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Journal Articles

Measurements of the $$^{243}$$Am neutron capture and total cross sections with ANNRI at J-PARC

Kimura, Atsushi; Nakamura, Shoji; Terada, Kazushi*; Nakao, Taro*; Mizuyama, Kazuhito*; Iwamoto, Nobuyuki; Iwamoto, Osamu; Harada, Hideo; Katabuchi, Tatsuya*; Igashira, Masayuki*; et al.

Journal of Nuclear Science and Technology, 56(6), p.479 - 492, 2019/06

Journal Articles

Measurements of neutron total and capture cross sections of $$^{241}$$Am with ANNRI at J-PARC

Terada, Kazushi*; Kimura, Atsushi; Nakao, Taro*; Nakamura, Shoji; Mizuyama, Kazuhito*; Iwamoto, Nobuyuki; Iwamoto, Osamu; Harada, Hideo; Katabuchi, Tatsuya*; Igashira, Masayuki*; et al.

Journal of Nuclear Science and Technology, 55(10), p.1198 - 1211, 2018/10

 Times Cited Count:1 Percentile:38.14(Nuclear Science & Technology)

Journal Articles

Resonance analysis of cross section data measured by J-PARC/MLF using the modified REFIT code

Mizuyama, Kazuhito; Iwamoto, Nobuyuki; Iwamoto, Osamu; Terada, Kazushi; Nakao, Taro

JAEA-Conf 2017-001, p.163 - 168, 2018/01

Journal Articles

Application of modified REFIT code for J-PARC/MLF to evaluation of neutron capture cross section on $$^{155,157}$$Gd

Mizuyama, Kazuhito; Iwamoto, Nobuyuki; Iwamoto, Osamu; Hasemi, Hiroyuki*; Kino, Koichi*; Kimura, Atsushi; Kiyanagi, Yoshiaki*

EPJ Web of Conferences (Internet), 146, p.11042_1 - 11042_4, 2017/09

 Percentile:100

Gadolinium has been used as neutron-absorbing material in a thermal reactor since $$^{155,157}$$ have large thermal neutron capture cross sections. Nevertheless, there is a discrepancy between RPI data and JENDL-4.0 data for $$^{157}$$Gd. The criticality in the reactor is very sensitive to the capture cross section. The RPI data made the criticality of Gd-loaded thermal systems in ICSBEP overestimated. Recently, the neutron capture cross sections of $$^{155,157}$$Gd were measured by the neutron time-of-flight (TOF) method using the Accurate Neutron-Nucleus Reaction measurement Instrument (ANNRI) in the J-PARC/MLF. The pulsed neutron beam from the Japan Spallation Neutron Source (JSNS) was used with a double-bunch structure in this measurement, since the incident proton beam is normally delivered in a double-bunch scheme in the J-PARC. In addition to this, it is necessary to take into account the energy resolution of the pulsed neutron beam at the JSNS for the accurate derivation of resolved resonance parameters. In this study, using the least-squares multilevel R-matrix code REFIT modified to include the double bunch structure and the resolution function for the ANNRI, we fitted the calculated capture cross sections of $$^{155,157}$$Gd to the experimental data at the ANNRI. We derived the resonance parameters for some low-lying resonances of the two Gd isotopes.

Journal Articles

Research and development for accuracy improvement of neutron nuclear data on minor actinides

Harada, Hideo; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kimura, Atsushi; Terada, Kazushi; Nakao, Taro; Nakamura, Shoji; Mizuyama, Kazuhito; Igashira, Masayuki*; Katabuchi, Tatsuya*; et al.

EPJ Web of Conferences (Internet), 146, p.11001_1 - 11001_6, 2017/09

 Times Cited Count:1 Percentile:14.04

Journal Articles

Correction of the thermal neutron capture cross section of $$^{241}$$Am obtained by the Westcott convention

Mizuyama, Kazuhito; Iwamoto, Nobuyuki; Iwamoto, Osamu

Journal of Nuclear Science and Technology, 54(1), p.74 - 80, 2017/01

Journal Articles

Development of evaluation method for improvement of nuclear data accuracy in MA isotopes

Mizuyama, Kazuhito; Iwamoto, Nobuyuki; Iwamoto, Osamu

JAEA-Conf 2016-004, p.35 - 39, 2016/09

Improvement of the accuracy of neutron nuclear data for minor actinides (MAs) is required for the nuclear transmutation technique. The purpose of our study is development of evaluation method for improvement of nuclear data accuracy in MA isotopes. For the accurate evaluation, it is necessary to find out the reason of the discrepancy in previous data, to development of the accurate analysis method of the resonance parameters. So far, we found out the reason of the discrepancy of the thermal neutron capture cross section in previous measurements, and succeeded the correction. However the discrepancy of the resonance integral was not improved. The energy dependence of the epithermal neutron flux which has been used for the Cd ratio method can be different from the realistic experimental condition. This may be the reason for the discrepancy among the resonance integrals. For the accurate analysis of the resonance parameters, the precise resolution function's parameters are necessary. We are planning to obtain them by using the well-known stable nucleus and will apply them to the analysis of MAs.

