Li, C.-Y.; Watanabe, Akira*; Uchibori, Akihiro; Okano, Yasushi
Dai-26-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2022/07
Identifying accident scenarios that could lead to severe accidents and evaluating their frequency of occurrence are essential issues. This study aims to establish the methodology of the dynamic Probabilistic Risk Assessment (PRA) for sodium-cooled fast reactors that can consider the time dependency and the interdependence of each event. Specifically, the Continuous Markov chain Monte Carlo (CMMC) method is newly applied to the SPECTRA code, which analyzes the severe accident conditions of nuclear reactors, to develop an evaluation methodology for typical external hazards. Currently, a fault-tree model of air coolers of decay heat removal system is implemented as the CMMC method, and a series of preliminary analysis of the plant's transient characteristics under the scenario of volcanic ashfall has been conducted.
Li, C.-Y.; Uchibori, Akihiro; Takata, Takashi; Pellegrini, M.*; Erkan, N.*; Okamoto, Koji*
Dai-25-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 4 Pages, 2021/07
The capability of stable cooling and avoiding re-criticality on the debris bed are the main issues for achieving IVR (In-Vessel Retention). In the actual situation, the debris bed is composed of mixed-density debris particles. Hence, when these mixed-density debris particles were launched to re-distribute, the debris bed would possibly form a density-stratified distribution. For the proper evaluation of this scenario, the multi-physics model of CFD-DEM-Monte-Carlo based neutronics is established to investigate the coolability and re-criticality on the heterogeneous density-stratified debris bed with considering the particle relocation. The CFD-DEM model has been verified by utilizing water injection experiments on the mixed-density particle bed in the first portion of this research. In the second portion, the coupled system of the CFD-DEM-Monte-Carlo based neutronics model is applied to reactor cases. Afterward, the debris particles' movement, debris particles' and coolant's temperature, and the k-eff eigenvalue are successfully tracked. Ultimately, the relocation and stratification effects on debris bed's coolability and re-criticality had been quantitatively confirmed.
Kamide, Hideki; Shibata, Taiju
NREL/TP-6A50-77088 (Internet), p.35 - 38, 2020/09
Omer, M.; Shizuma, Toshiyuki*; Hajima, Ryoichi*
Nuclear Instruments and Methods in Physics Research A, 951, p.162998_1 - 162998_6, 2020/01
Yamamoto, Masahiko; Do, V. K.; Taguchi, Shigeo; Kuno, Takehiko; Takamura, Yuzuru*
Spectrochimica Acta, Part B, 155, p.134 - 140, 2019/05
The emission spectra of technetium (Tc) by liquid electrode plasma optical emission spectrometry have been investigated in this study. From the spectra, 52 emission peaks of Tc were observed in the 250-500 nm wavelength range. All peaks were assigned to the neutral state or singly ionized state. The relative intensities of these peaks were similar to those excited by an electric spark. The strongest intensity peaks were found at 254.3 nm, 261.0 nm, and 264.7 nm. Spectral interferences of coexisting elements in highly active liquid waste of reprocessing stream on those three strongest peaks were investigated using simulated sample. No spectral interferences were observed around the 264.7 nm Tc peak. Therefore, analytical performance using 264.7 nm peak was evaluated. The detection limit, estimated on standard and blank samples in 0.4 M nitric acid, was 1.9 mg/L. The relative standard deviation of Tc standard sample (12.0 mg/L) was 3.8% (N = 5, 1).
erovnik, G.*; Schillebeeckx, P.*; Becker, B.*; Fiorito, L.*; Harada, Hideo; Kopecky, S.*; Radulovic, V.*; Sano, Tadafumi*
Nuclear Instruments and Methods in Physics Research A, 877, p.300 - 313, 2018/01
Methodologies to derive cross section data from spectrum integrated reaction rates were studied. The Westcott convention and some of its approximations were considered. The accuracy of the results strongly depends on the assumptions that are made about the neutron energy distribution, which is mostly parameterised as a sum of a thermal and an epi-thermal component. Resonance integrals derived from such data can be strongly biased. When the energy dependence of the cross section is known and information about the neutron energy distribution is available, a method to correct for a bias on the cross section at thermal energy is proposed. Reactor activation measurements to determine the thermal Am(n, ) cross section reported in the literature were reviewed, where the results were corrected to account for possible biases. These data combined with results of time-of-flight measurements give a capture cross section 720 (14) b for Am(n, ) at thermal energy.
