Harada, Hideo; Takayama, Naoki; Komeda, Masao
Journal of Physics Communications (Internet), 4(8), p.085004_1 - 085004_17, 2020/08
A new convention of epithermal neutron spectrum is formulated for improving accuracy of resonance integrals. The new type function is proposed as an approximating function of epithermal neutron spectrum based on calculations by the state-of-art Monte Carlo code MVP-3. Bias effects on determination of resonance integrals due to utilizing approximating functions of the traditional types and the new type are compared. The other bias effect is also investigated, which is caused by neglecting position dependence of a neutron spectrum inside an irradiation capsule. For demonstrating the bias effects due to these assumptions on neutron spectrum quantitatively in a practical case, the thermal neutron-capture cross section and resonance integral of Cs measured at a research reactor JRR-3 are re-evaluated. A superior property of the proposed new convention is discussed. The experimental method is proposed to determine the new shape factor introduced in the convention by a combinational use of triple flux monitors (Au, Co and Zr), and its analytical methodology is formulated.
Riyana, E. S.; Okumura, Keisuke; Terashima, Kenichi
Journal of Nuclear Science and Technology, 56(9-10), p.922 - 931, 2019/09
Ishikawa, Hirotaku*; Kai, Tetsuya; Sato, Hirotaka*; Kamiyama, Takashi*
Journal of Nuclear Science and Technology, 56(2), p.221 - 227, 2019/02
Oba, Yojiro*; Morooka, Satoshi; Oishi, Kazuki*; Suzuki, Junichi*; Takata, Shinichi; Sato, Nobuhiro*; Inoue, Rintaro*; Tsuchiyama, Toshihiro*; Gilbert, E. P.*; Sugiyama, Masaaki*
Journal of Applied Crystallography, 50(2), p.334 - 339, 2017/04
Kojima, Kensuke; Okumura, Keisuke; Kosako, Kazuaki*; Torii, Kazutaka*
JAEA-Research 2015-019, 90 Pages, 2016/01
At the decommissioning of light water reactors (LWRs), it is important to evaluate an amount of radioactivity in the ex-core structures such as a reactor containment vessel, radiation shieldings, and so on. It is thought that the leakage neutron spectra in these radioactivation regions, which strongly affect the induced radioactivity, would be changed by different reactor core configurations such as fuel assembly loading pattern and fuel burnups. This study was intended to evaluate these effects. For the purpose, firstly, partial neutron currents on the core surfaces were calculated for some core configurations. Then, the leakage neutron flux spectra in major radioactivation regions were calculated based on the provided currents. Finally, influence of the core configurations upon the neutron flux spectra was evaluated. As a result, it has been found that the influence is small on the spectrum shapes of neutron fluxes. However, it is necessary to pay attention to the facts that intensities of the leakage neutron fluxes are changed by the configurations and that intensities and spectrum shapes of the leakage neutron fluxes are changed depending on the angular direction around the core.
Kunieda, Satoshi; Ichihara, Akira
JAERI-Data/Code 2005-005, 33 Pages, 2005/09
The computer code, POD-P, was developed to calculate energy spectra and angular distributions of emitted particles for the neutron-induced preequiliblium nuclear reactions. The energy-differential cross sections are computed with the classical one-component exciton model for the nucleon and composite-particle emissions. Along with this, the semi-empirical exciton models are also used for the composite-particle emissions. The double-differential cross sections are derived from those model calculations plus the angular-distribution systematics. The computational method and explanation of input parameters are given with some output examples.
Tanimura, Yoshihiko; Saegusa, Jun; Yoshizawa, Michio; Yoshida, Makoto
Nuclear Instruments and Methods in Physics Research A, 547(2-3), p.592 - 600, 2005/08
The moderator structure of a neutron spectrometer was optimized with a Monte Carlo code of MCNP-4B. The spectrometer consists of a cylindrical moderator and a position-sensitive thermal neutron detector. It can obtain an energy spectrum from thermal neutron distribution along the cylindrical axis of the moderator. The structure of the moderator was improved by putting a low hydrogen density material in the front of a high hydrogen density one and inserting a neutron absorber which eliminated thermal neutrons diffusing in the moderator. These improvements make energy resolution of the spectrometer better especially for the low energy neutrons from a few tens to 100 keV. The designed spectrometer can be applied to the measurement of energy spectrum over a neutron energy range from a few keV to 20 MeV.
