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Ibaraki, Japan

Usuda S.,Tohoku University | Usuda S.,NAIS Co. Inc. | Yamanishi K.,Tohoku University | Mimura H.,Tohoku University | And 4 more authors.
Journal of Radioanalytical and Nuclear Chemistry | Year: 2014

Extraction chromatographic separation of trivalent minor actinides (MA: Am and Cm) was investigated by using solid adsorbents impregnating the lipophilic diamide-type ligands, TODGA (N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide) and DOODA(C8) (N,N,N′,N′-tetraoctyl-3,6-dioxaoctane-1,8-diamide). In nitric acid eluents, hydrophilic diamide-type ligands, DOODA(C2) (N,N,N′,N′-tetraethyl-3,6-dioxaoctanediamide) and TEDGA (N,N,N',N'-tetraethyl-diglycolamide) were included for the respective adsorbents as masking agents in order to produce a synergistic effect in mutual separation of Am and Cm. The adsorption tendency of Am and Cm for the adsorbents was opposite each other, that was similar to the case of lanthanides. © 2014 Akadémiai Kiadó, Budapest, Hungary.

Naito Y.,NAIS Co. Inc. | Yamamoto T.,Kyoto University | Misawa T.,Kyoto University | Yamane Y.,Japan Atomic Energy Agency
Journal of Nuclear Science and Technology | Year: 2013

Since the early 1960s, many studies on criticality safety evaluation have been conducted in Japan. Computer code systems were developed initially by employing finite difference methods, and more recently by using Monte Carlo methods. Criticality experiments have also been carried out in many laboratories in Japan as well as overseas. By effectively using these study results, the Japanese Criticality Safety Handbook was published in 1988, almost the intermediate point of the last 50 years. An increased interest has been shown in criticality safety studies, and a Working Party on Nuclear Criticality Safety (WPNCS) was set up by the Nuclear Science Committee of Organisation Economic Co-operation and Development in 1997. WPNCS has several task forces in charge of each of the International Criticality Safety Benchmark Evaluation Program (ICSBEP), Subcritical Measurement, Experimental Needs, Burn-up Credit Studies and MinimumCritical Values. Criticality safety studies in Japan have been carried out in cooperation with WPNCS. This paper describes criticalitysafety study activities in Japan along with the contents of the Japanese Criticality Safety Handbook and the tasks of WPNCS. © 2013 Copyright Taylor and Francis Group, LLC.

Yamamoto T.,Japan Nuclear Energy Safety Organization | Ando Y.,Japan Nuclear Energy Safety Organization | Hayashi Y.,Toshiba Corporation | Azekura K.,NAIS Co. Inc.
Journal of Nuclear Science and Technology | Year: 2012

Critical experiments were performed in the REBUS program on a core loaded with a test bundle including 16 irradiated BWR-type MOX rods of average burnup of 61 GWd/t. The experimental data were analyzed using diffusion, transport, and continuous-energy Monte Carlo calculation codes coupled with nuclear data libraries based on JENDL-3.2 or JENDL-3.3. Biases in effective multiplication factors of the critical cores were -1.0%Δk for the diffusion calculations (JENDL-3.2), -0.3%Δk for the transport calculations (JENDL-3.3), and 0.2%Δk for the Monte Carlo calculations (JENDL-3.2). The measured core fission rate and co-activation rate distributions were generally well reproduced using the three types of calculations. The burnup reactivity determined using the measured water level reactivity coefficients was -2.41±0.08%Δk/ kk', which also agreed with the results of the three type of calculations within the measurement and calculation errors. The most probable isotopic inventories in the irradiated MOX rods was tentatively obtained by using the ratios of the calculation to chemical assay data on a pellet sample, and the burnup reactivity was reanalyzed to split the calculation error into those due to the inventory and reactivity calculations. This approach showed that the inventory calculation error compensated the reactivity calculation error. © 2012 Atomic Energy Society of Japan. All rights reserved.

Yamamoto T.,Japan Nuclear Energy Safety Organization | Sakai T.,Japan Nuclear Energy Safety Organization | Ando Y.,Japan Nuclear Energy Safety Organization | Liem P.H.,NAIS Co. Inc. | Kikuchi S.,Toshiba Corporation
Journal of Nuclear Science and Technology | Year: 2012

A part of the experimental program FUBILA was dedicated to the study of core physics characteristics of full MOX BWR cores by testing five experimental cores: a core inserted with a B 4C control blade, a core loaded with UO 2 fuel rods, the core loaded with Gd 2O 3-UO 2 fuel rods, a core loaded with 10×10 MOX assemblies and a core loaded with time-elapsed MOX fuel. The present article describes analysis results of the experimental data with deterministic analysis codes and a continuous energyMonte Carlo code coupled with major nuclear data libraries. The calculated critical keff's with the Monte Carlo calculations range from 0.999 to 1.007. Those of the transport calculations with sixteen energy groups are close to those of the Monte Carlo calculations while those of diffusion calculations with the same sixteen energy groups are systematically smaller by -0.3 to -0.5% δk than those of the Monte Carlo calculations. The RMSs of differences between the calculated and measured core radial fission rates are 2 to 3%, 1 to 2%, and 1 to 2% for the diffusion, transport and Monte Carlo calculations, respectively. For the analysis of the Gd 2O 3-UO 2 fuel rod loaded core, the C/Es of the radial fission rates were improved by adopting a detailed lattice calculation model and a newly measured thermal and resonance cross-sections of Gadolinium. © 2012 Atomic Energy Society of Japan. All rights reserved.

Sakurai T.,Japan Atomic Energy Agency | Mori T.,Japan Atomic Energy Agency | Suzaki T.,Japan Atomic Energy Agency | Okajima S.,Japan Atomic Energy Agency | And 3 more authors.
Journal of Nuclear Science and Technology | Year: 2011

The reactivity worths of 22.82 grams of 241Am oxide sample were measured and theoretically analyzed in water-moderated UO2 fuel lattices in seven cores of the Tank-Type Critical Assembly (TCA) at the Japan Atomic Energy Agency for an integral test of 241Am nuclear data. These cores provided a systematic variation in the neutron spectrum between the thermal and resonance energy regions. The sample reactivity worth was measured with an uncertainty of 2.1% or less. The theoretical analysis was performed using the JENDL-3.3 nuclear data by a Monte Carlo calculation method. Ratios of calculation to experiment (C/Es) of the reactivity worth were between 0.91 and 0.97, and showed no apparent dependence on the neutron spectrum. In addition, sensitivity analysis based on the deterministic calculation method was carried out to obtain the impact of changing the 241Am capture cross section on the sample reactivity worth. The result of this analysis showed that the C/E could be significantly improved by almost uniformly increasing the 241Am capture cross section of JENDL-3.3 by 25-30%. © 2011 Atomic Energy Society of Japan, All Rights Reserved.

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