Kasugai, Yoshimi; Harada, Masahide; Kai, Tetsuya; Oi, Motoki; Meigo, Shinichiro; Maekawa, Fujio
JAEA-Data/Code 2015-033, 28 Pages, 2016/03
The high-energy neutron fluxes and spectra around the mercury spallation neutron source at MLF of J-PARC were measured by the multi-foil activation method. The threshold energies of neutron reactions utilized in this experiment covered from 0.1 to 50 MeV. The foil irradiation was carried out on the first beam-run of MLF from May 30th to 31th, 2008. After the irradiation, the induced radioactivity of each foil was measured using an HPGe detector, and the neutron-induced reaction-rate distribution around the mercury target was determined. Using these data, the high-energy neutron fluxes and spectra were deduced with unfolding method in which the neutron spectra calculated with PHITS code were used as the initial-guess spectra. By comparison between the initial and the unfolded spectra, it was shown that most of the calculation results, which had been the basis of the neutronics design of the MLF target assembly, were consistent with the experimental data within 30%.
Iwamoto, Yosuke; Taniguchi, Shingo*; Nakao, Noriaki*; Itoga, Toshio*; Nakamura, Takashi*; Nakane, Yoshihiro; Nakashima, Hiroshi; Satoh, Daiki; Yashima, Hiroshi*; Yamakawa, Hiroshi*; et al.
Nuclear Instruments and Methods in Physics Research A, 562(2), p.789 - 792, 2006/06
Neutron energy spectra produced from thick targets play an important role in validation of calculation codes that are employed in the design of spallation neutron sources and the shielding design of accelerator facilities. However, appropriate experimental data were scarce in the forward direction for the incident energy higher than 100 MeV. In this study, neutron spectra at 0 degree from thick targets bombarded with 350 MeV protons were measured by the time-of-flight technique using an NE213. The targets used were graphite, Al, Fe and Pb and their thicknesses were chosen to be a little thicker than the stopping lengths. The experiment was carried out at the TOF course of the RCNP (Research Center of Nuclear Physics) ring cyclotron, Osaka University. The flight path length between center of the target and of an NE213 were 11.4 m for the measurement of low energy neutrons and 95 m for high energy neutrons. The experimental data are compared with the calculated results by using the Monte Carlo transport codes, such as MCNPX and PHITS codes.
Kubo, Hirotaka; Sataka, Masao; Shirai, Toshizo
Journal of Plasma and Fusion Research SERIES, Vol.7, p.352 - 355, 2006/00
no abstracts in English
Kato, Takako*; Murakami, Izumi*; Goto, Motoshi*; Morita, Shigeru*; Ida, Katsumi*; Peterson, B. J.*; Funaba, Hisamichi*; Nakano, Tomohide
Journal of Plasma and Fusion Research SERIES, Vol.7, p.1 - 4, 2006/00
We analyzed impurity VUV spectral emission quantitatively. Electron temperature is derived from the intensity ratio of CIII line intensities. Radiation loss sources are identified using spectroscopy and bolometer in the case of radiation collapse caused by neon gas puffing. Time dependent radiation loss of impurity ions are derived from line intensities of impurities.
Chen, J.; Asano, Masaharu; Tsubokawa, Norio*; Maekawa, Yasunari; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Polymer Science, Part B; Polymer Physics, 43(20), p.2843 - 2851, 2005/10
Impedance spectra analysis of a thermo-responsive poly(acryloyl--proline methyl ester) (poly(A-ProOMe)) hydrogel membranes in an aqueous solution of LiCl was carried out using a simple equivalent model. The hydrogel membrane was synthesized by -radiation-induced polymerization and crosslinking of A-ProOMe monomer aqueous solution in a glass-cast. By means of the impedance spectra analysis, a novel method for the calculation of the ionic conductivity of the hydrogel membranes in LiCl solution was proposed. The calculated ionic conductivity was in agreement well with the determined value. In addition, effects of temperature and LiCl concentration on the impedance spectra and ionic conductivity of the gel membrane were analysized. Results indicated that the impedance spectra analysis is a very useful tool for evaluating the electric properties of gel membranes in an electrolyte solution. The poly(A-ProOMe) gel membrane in 1.0 M LiCl solution showed a high ionic conductivity of about 0.2 S/cm at 14C. The temperature-dependence of the ionic conductivity was a complex nonlinear form due to the volume phase transition of the thermo-responsive poly(A-ProOMe) gel membrane, and the volume phase transition temperature appeared to be decreased with the increase in the LiCl concentration.
Yoshizawa, Michio; Tanimura, Yoshihiko; Saegusa, Jun; Nemoto, Hisashi*; Yoshida, Makoto
Radiation Protection Dosimetry, 110(1-4), p.81 - 84, 2004/09
The facility of Radiation Standards (FRS) of JAERI has equipped with the concrete-moderated neutron calibration fields as simulated workplace neutron fields. The fields use an Am-Be (37GBq) neutron source placed in the narrow space surrounded by concrete wall and bricks to produce scattered neutrons. The neutron spectra of the fields were measured with Bonner multi-sphere spectrometer system (BMS), spherical recoil-proton proportional counters (RPCs), and a liquid scintillation counter (NE-213). The results were compared with each other, and the neutron spectra and the ambient dose equivalent rate, (10), were agreed well within the uncertainty. The angular distributions of neutron fluence were calculated by the MCNP-4B2 Monte Carlo code to obtain the reference personal dose equivalent rate, (10). The calculated results show that the scattered neutrons have a wide variety of incident angles. The reference (10) values considered the angular distribution were found to be 10-18% smaller than those without consideration.