Sato, Tatsuhiko; Endo, Akira; Yamaguchi, Yasuhiro; Takahashi, Fumiaki
Radiation Protection Dosimetry, 110(1-4), p.255 - 261, 2004/09
For monitoring of neutron doses in high-energy accelerator facilities, we have developed a neutron-monitor detector applicable to energies from the thermal energy to 100 MeV. The detector is composed of a cylindrical (12.7 cm in diameter and 12.7 cm in length) liquid organic scintillator BC501A covered with Li+ZnS(Ag) sheets. Characteristics of this phoswitch-type detector were studied experimentally in moderated neutron fields of Am-Be and Cf sources, and in quasi-monoenergetic neutron fields of 40 and 70 MeV. It was found from the experiments that the detector is enough sensitive to both thermal and fast neutrons, and has an excellent property of pulse-shape discrimination between them. We concluded, therefore, that the detector can be used for monitoring of neutron doses over a wide energy range from the thermal to 100 MeV.
Saegusa, Jun; Tanimura, Yoshihiko; Yoshizawa, Michio; Yoshida, Makoto
Radiation Protection Dosimetry, 110(1-4), p.91 - 95, 2004/09
For the accurate estimation of neutron dose equivalents, it is important to calibrate dosemeters in the field whose energy spectrum is similar to that in the workplace. For the purpose, studies are made toward the built of the spectrum changeable neutron calibration fields with the Van-de-Graff accelerator in the FRS in JAERI. The fields are produced by bombarding proton or deuteron beam from the accelerator to suitable targets surrounded by quasi-cylindrical moderators and absorbers of various materials. In the fields, neutron spectra with wide range energy index should be provided with sufficient fluence rate for the calibration of dosemeters. The objectives and conceptual design of the fields are discussed here, followed by the test simulation results of neutron spectra produced by various arrangements of a target and moderators.
Endo, Akira; Kim, E.; Yamaguchi, Yasuhiro; Sato, Tatsuhiko; Yoshizawa, Michio; Tanaka, Susumu; Nakamura, Takashi; Rasolonjatovo, A. H. D.*
Journal of Nuclear Science and Technology, 41(Suppl.4), p.510 - 513, 2004/03
no abstracts in English
Shibata, Keiichi; Asami, Tetsuo*; Watanabe, Takashi*; Watanabe, Yukinobu*; Yamamuro, Nobuhiro*; Igashira, Masayuki*; Kitazawa, Hideo*
JAERI-Research 2003-021, 49 Pages, 2003/09
Evaluations of neutron nuclear data for medium-heavy nuclides were performed for JENDL-3.3. The present work was undertaken to remove the drawbacks of the previous library JENDL-3.2. Recent measurements and nuclear model calculations were taken into account to improve the accuracy of the evaluated data. The data on natural elements were not produced in order to solve a problem of the inconsistency between elemental and isotopic data except for carbon and vanadium in JENDL-3.3.
Tamura, Itaru; Aizawa, Kazuya; Harada, Masahide; Shibata, Kaoru; Maekawa, Fujio; Soyama, Kazuhiko; Arai, Masatoshi
Proceedings of ICANS-XVI, Volume 1, p.529 - 539, 2003/07
Moderator components of the McStas code have been created for the design of the spectrometers of JSNS. Three cryogenic moderators are adopted in JSNS, One is a coupled H moderator for high intensity experiments and other two are decoupled H with poisoned or unpoisoned for high resolution moderators. Monte Carlo simulations have turned out to be useful for design of neutron scattering instruments with high complexity. The software package McStas is selected for its own flexibility. Since the characteristics of neutron beams generated from moderators make influence on the performance of pulse neutron spectrometers, it is important to perform the simulation with neutron source component written precisely. Both Energy dependence of neutron spectrum and time structure of neutrons were calculated using NMTC/JAERI97 and MCNP4a codes.The simulation parameters, which describe the pulse shape as a function of time, are optimized. The creation of neutron source components viewed to coupled H moderator and viewed to decoupled H moderator of JSNS are reported.