Journal Articles

Importance of the neutron flux information to the evaluation of thermal neutron capture cross section and resonance integral of minor actinides

Mizuyama, Kazuhito; Iwamoto, Nobuyuki; Iwamoto, Osamu

Proceedings of International Conference on the Physics of Reactors; Unifying Theory and Experiments in the 21st Century (PHYSOR 2016) (USB Flash Drive), p.2437 - 2443, 2016/05

The accurate data of the minor actinides (MAs) is required for the nuclear waste problem. However, there is large discrepancy among the previous data. Especially such large discrepancy can been seen between the activation and the time-of-flight measurements. In the activation measurements, the Cd-ratio method based on the Westcott convention has been used in order to obtain the thermal neutron capture cross section $$sigma_0$$ and the resonance integral $$I_0$$ or the s-factor $$s_0$$. By reviewing the Westcott convention and the Cd-ratio method, we found that the large discrepancy of $$sigma_0$$ can be made smaller by introducing a correction term for the resonance integral or the s-factor in order to correct the contribution of the resonances near the Cd cut-off energy. However, the discrepancy of the resonance integral and the s-factor still remains. In the original Westcott convention, the epithermal component of the neutron flux has been supposed to be proportional to $$1/E$$, but it may not be true in the realistic condition of the neutron flux. Supposing $$1/E^{1+alpha}$$ for the epithermal component, we found that $$alpha$$ dependence is not negligible. For the fully consistent and more accurate evaluation of the previous activation measurements for MAs, the detailed information of the neutron flux is necessary and very important.

Journal Articles

Verification of the Cd-ratio method in $$^{241}$$Am using JENDL-4.0

Mizuyama, Kazuhito; Iwamoto, Nobuyuki; Iwamoto, Osamu

JAEA-Conf 2015-003, p.245 - 250, 2016/03

The management of the nuclear waste problem requires the high precision of the neutron capture cross section for minor actinides. One of the important reaction is the neutron capture reaction of $$^{241}$$Am. However, the thermal neutron capture cross section of $$^{241}$$Am is not optimized yet. Especially the values of thermal cross sections measured by the activation technique are around 20% bigger than the other methods (TOF, $$gamma$$ & $$alpha$$ spectroscopy etc.). In the activation method, the Westcott conventional representation and the Cd-ratio method are used for the analysis of the cross section. However, it may not work well due the special resonance structure of $$^{241}$$Am. In our study, we verify the Cd-ratio method using the JENDL-4.0, and try to correct the experimental cross section based on our verification of the Cd-ratio method. Consequently we obtained the very close value of the cross section to the JENDL-4.0.

Journal Articles

Accuracy improvement of neutron nuclear data on minor actinides

Harada, Hideo; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kimura, Atsushi; Terada, Kazushi; Nakao, Taro; Nakamura, Shoji; Mizuyama, Kazuhito; Igashira, Masayuki*; Katabuchi, Tatsuya*; et al.

EPJ Web of Conferences (Internet), 93, p.06001_1 - 06001_5, 2015/05

 Times Cited Count:3 Percentile:10.3

Improvement of accuracy of neutron nuclear data for minor actinides (MAs) and long-lived fission products (LLFPs) is required for developing innovative nuclear system transmuting these nuclei. In order to meet the requirement, the project entitled as "Research and development for Accuracy Improvement of neutron nuclear data on Minor ACtinides (AIMAC)" has been started as one of the "Innovative Nuclear Research and Development Program" at October 2013. The AIMAC project team is composed of researchers in four different fields: differential nuclear data measurement, integral nuclear data measurement, nuclear chemistry, and nuclear data evaluation. By integrating all of the forefront knowledge and techniques in these fields, the team aims at improving the accuracy of the data. The background, overall plan, and recent progress of the AIMAC project will be reviewed.

