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Sakakibara, Hiroshi; Aoki, Nobuhiro; Muto, Masahiro; Otabe, Jun; Takahashi, Kenji*; Fujita, Naoyuki*; Hiyama, Kazuhiko*; Suzuki, Hirokazu*; Kamogawa, Toshiyuki*; Yokosuka, Toru*; et al.
JAEA-Technology 2020-020, 73 Pages, 2021/03
JAEA-Technology-2020-020.pdf:8.26MB
The decommissioning is currently in progress at the prototype fast breeder reactor Monju. Fuel assemblies will be taken out of its core for the first step of the great task. Fuel assemblies stand on their own spike plugged into a socket on the core support plate and support with adjacent assemblies through their housing pads each other, resulting in steady core structure. For this reason, some substitutive assemblies are necessary for the purpose of discharging the fuel assemblies of the core. Monju side commissioned, therefore, Plutonium Fuel Development Center to manufacture the substitutive assemblies and the Center accepted it. This report gives descriptions of design, manufacture, and shipment in regard to the substitutive assemblies.
Ikusawa, Yoshihisa; Morimoto, Kyoichi; Kato, Masato; Saito, Kosuke; Uno, Masayoshi*
Nuclear Technology, 205(3), p.474 - 485, 2019/03
Times Cited Count：2 Percentile：21.58(Nuclear Science & Technology)This study evaluated the effects of plutonium content and self-irradiation on the thermal conductivity of mixed-oxide (MOX) fuel. Samples of UO
fuel and various MOX fuels were tested. The MOX fuels had a range of plutonium contents, and some samples were stored for 20 years. The thermal conductivity of these samples was determined from thermal diffusivity measurements taken via laser flash analysis. Although the thermal conductivity decreased with increasing plutonium content, this effect was slight. The effect of self-irradiation was investigated using the stored samples. The reduction in thermal conductivity caused by self-irradiation depended on the plutonium content, its isotopic composition, and storage time. The reduction in thermal conductivity over 20 years' storage can be predicted from the change of lattice parameter. In addition, the decrease in thermal conductivity caused by self-irradiation was recovered with heat treatment, and recovered almost completely at temperatures over 1200 K. From these evaluation results, we formulated an equation for thermal conductivity that is based on the classical phonon-transport model. This equation can predict the thermal conductivity of MOX fuel thermal conductivity by accounting for the influences of plutonium content and self-irradiation.
Saito, Kosuke; Nogami, Yoshitaka; Kodato, Kazuo; Matsuyama, Kazutomi; Endo, Hideo
JAEA-Research 2012-027, 118 Pages, 2012/09
JAEA-Research-2012-027.pdf:21.12MB
This report is compilation of 4 years tests and experiments of simulated alpha-ray irradiation on diverse materials for glove box application at Plutonium Fuel Development Center, Tokai, JAEA. Specimens prepared from the materials are irradiated with 
He
ion beam whose kinetic energy was 5 MeV and sent to exterior observation, optical microscopy and tensile tests. Experiments revealed ion-irradiation generally makes tens of micrometers of deteriorated layer which is hardened and discolored on the surface of the specimens. According to dose, tensile properties such as tensile strength and elongation at break decrease generally. Tensile strength decrease is expected to ascribe to stress concentration on cracks of irradiation-damaged surface and rupture. Lead-contained glove, which is ordinarily used on highly 
-radiative environments, saturates the decrease of its tensile strength around fluence of 1.4e+14 cm
. In addition, deterioration was accelerated for tension-loaded material and the saturation is around 4.6e+13 cm for 100%-extended specimens. The candidates of alternative new materials are two kinds of developed chlorosulfonated polyethylene (CSM) and conductive rubber, which were experimented and tested in like manner. From the results and inherent properties of these materials, one kind of CSM and conductive rubber are relatively promising. Gloves used at low-dose environments and vinyl chloride applied for glove ports were also experimented and tested, and quantitative data were which are useful for life-elongation measure obtained. The irradiation tests on this report are unprecedented ones with low-energy ion, and the obtained quantitative data of material properties and deterioration are scientifically rare and important.
Saito, Kosuke; Maeda, Seiichiro; Higuchi, Masashi*; Takano, Mitsuhiro*; Nakazawa, Hiroaki
JAEA-Technology 2006-035, 76 Pages, 2006/06
JAEA-Technology-2006-035.pdf:5.25MB
Because of the revision on the standardized strength of the ODS steel, the previous design study of MONJU demonstrative core has been obliged to be reconsidered. For economical advantages, only a 127 pins-bundle core was selected to be redesigned. For the sake of cladding endurance, the ratio of cladding thickness to outer diameter was reset incrementally followed by the determination of the basic specification of a pin. Notwithstanding some deterioration thanks to the reduction of a fuel volume fraction, the prospect in neutronics was obtained. Coolant flow distribution design which was based on power distribution was successfully carried out without overheating cladding. Average burn-up of 150 GWd/t and 380 days-long operational period per cycle are to be attained, and the designed core can thermally afford to receive test fuels. The study has necessity to be advanced extensively for the purpose of materialization according to the circumstances of MONJU in future.
Kitano, Akihiro; Mori, Tetsuya; Nagata, Akito*; Saito, Kosuke; Misawa, Tsuyoshi*; Tamagawa, Yoichi*
no journal, ,
no abstracts in English
-ray irradiation to polyethylene, polystyrene and cellulose resinSaito, Kosuke
no journal, ,
At 23rd July 2010, a fire accident broke out in Plutonium Fuel Development Center (Pu Center), Tokai, JAEA. The fire was occurred from the cylindrical container of stainless steel in a glove box which loaded uranium and plutonium compounds. In order to clear up the cause of the fire, Pu Center studied it from all angles. For one of the possible causes, some inflammable gas and/or hydrogen gas were deduced to be generated from irradiated plastic cases and/or cellulose resin which are organic substances in the stainless container. The plastic cases, which were used to reposit nuclear materials, are made of both polyethylene (PE) and polystyrene (PS). The both polymer was known to be decomposed by -ray irradiation and generate hydrogen gas, whose quantitative evaluation as absorbed dose was reported. As for PE, other gases such as carbon oxides, methane and ethane are produced. Cellulose resin was used for binder of uranium nitride powder, but gas generation from cellulose resin by -ray irradiation has not been reported. Then, in order to demonstrate and investigate hydrogen and inflammable-gas generation from polymers and cellulose resins, -ray irradiation to the materials and analyses of the generated gaseous substances were performed.
Tazawa, Yuto; Hosogane, Tatsuya; Ishikawa, Fumitaka; Kayano, Masashi; Matsuyama, Kazutomi; Saito, Kosuke; Oishi, Shinichi*; Nakajima, Hiroshi*
no journal, ,
no abstracts in English
Sakakibara, Hiroshi; Aoki, Nobuhiro; Muto, Masahiro; Otabe, Jun; Takahashi, Kenji*; Fujita, Naoyuki*; Hiyama, Kazuhiko*; Suzuki, Hirokazu*; Kamogawa, Toshiyuki*; Yokosuka, Toru*; et al.
no journal, ,
no abstracts in English