Meigo, Shinichiro; Harada, Masahide; Takada, Hiroshi
Proceedings of ICANS-XVI, Volume 3, p.1059 - 1067, 2003/07
In the neutronics design for the J-PARC facilities, transport codes of NMTC/JAM, MCNPX and MARS are used. In order to confirm the predict ability for these codes, it is important to compare with the experiment result. For the validation of the source term of neutron, the calculations are compared with the experimental spectrum of neutrons produced from thick target. Although slightly disagreement exists, NMTC/JAM, MCNPX and MARS are in good agreement with the experiment within by a factor of 2.
Ando, Masaki; Nakano, Yoshihiro; Okajima, Shigeaki; Kawasaki, Kenji
Journal of Nuclear Materials, 319, p.126 - 130, 2003/06
Doppler effect experiments on resonance materials for ROX fuels were carried out to examine the calculation accuracy in the intermediate neutron spectrum using Fast Critical Assembly (FCA) at Japan Atomic Energy Research Institute. This study is the second phase of a series of the Doppler effect experiments on the resonance materials, which is following the measurements in the fast neutron spectrum. The Doppler effect was measured as the sample reactivity change between the heated and unheated samples. The cylindrical samples of the resonance materials such as erbium (Er), tungsten (W) and thorium (ThO) were used. The sample was heated up to 800C at the center of the FCA core. The Doppler effect measurements were analyzed using the SRAC 95 code system with the use of JENDL 3.2. The calculated values agreed with the experiment within the experimental error for the W and ThO samples, while the calculation overestimated the experiment for the Er sample about 10 %.
Shibata, Taiju; Kikuchi, Takayuki; Shimakawa, Satoshi
Reactor Dosimetry in the 21st Century, p.211 - 218, 2003/00
The High Temperature Engineering Test Reactor (HTTR) is the first HTGR in Japan with a maximum power of 30 MW. The construction of it was completed successfully in March 2002. The HTTR aims to perform irradiation studies at its very wide irradiation spaces at high temperatures. Although the creep behavior of materials is measured by the large standard size specimens at out-of-pile, small size ones are generally used for in-pile creep tests because of the irradiation capability of reactors. The I-I type irradiation equipment, the first rig for the HTTR, is to be used for the in-pile creep test on a stainless steel with the standard specimens. The rig can give big tensile loads of about 9.8 kN on them. The temperatures of 550 and 600C and the fast neutron fluence of 1.210n/m are the targets of the test. Prior to the in-pile creep test, the in-core irradiation properties at the irradiation region are to be obtained by the rig as the first irradiation test. This paper describes the dosimetry plan at the first irradiation test and the subsequent data assessment procedure.
Kim, E.; Endo, Akira; Yamaguchi, Yasuhiro; Yoshizawa, Michio; Tanaka, Susumu; Shiomi, T.*; Nakamura, Takashi*; Rasolonjatovo, D. R. D.*
JAERI-Tech 2002-041, 73 Pages, 2002/03
no abstracts in English
Nagao, Yoshiharu; Takemoto, Noriyuki; Takeda, Takashi
JAERI-Tech 2001-069, 83 Pages, 2001/10
no abstracts in English
Advanced Photon Source International Workshop on Radiation Safety at Synchrotron Radiation Sources, p.1 - 7, 2001/04
no abstracts in English
Shimakawa, Satoshi; Nagao, Yoshiharu; Fujiki, Kazuo
Reactor Dosimetry: Radiation Metrology and Assessment (ASTM STP 1398), p.244 - 251, 2001/00
no abstracts in English
Maekawa, Fujio; Wada, Masayuki*; Von-Moellendorff, U.*; Wilson, P. P. H.*; Ikeda, Yujiro
Fusion Engineering and Design, 51-52(Part.B), p.815 - 820, 2000/11
no abstracts in English