Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Yamamoto, Kento*; Akie, Hiroshi; Suyama, Kenya; Hosoyamada, Ryuji*
JAEA-Technology 2015-019, 110 Pages, 2015/10
JAEA-Technology-2015-019.pdf:3.67MB
In the direct disposal of used nuclear fuel (UNF), criticality safety evaluation is one of the important issues since UNF contains some amount of fissile material. The recent development of higher-enrichment fuel has enhanced the benefit of the application of Burnup Credit. In the present study, the effects of the several parameters on the reactivity of disposal canister model were evaluated for used PWR fuel. The parameters are relevant to the uncertainties of depletion calculation code, irradiation history, and axial and horizontal burnup distribution, which are known to be important effect in the criticality safety evaluation adopting burnup credit. The latest data or methodology was adopted in this evaluation, based on the various latest studies. The appropriate margin of neutron multiplication factor in the criticality safety evaluation for UNF can be determined by adopting the methodology described in the present study.
Yamamoto, Kento; Akie, Hiroshi; Suyama, Kenya
Proceedings of International Conference on Nuclear Criticality Safety (ICNC 2015) (DVD-ROM), p.228 - 237, 2015/09
Japan has recently started to study the technical issues for the direct disposal of the used nuclear fuel (UNF) to prepare various disposal options. The criticality safety is important for the direct disposal because of the presence of certain amount of the fissile nuclides in UNF. This paper gives the outline of the research to be addressed in this field and the relevant studies in Japan. Especially, it presents the first result of the criticality safety evaluation for a disposal canister model adopting burnup credit. The uncertainties of effective neutron multiplication factor (
) caused by the depletion calculation errors as well as the effect of the axial burnup profile and the horizontal burnup gradient on were also evaluated. It was found that the including these uncertainties and conservatism was below 0.95 for the representative used PWR fuel when the fuel assemblies and the disposal canister were assumed to keep intact.
Yamamoto, Kento; Okumura, Keisuke; Kojima, Kensuke; Okamoto, Tsutomu
Nuclear Back-end and Transmutation Technology for Waste Disposal, p.233 - 249, 2015/00
To improve the prediction accuracy of concentrations of activation products (APs) in the field of nuclear back-end, it is important to investigate the elements and the nuclear reactions leading to generation of APs. To clarify quantitatively the source elements and the nuclear reactions dominating generation of APs, sensitivity analyses of initial compositions and cross sections were conducted using ORIGEN2.2 code and ORLIBJ40, which is a set of the 1-group cross section libraries based on JENDL-4.0. Activations of cladding tubes, end-plugs and spacers of fuel assemblies and channel boxes in BWR, whose materials are zirconium alloy, stainless steel, and nickel-chromium-based alloy, were analyzed. The results clarified quantitatively the source elements and the nuclear reactions dominating generation of APs. It was remarkable that the dominant generation pathways were clarified even for the nuclides generated through complicated pathways. In conclusion, the results of sensitivity analyses could be utilized to select the objective of elements for measurements of impurities in the materials and of nuclear data for improvement of accuracy.
U in UO
and MOX fuelsYamamoto, Kento; Okumura, Keisuke
Journal of Nuclear Science and Technology, 51(4), p.568 - 573, 2014/04
Times Cited Count：3 Percentile：23.92(Nuclear Science & Technology)To clarify the generation pathway of U in burned fuels, which is an important nuclide for dose evaluation at various stages in fuel cycle, concentrations of U generated through various pathways were evaluated for UO and MOX fuels at 45 GWd/t using the ORIGEN2.2 code. It was found that the difference of U concentrations in UO and MOX fuel are mainly derived from the difference of the initial compositions of 
U, 
U and 
U and the contribution of plutonium and americium isotopes in MOX fuels is not so large compared with that of uranium isotopes. The results clarified that the capture cross sections of 
Th, 
Pa, U and U and (
,2) cross sections of Np and 
U have a large effect on generation of U. The additional investigation showed that not only time after irradiation but also time before irradiation has a strong effect on U concentration.
Yamamoto, Kento; Okumura, Keisuke; Kojima, Kensuke; Okamoto, Tsutomu
JAEA-Research 2013-038, 88 Pages, 2014/02
JAEA-Research-2013-038.pdf:3.15MB
Accurate information on main generation pathways of activation products is important to improve the accuracy of predicting the concentrations of activation products. Using ORIGEN2 and ORLIBJ40, which is a set of the cross section libraries based on JENDL-4.0, the initial compositions and the cross sections which influence on the concentrations of activation products were clarified by executing the sensitivity analyses on them. Activations of cladding tubes, end-plugs and spacers of fuel assemblies and channel boxes, which were composed of Zircaloy, SUS304, and Inconel-718, were analyzed. The main generation pathways of some significant activation products were summarized from the results of sensitivity analyses.
Okumura, Keisuke; Hagura, Hiroyuki; Kojima, Kensuke; Yamamoto, Kento; Tanaka, Kenichi*
no journal, ,
A method of the activation sensitivity analysis was developed for the optimization of the inventory evaluation of radionuclides in the waste generated in the decommissioning of LWR plants. By applying the method to a BWR plant, we clarified the impurity nuclides in the structural materials and their nuclear reactions contributing the generation of about fifty radioactive nuclides important for the processing and disposal of radioactive wastes.
Suyama, Kenya; Akie, Hiroshi; Kataoka, Masaharu*; Yamamoto, Kento*
no journal, ,
no abstracts in English
