Optimization of a slab geometry type cold neutron moderator for RIKEN accelerator-driven compact neutron source

Ma, B.*; Teshigawara, Makoto; Wakabayashi, Yasuo*; Yan, M.*; Hashiguchi, Takao*; Yamagata, Yutaka*; Wang, S.*; Ikeda, Yujiro*; Otake, Yoshie*

Nuclear Instruments and Methods in Physics Research A, 995, p.165079_1 - 165079_7, 2021/04

https://doi.org/10.1016/j.nima.2021.165079

We have optimized a cold neutron moderator to be operated at the RIKEN accelerator-driven compact neutron source. We selected a safe and easy to manage material, mesitylene, as the RANS cold moderator. An efficient moderator system was designed by studying and optimizing a coupled cold neutron moderator of mesitylene at 20 K with a polyethylene (PE) pre-moderator at room temperature in the slab geometry with Particle and Heavy Ion Transport code System (PHITS) simulations. The parameters of mesitylene and PE thickness, the reflector, and the shielding configuration were studied to increase cold neutron intensities. Consequently, an integrated cold neutron intensity of 1.1510n/cm/A at 2 m from the neutron-producing target was finally achieved, which was 12 times higher than that of the current PE moderator. The results showed attractive application prospect of mesitylene as cold neutron moderator material.

Local magnetic states of the weakly ferromagnetic iron-based superconductor SrVFeAsO studied by X-ray magnetic circular dichroism

Horio, Masafumi*; Takeda, Yukiharu; Namiki, Hiromasa*; Katagiri, Takao*; Wakabayashi, Yuki*; Sakamoto, Shoya*; Nonaka, Yosuke*; Shibata, Goro*; Ikeda, Keisuke*; Saito, Yuji; et al.

Journal of the Physical Society of Japan, 87(10), p.105001_1 - 105001_2, 2018/10

https://doi.org/10.7566/JPSJ.87.105001

Probabilistic risk assessment method development for high temperature gas-cooled reactors, 2; Development of accident sequence analysis methodology

Matsuda, Kosuke*; Muramatsu, Ken*; Muta, Hitoshi*; Sato, Hiroyuki; Nishida, Akemi; Ohashi, Hirofumi; Itoi, Tatsuya*; Takada, Tsuyoshi*; Hida, Takenori*; Tanabe, Masayuki*; et al.

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 7 Pages, 2017/04

This paper proposes a set of procedures for accident sequence analysis in seismic PRAs of HTGRs that can consider the unique accident progression characteristics of HTGRs. Main features of our proposed procedure are as follows: (1) Systematic analysis techniques including Master Logic Diagrams are used to ensure reasonable completeness in identification of initiating events and classification of accident sequences, (2) Information on factors that govern the accident progression and source terms are effectively reflected to the construction of event trees for delineation of accident sequences, and (3) Frequency quantification of seismically-initiated accident sequence frequencies that involve multiplepipe ruptures are made with the use of the Direct Quantification of Fault Trees by Monte Carlo (DQFM) method by a computer code SECOM-DQFM.

Precise determination of precipitation yield of uranyl nitrate with -alkylated 2-pyrrolidone derivatives

Takao, Koichiro*; Kawata, Yoshihisa*; Nogami, Masanobu*; Harada, Masayuki*; Morita, Yasuji; Nishimura, Kenji*; Ikeda, Yasuhisa*

Journal of Nuclear Science and Technology, 52(2), p.294 - 298, 2015/02

https://doi.org/10.1080/00223131.2014.937782

Yields of precipitated UO(NO)(NRP) (NRP = -alkylated 2-pyrrolidone) were precisely determined by considering reduction of the solution volume through the precipitation, which can be estimated from difference in acid concentrations of the liquid phases before and after the precipitation. The studied NRPs were --butyl (NBP) and --propyl (NProP) derivatives. In both systems, the precipitation yields precisely determined were always higher than those simply calculated from the ratio of uranium concentrations before and after the precipitation. However, the differences between them are in the range of 0.6% - 2.6%. If such a difference is practically negligible, the volume reduction through the precipitation does not have to be taken into account for simplicity of the analytical manipulation.

Identified charged hadron production in collisions at = 200 and 62.4 GeV

Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.

Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06

https://doi.org/10.1103/PhysRevC.83.064903

Transverse momentum distributions and yields for , and in collisions at = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different collisions. We also present the scaling properties such as and scaling and discuss the mechanism of the particle production in collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.

Zinc isotope fractionation in anion exchange in hydrochloric acid solution

Suzuki, Tatsuya*; Nomura, Masao*; Fujii, Yasuhiko*; Ikeda, Atsushi; Takaoka, Toru*; Oguma, Koichi*

Nihon Ion Kokan Gakkai-Shi, 21(3), p.328 - 333, 2010/09

Zinc isotope fractionation in an anion exchange resin has been investigated in hydrochloric acid solution by chromatographic technique. It was found that the heavier zinc isotopes were located disproportionately in the solution phase. The isotope fractionation coefficient was varied from the order of 10 to 10 depending on the hydrochloric acid concentration. The maximum isotope fractionation coefficient was obtained in 1 hydrochloric acid, while the distribution coefficient of zinc became maximum at around 2 hydrochloric acid. This difference has been further discussed based on the calculated speciation and structural information derived from X-ray absorption spectroscopy.

