Numerical simulation on self-leveling behavior of mixed particle beds using multi-fluid model coupled with DEM

Phan, L. H. S.*; Ohara, Yohei*; Kawata, Ryo*; Liu, X.*; Liu, W.*; Morita, Koji*; Guo, L.*; Kamiyama, Kenji; Tagami, Hirotaka

Proceedings of 12th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, Operation and Safety (NUTHOS-12) (USB Flash Drive), 12 Pages, 2018/10

Self-leveling behavior of core fuel debris beds is one of the key phenomena for the safety assessment of core disruptive accidents (CDAs) in sodium-cooled fast reactors (SFRs). The SIMMER code has been developed for CDA analysis of SFRs, and the code has been successfully applied to numerical simulations for key thermal-hydraulic phenomena involved in CDAs as well as reactor safety assessment. However, in SIMMER's fluid-dynamics model, it is always difficult to represent the strong interactions between solid particles as well as the discrete particle characteristics. To solve this problem, a new method has been developed by combining the multi-fluid model of the SIMMER code with the discrete element method (DEM) for the solid phase to reasonably simulate the particle behaviors as well as the fluid-particle interactions in multi-phase flows. In this study, in order to validate the multi-fluid model of the SIMMER code coupled with DEM, numerical simulations were performed on a series of self-leveling experiments using a gas injection method in cylindrical particle beds. The effects of friction coefficient on the simulation results were investigated by sensitivity analysis. Though more extensive validations are needed, the reasonable agreement between simulation results and corresponding experimental data preliminarily demonstrates the potential ability of the present method in simulating the self-leveling behaviors of debris bed. It is expected that the SIMMER code coupled with DEM is a prospective computational tool for analysis of safety issues related to solid particle debris bed in SFRs.

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.

Molecular and crystal structures of plutonyl(VI) nitrate complexes with N-alkylated 2-pyrrolidone derivatives; Cocrystallization potentiality of U and Pu

Kim, S.-Y.; Takao, Koichiro*; Haga, Yoshinori; Yamamoto, Etsuji; Kawata, Yoshihisa; Morita, Yasuji; Nishimura, Kenji*; Ikeda, Yasuhisa*

Crystal Growth & Design, 10(5), p.2033 - 2036, 2010/04

https://doi.org/10.1021/cg100015t

Plutonyl(VI) nitrate complexes with N-cyclohexyl-2-pyrrolidone (NCP) and N-neopentyl-2-pyrrolidone (NNpP) were prepared, and their molecular and crystal structures were determined by single crystal X-ray analysis. The obtained compounds have the similar composition, PuO(NO)(NRP) (NRP = NCP, NNpP), which are analogous to the corresponding U(VI) complexes. Both PuO(NO)(NRP) complexes show typical structural properties of actinyl(VI) nitrates, i.e., hexagonal-bipyramidal geometry consisting of two NRP molecules and two NO ions located in trans positions in the equatorial plane of PuO moiety. These findings provide one of criteria in selection of suitable NRP as a precipitation agent for the spent nuclear fuel reprocessing based on the precipitation method.

Effects of the surface condition of the substrates on the electrical characteristics of 4H-SiC MOSFETs

Oshima, Takeshi; Onoda, Shinobu; Kamada, Toru*; Hotta, Kazutoshi*; Kawata, Kenji*; Eryu, Osamu*

Materials Science Forum, 615-617, p.781 - 784, 2009/00

Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) were fabricated on p-type epitaxial 4H-SiC substrates with different surface conditions. These electrical characteristics were compared from a point of view of the surface condition. The MOSFETs on Chemical Mechanical Polished substrates showed the drain current of the order of 10 A at a gate voltage of zero. The drain current increased with increasing the surface roughness of substrates. With decreasing the surface roughness of substrates, the values of the threshold voltage decreased and the quality of gate oxide became better.

Progress in R&D efforts on the energy recovery linac in Japan

Sakanaka, Shogo*; Ago, Tomonori*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; Harada, Kentaro*; Hiramatsu, Shigenori*; Honda, Toru*; et al.

Proceedings of 11th European Particle Accelerator Conference (EPAC '08) (CD-ROM), p.205 - 207, 2008/06

Future synchrotron light sources based on the energy-recovery linacs (ERLs) are expected to be capable of producing super-brilliant and/or ultra-short pulses of synchrotron radiation. Our Japanese collaboration team is making efforts for realizing an ERL-based hard X-ray source. We report recent progress in our R&D efforts.

The Support Activities of JNC against the JCO Criticality Accident

Kanamori, Masashi; Kawata, Tomio; Hitoshi, Watanabe,; Tobita, Yoshiharu; Sugiyama, Toshihide; Miyabe, Kenjiro; Kobayashi, Hirohide

JNC TN8450 2003-009, 506 Pages, 2004/03

JNC-TN8450-2003-009.pdf:14.21MB

This paper describes all the activities that were executed by JNC related to JCO criticality accident on September 30,1999. During the JCO accident, the activities of radiation monitoring, environmental monitoring, criticality termination operation, computer simulation of criticality accident, whole body exposure measurements by WBC about 24-Na, back up of local government like consultation of residents near by were performed by JNC. After the accident Japanese government and Nuclear Safety Commission establishes the investigation committee of JCO accident. JNC has also back up this activity. For example, investigation of the causes, accident scenario, estimation of the doses of the workers and personnel for deserter, counter measure operation. This paper summarizes all the important activity executed by JNC in the meantime.

