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Np and 
Am by accelerator-driven system at Kyoto University Critical AssemblyPyeon, C. H.*; Yamanaka, Masao*; Oizumi, Akito; Fukushima, Masahiro; Chiba, Go*; Watanabe, Kenichi*; Endo, Tomohiro*; Van Rooijen, W. G.*; Hashimoto, Kengo*; Sakon, Atsushi*; et al.
Journal of Nuclear Science and Technology, 56(8), p.684 - 689, 2019/08
Times Cited Count：12 Percentile：80.27(Nuclear Science & Technology)This study demonstrates, for the first time, the principle of nuclear transmutation of minor actinide (MA) by the accelerator-driven system (ADS) through the injection of high-energy neutrons into the subcritical core at the Kyoto University Critical Assembly. The main objective of the experiments is to confirm fission reactions of neptunium-237 (Np) and americium-241 (Am), and capture reactions of Np. Subcritical irradiation of Np and Am foils is conducted in a hard spectrum core with the use of the back-to-back fission chamber that obtains simultaneously two signals from specially installed test (Np or Am) and reference (uranium-235) foils. The first nuclear transmutation of Np and Am by ADS soundly implemented by combining the subcritical core and the 100 MeV proton accelerator, and the use of a lead-bismuth target, is conclusively demonstrated through the experimental results of fission and capture reaction events.
Nishihara, Kenji; Iwamura, Takamichi*; Akie, Hiroshi; Nakano, Yoshihiro; Van Rooijen, W.*; Shimazu, Yoichiro*
Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.388 - 395, 2015/09
The present study focuses on transmutation of Pu and minor actinide in Japanese case without utilizing Pu as resource. Pu can be transmuted by two groups of technology: conventional ones without reprocessing of spent fuel from transmuter and advanced ones with reprocessing. Necessary number of transmuters, inventory reduction of actinide and impact on repository are revealed by nuclear material balance analysis. As a whole advanced technology performs better in transmutation efficiency, although required number of transmuters is larger.
Yamano, Naoki*; Iwamoto, Osamu; Nakamura, Shoji; Kunieda, Satoshi; Van Rooijen, W.*; Koura, Hiroyuki
JAEA-Conf 2014-002, 209 Pages, 2015/02
JAEA-Conf-2014-002.pdf:64.24MB
The 2013 Symposium on Nuclear Data was held at Research Institute of Nuclear Engineering, University of Fukui, on 14th and 15th of November 2013. The Nuclear Data Division of the Atomic Energy Society of Japan and Research Institute of Nuclear Engineering, University of Fukui organize this symposium in cooperation with Nuclear Science and Engineering Center of Japan Atomic Energy Agency and the Chubu Branch of Atomic Energy Society of Japan. In the oral sessions, papers were presented on topics of progress in neutron cross-section measurement and analysis, application of nuclear data, recent topics on nuclear data measurement and theory, and progress in studies of high-energy nuclear reactions. In the poster session, papers were presented concerning experiments, evaluations, benchmark tests and applications. This report consists of total 35 papers including 14 oral presentations and 21 poster presentations.
Truchet, G.*; Van Rooijen, W. F. G.*; Shimazu, Yoichiro*; Yamaguchi, Katsuhisa
Annals of Nuclear Energy, 51, p.94 - 106, 2013/01
Times Cited Count：6 Percentile：44.02(Nuclear Science & Technology)The Modified Neutron Source Method (MNSM) is applied to the prototype FBR Monju. Among Monju's particularities that have a big influence on the MNSM factors are: the presence of two californium sources near the core and the position of the detector, which is located far from the core outside of the reactor vessel. In order to evaluate the detector count rate, a propagation calculation has been conducted from the reactor vessel to the external detector. For two subcritical states, an estimation of the reactivity has been made and compared to experimental data obtained in the restart experiments at Monju (2010). Results indicate a good agreement between the MNSM reactivity and the reactivity measured with other methods.
Van Rooijen, W. F. G.*; Chiba, Go
Annals of Nuclear Energy, 38(1), p.133 - 144, 2011/01
Times Cited Count：15 Percentile：73.97(Nuclear Science & Technology)The present work discusses the calculation of the diffusion coefficient of a lattice of hexagonal cells, with both "sodium present" and "sodium absent" conditions. Calculations are performed in the framework of lattice theory. Unlike the classical approaches, our heterogeneous leakage model allows the calculation of diffusion coefficients under all conditions, even if planar voids are present in the lattice. Equations resulting from this model are solved using the method of characteristics (MOC). Independent confirmation of the MOC result comes from Monte Carlo calculations, in which the diffusion coefficient is obtained without any of the assumptions of lattice theory. It is shown by comparison to the Monte Carlo results that the MOC solution yields correct values of the diffusion coefficient under all conditions, even in cases where the classic calculation of the diffusion coefficient fails.
Van Rooijen, W. F. G.*; Hazama, Taira; Takeda, Toshikazu*
Proceedings of Joint International Conference of 7th Supercomputing in Nuclear Application and 3rd Monte Carlo (SNA + MC 2010) (USB Flash Drive), 14 Pages, 2010/10
For the reactor physics analysis of fast critical assemblies as well as LMFBRs, the diffusion coefficient is one of the required pieces of data. In the present analysis, the diffusion coefficient is determined using the Benoist-formalism, which is based on directional collision probabilities. For LMFBR analysis including void regions, the Benoist-formalism breaks down if two-dimensional (slab or slab-like) void regions are present. Furthermore, the Benoist-style assumption of zero buckling is questionable in fast reactors. Research is being done to identify improved cell calculations, in order to calculate the diffusion coefficient in one- and two-dimensional unit cells containing real void regions.
Chiba, Go; Van Rooijen, W. F. G.*
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Anisotropic diffusion coefficients for voided hexagonal lattices, which cannot be obtained using the classical benoist formalism, are successfully calculated with the method of characteristics. The proposed method is free from the divergence problem, and results in more rigorous diffusion coefficients based on the leakage theory.
Chiba, Go; Van Rooijen, W. F. G.*
no journal, ,
A property of a lattice composed of asymmetric unit cells is investigated. It is shown that usual deterministic calculation procedure based on the unit cell homogenization works well even if the unit cell is asymmetric by considering a direction dependence of homogenized total cross sections.
Yamaguchi, Katsuhisa; Truchet, G.*; Van Rooijen, W. F. G.*; Shimazu, Yoichiro*
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Konomura, Mamoru; Tamagno, P.*; Takeda, Toshikazu*; Van Rooijen, W. F. G.*
no journal, ,
Konomura, Mamoru; Tamagno, P.*; Van Rooijen, W. F. G.*; Takeda, Toshikazu*
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