Bruskin, L. G.*; Oyama, Naoyuki; Mase, Atsushi*; Shinohara, Koji; Miura, Yukitoshi
Plasma Physics and Controlled Fusion, 46(8), p.1313 - 1330, 2004/08
no abstracts in English
Shimizu, Shigeru; Zhang, Q.; Kajimoto, Yoichi; Kawasaki, Tomokatsu; Fujii, Katsutoshi
JAERI-Tech 2003-095, 52 Pages, 2004/01
The International Standards ISO4037-1 of the International Organization for Standardization widely applied in the world to construct X-ray reference fields for performance tests of radiation measuring instruments. The application of the current JAERI's X-ray reference field constructed in accordance with the Japanese Standards should be limited for domestic purposes becase of the characterization technique different from the International Standards. Therefore,for application to international performance tests, X-ray reference fields in the narrow,wide and high air-kerma series based on the International Standards were established using the medium-hard X-ray generator of the Facility of Radiation Standards(FRS), JAERI. This report presents quality characterization, estimation of X-ray spectra of each dose units of the new FRS's fields,and comparison of the qualities and the X-ray spectra to those of the ISO's. The FRS's qualities show good agreement with ISO's: the reference fields should serve for performance tests for international radiation protection purposes.
Krot, N. N.*; Saeki, Masakatsu
JAERI-Review 2003-005, 37 Pages, 2003/03
The original manuscript was prepared by Professor N. N. Krot of Institute of Physical Chemistry, Russian Academy of sciences, in 1997. Saeki tried to translate that into Japanese and to add some new data since 1997. The contents include the whole picture of cation-cation interactions mainly on 5-valence neptunium compounds. Firstly, characteristic structures are summarized for the cation-cation bonding in compounds of neptunium. Secondly, it is introduced how the cation-cation bonding affects physical and chemical properties of the compounds. Then, detection-methods are shown for the cation-cation bonding in the compounds. Besides, the cation-cation interaction are shortly reviewed for compounds of other actinide-ions.
Purazuma, Kaku Yugo Gakkai-Shi, 78(9), p.913 - 924, 2002/09
An introductory review is given on recent developments in the methods for stability analysis of a toroidally confined plasma. Emphasis is put on the perturbation analysis of a magnetohydrodynamic system that has the marginally stable state as a terminal point of continuous spectra. We address ourselves to the asymptotic matching method pertinent to such a problem. The Newcomb equation and inner-layer equations are essential ingredients in the methods and the numerical methods for solving them are discussed.
Nagano, Tetsushi; Isobe, Hiroshi*; Nakashima, Satoru*; Ashizaki, Midori*
Applied Spectroscopy, 56(5), p.651 - 657, 2002/05
no abstracts in English
Iemura, K.*; Otani, Shunsuke*; Suzuki, H.*; Takeda, Junichi*; Machida, Shuichi*; Tanabe, K.*; Takayanagi, Toshinobu*; Wakiya, K.*; Sekiguchi, M.*; Kanai, Yasuyuki*; et al.
Physical Review A, 64(6), p.062709_1 - 062709_14, 2001/12
We measured ejected electron spectra caused by autoionization of doubly excited states in He atoms; the excited He was made by double electron capture of low-energy He ions colliding with Ba atoms. Measurements were performed by means of zero degree electron spectroscopy at projectile energies from 40 to 20 keV. Electron spectra due to autoionization from the states He(2lnl) to He+(1s) for n2, and those from He(3lnl) to He(2s or 2p) for n3, were observed. Line peaks in the spectra were identified by comparing observed electron spectra with those of several theoretical calculations. It was found that doubly excited states of relatively high angular momenta such as the D and F terms were conspicuously created in a quite different manner from the cases of the production of doubly excited states by the use of photon, electron, or ion impacts on neutral He atoms. Rydberg states with large n values were observed with high population in both the He(2lnl) and He(3lnl) series.
Kurata, Yuji; Itabashi, Yukio; Mimura, Hideaki*; Kikuchi, Taiji; Amezawa, Hiroo; Shimakawa, Satoshi; Tsuji, Hirokazu; Shindo, Masami
Journal of Nuclear Materials, 283-287(Part.1), p.386 - 390, 2000/12
no abstracts in English
Ioka, Ikuo; Yonekawa, Minoru; Miwa, Yukio; Mimura, Hideaki; Tsuji, Hirokazu; Hoshiya, Taiji
Journal of Nuclear Materials, 283-287(Part.1), p.440 - 445, 2000/12
no abstracts in English