Neptunium carbonato complexes in aqueous solution; An Electrochemical, spectroscopic, and quantum chemical study

Ikeda, Atsushi; Tsushima, Satoru*; Takao, Koichiro*; Rossberg, A.*; Funke, H.*; Scheinost, A. C.*; Bernhard, G.*; Yaita, Tsuyoshi; Hennig, C.*

Inorganic Chemistry, 48(24), p.11779 - 11787, 2009/12

https://doi.org/10.1021/ic901838r

The electrochemical behavior and complex structure of Np carbonato complexes have been investigated in aqueous NaCO and NaCO/NaOH solutions at different oxidation states by using cyclic voltammetry, X-ray absorption spectroscopy, and density functional theory calculations. The end-member complexes of penta- and hexavalent Np in 1.5 M NaCO with pH = 11.7 have been determined as a transdioxo neptunyl tricarbonato complex, [NpO(CO)] ( = 5 for Np, and 4 for Np). In contrast, the electrochemical oxidation of Np in a highly basic carbonate solution of 2.0M NaCO/1.0M NaOH (pH 13) yielded a stable heptavalent Np complex of [Np O(OH)], indicating that the oxidation reaction from Np to Np in the carbonate solution involves a drastic structural rearrangement from the transdioxo configuration to a square-planar-tetraoxo configuration, as well as exchanging the coordinating anions from carbonate ions (CO) to hydroxide ions (OH).

Solubility of uranyl nitrate precipitates with -Alkyl-2-pyrrolidone derivatives (Alkyl = -propyl, -butyl, -butyl, and cyclohexyl)

Takao, Koichiro*; Noda, Kyoko*; Nogami, Masanobu*; Sugiyama, Yuichi*; Harada, Masayuki*; Morita, Yasuji; Nishimura, Kenji*; Ikeda, Yasuhisa*

Journal of Nuclear Science and Technology, 46(10), p.995 - 999, 2009/10

https://doi.org/10.3327/jnst.46.995

We have been developing an advanced reprocessing system for spent FBR fuels based on precipitation method using pyrrolidone derivatives. In the present study, the solubility of UO(NO)(NRP) (NRP = -alkyl-2-pyrrolidone, alkyl = -propyl, -butyl, -butyl and cyclohexyl) in aqueous solutions with HNO has been examined. As a result, the solubility of each species of UO(NO)(NRP) generally decreases with increasing concentrations of HNO and NRP ((HNO) and (NRP), respectively). The solubility of UO(NO)(NRP) also depends on the type of NRP; a higher hydrophobicity of NRP generally leads to a lower solubility of UO(NO)(NRP). The logarithms of effective solubility products () of UO(NO)(NRP) at different (HNO) values and 293 K were evaluated.

Molecular and crystal structures of uranyl nitrate complexes with -alkylated 2-pyrrolidone derivatives; Design and optimization of promising precipitant for uranyl ion

Takao, Koichiro*; Noda, Kyoko*; Morita, Yasuji; Nishimura, Kenji*; Ikeda, Yasuhisa*

Crystal Growth & Design, 8(7), p.2364 - 2376, 2008/07

https://doi.org/10.1021/cg7012254

Molecular and crystal structures of UO(NO)(NRP) (NRP = N-alkylated 2-pyrrolidone derivative) have been investigated by using single crystal X-ray analysis, IR and Raman spectroscopies. All UO(NO)(NRP) complexes have typical structural properties of UO(NO)(L) (L = unidentate ligand), i.e., hexagonal-bipyramidal geometry, two NRP and two NO located in trans positions in an equatorial plane of the uranyl ion. Observation of the crystals of the uranyl nitrate complexes with N-n-propyl-2-pyrrolidone and N-iso-propyl-2-pyrrolidone indicate the presence of significant voids in the crystal lattices of these compounds. From this result, an approach for construction of efficient packing of UO(NO)(NRP) was proposed. Consequently, it was found that N-iso-butyl-2-pyrrolidone completely satisfies with the requirement for the efficient packing by filling the voids with the alkyl chain.

Development of advanced reprocessing system based on use of pyrrolidone derivatives as novel precipitants with high selectivity and control ability, 1; Concept of advanced reprocessing system and precipitation behavior of U(VI)

Ikeda, Yasuhisa*; Takao, Koichiro*; Harada, Masayuki*; Morita, Yasuji; Nogami, Masanobu*; Nishimura, Kenji*

Proceedings of International Conference on Advanced Nuclear Fuel Cycles and Systems (Global 2007) (CD-ROM), p.1503 - 1507, 2007/09

We have developed a reprocessing process for spent FBR fuels based on the precipitation method using pyrrolidone derivatives. In previous investigation, N-cyclohexyl-2-pyrrolidone (NCP) is used as a precipitant and a process consisting of selective U precipitation step and U-Pu co-precipitation step was developed. In the present study, in order to examine the applicability of precipitants with lower hydrophobicity than NCP to the selective U precipitation step, we have carried out precipitation experiments of U(VI) by N-butyl-2-pyrrolidone (NBP) and N-propyl-2-pyrrolidone (NProP) and measured decontamination factors of some fission products.