Development of advanced reprocessing system using high selective and controllable precipitants

Noda, Kyoko*; Takao, Koichiro*; Sugiyama, Yuichi*; Harada, Masayuki*; Nogami, Masanobu*; Maruyama, Koichi*; Takahashi, Hiroaki*; Kim, S.-Y.; Sato, Makoto; Mineo, Hideaki; et al.

no journal, , 

We have been developing an advanced reprocessing system for spent FBR fuels based on precipitation method using pyrrolidone derivatives. In previous investigation, N-cyclohexyl-2-pyrrolidone (NCP) is used as a precipitant, which is able to precipitate selectively UO ions in HNO solution, and a process consisting of two separation steps; selective U precipitation step and U-Pu co-precipitation step, was developed. In order to make the process more effective and more economical, we are now studying precipitation of U and Pu with other pyrrolidone derivatives. The outline of the study and main results obtained until now are shown in this presentation.

Development of advanced reprocessing system using high selective and controllable precipitants, 8; Co-precipitation behavior of U-Pu by novel precipitants with high hydrophobicity

Morita, Yasuji; Kim, S.-Y.; Kawata, Yoshihisa; Sato, Makoto; Ikeda, Yasuhisa*; Takao, Koichiro*; Noda, Kyoko*; Nishimura, Kenji*

no journal, , 

Precipitation behavior of Pu with pyrrolidone derivatives of N-(1,2-dimethyl)propyl-2-pyrrolidone (NDMProP) and N-neopenthyl-2-pyrrolidone (NNpP) in the solutions of U-Pu mixture has been examined in order to evaluate their applicability to the U-Pu co-precipitation process in the reprocessing based only on precipitation method. We have previously developed a process with N-cyclohexyl-2-pyrrolidone (NCP). It was found that U(VI) was precipitated in a high yield with any of the three precipitants and the precipitation yield of Pu(IV) was increased with the added amount of the precipitants. When NNpP was added with the ratio of [NNpP]/[U+Pu]=2.5, 99.5% of Pu was precipitate. Since NNpP showed the highest precipitation ability for Pu(IV) and the best physical property as precipitate, NNpP would be the most appropriate precipitant for the U-Pu co-precipitation process.

Development of advanced reprocessing system using high selective and controllable precipitants, 11; Structural analyses of Pu(VI) nitrate complexes with pyrrolidone derivatives

Kim, S.-Y.; Haga, Yoshinori; Yamamoto, Etsuji; Kawata, Yoshihisa; Morita, Yasuji; Ikeda, Yasuhisa*; Nishimura, Kenji*

no journal, , 

The crystal structure of plutonyl(VI) nitrate complexes, PuO(NO)(L) [L=N-cyclohexyl-2-pyrrolidone (NCP), N-Neopentyl-2-pyrrolidone (NNpP)] have been prepared by mixing PuO(NO) and L in an aqueous nitric acid solution and its crystal structure was determined using X-ray diffractometry and confirmed by IR spectroscopy. The plutonyl(VI) nitrate complexes with L normally have a composition of PuO(NO)(L), which shows common structural features, i.e., the plutonyl ion is surrounded by four oxygen atoms from two NO and two donating atoms of two L in its equatorial plane. X-ray diffraction study reveals that average distances between plutonium atom and plutonyl-, nitrate-, and carbonyl- oxygen atoms are 1.727-1.731 , 2.490-2.507 , 2.377-2.390 , respectively.

Development of advanced reprocessing system using high selective and controllable precipitants, 2; Precipitation behavior of Pu by novel pyrrolidone derivatives

Kim, S.-Y.; Kawata, Yoshihisa; Morita, Yasuji; Nogami, Masanobu*; Harada, Masayuki*; Ikeda, Yasuhisa*; Kikuchi, Toshiaki*; Nishimura, Kenji*

no journal, , 

A reprocessing system for spent FBR fuels based on the two precipitation processes has been proposed. In this system, first only U(VI) species are precipitated using pyrrolidone derivatives (NRP) with low hydrophobicity and donicity, and secondly residual U(VI) and Pu(IV, VI) are precipitated simultaneously using pyrrolidone derivative with high precipitation ability. It is important to control precipitation of Pu(IV), and recent advances on precipitation behavior of Pu(IV, VI) by using novel pyrrolidone derivatives will be introduced in this presentation. Precipitation tests using mixed solutions of U(VI) and Pu(IV) showed that N-n-butyl-2-pyrrolidone (NBP) is the most appropriate precipitant for the first precipitation step and N-neopenthyl-2-pyrrolidone (NNpP) is the most appropriate precipitant for the second step.