysis and forecast outputs and Bayesian machine learning. To test this method, atmospheric dispersion calculations were performed using WSPEEDI-DB, with a hypothetical atmospheric release of Cs-137 from the Nuclear Science Research Institute in Ibaraki Prefecture. The calculation result showed that this method can effectively estimate the uncertainty in the direction of plume dispersion predicted by the atmospheric dispersion model.