Oral presentation

R&D for accuracy improvement of neutron nuclear data on minor actinides, 10; High quality evaluation via bouncing ideas off measurement and evaluation

Iwamoto, Osamu; Iwamoto, Nobuyuki; Mizuyama, Kazuhito

no journal, , 

Under Innovative Nuclear Research and Development Program, "R&D for accuracy improvement of neutron nuclear data on minor actinides", present status of measurements and evaluations for MA nuclear data has been reviewed for "High quality evaluation via bouncing ideas off measurement and evaluation". The important MAs of Np-237 and Am-241, 243 were investigated in the thermal to fast neutron region. It was found that measured data for the thermal neutron cross sections of Np-237 and Am-241 were converging to a value with 5 to 6% discrepancies. The errors in evaluated nuclear data library were checked by comparing with the experimental data. Data for important FPs of Tc-99, I-129 etc. were also reviewed. In this presentation, a plan and result of review for a part of nuclear data evaluation of the program will be reported.

Oral presentation

R&D for accuracy improvement of neutron nuclear data on minor actinides, 1; Research plan of AIMAC project

Harada, Hideo; Iwamoto, Osamu; Nakamura, Shoji; Kimura, Atsushi; Iwamoto, Nobuyuki; Terada, Kazushi; Nakao, Taro; Mizuyama, Kazuhito; Igashira, Masayuki*; Katabuchi, Tatsuya*; et al.

no journal, , 

The research project has been started for improving accuracy of neutron nuclear data for minor actinides (MAs) and long-lived fission products (LLFPs), which is required for developing innovative nuclear system transmuting these nuclei. The project consists of 5 items: (1) Accurate measurements of thermal neutron capture cross-sections (2) High-precision quantification of sample amount used for TOF measurement (3) Resonance parameter determination by combining total and capture cross sections (4) Extension of capture cross sections to high energy neutrons (5) High quality evaluation based on iterative communication with experimenters. The overall plan of the project is presented.

Oral presentation

R&D for accuracy improvement of neutron nuclear data on minor actinides

Harada, Hideo; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kimura, Atsushi; Terada, Kazushi; Nakao, Taro; Nakamura, Shoji; Mizuyama, Kazuhito; Igashira, Masayuki*; Katabuchi, Tatsuya*; et al.

no journal, , 

Improvement of accuracy of neutron nuclear data for minor actinides (MAs) and long-lived fission products (LLFPs) is required for developing innovative nuclear system transmuting these nuclei. In order to meet the requirement, the project entitled as "Research and development for Accuracy Improvement of neutron nuclear data on Minor ACtinides (AIMAC)" has been started as one of the "Innovative Nuclear Research and Development Program" at October 2013. The background, overall plan, and expected achievements of the AIMAC project will be reviewed.

Oral presentation

Evaluation of the thermal neutron capture cross section of $$^{241}$$Am

Mizuyama, Kazuhito; Iwamoto, Nobuyuki; Iwamoto, Osamu

no journal, , 

The accuracy of nuclear data for the minor actinides (MAs) included in the high level radioactive wastes which have the long term radiotoxicity is required to be improved for the environmental load reduction technique. However, there is large discrepancy among the previous measurements for MAs. The Cadmium(Cd)-ratio method is the analysis method to deduce the $$sigma_0$$ and the s-factor by using the Cd-ratio given by the reaction rates without(with) the Cd-filter. The s-factor is defined by the normalized resonance integral by $$sigma_0$$ after subtracting 1/v component. Since there are lower resonances than the cut-off energy in $$^{241}$$Am, it is necessary to correct the effect of them in order to deduce the $$sigma_0$$ accurately. In this study, we evaluated the effect of the lower resonances than the cut-off energy as the correction of s-factor from the JENDL-4.0, and corrected the existing the data. As a result, the consistency among the measurements was improved.

Oral presentation

Measurements of neutron total and capture cross sections of Am-241

Terada, Kazushi; Nakao, Taro; Kimura, Atsushi; Nakamura, Shoji; Mizuyama, Kazuhito; Iwamoto, Nobuyuki; Iwamoto, Osamu; Harada, Hideo

no journal, , 

Measurements of the neutron total and capture cross sections of Am-241 have been performed using a time-of-flight method with a Li-glass detector and Ge spectrometers located on the ANNRI of the MLF in the J-PARC. The neutron total cross sections of Am-241 were determined in the neutron energy region from 4 meV to 2 eV. Comparisons of the present result with previous experimental data and evaluations were made. This contribution presents the obtained results.

Oral presentation

R&D for accuracy improvement of neutron nuclear data on minor actinides, 8; Evaluation of neutron capture cross sections on MA and $$^{99}$$Tc

Iwamoto, Nobuyuki; Mizuyama, Kazuhito; Iwamoto, Osamu

no journal, , 

no abstracts in English

Oral presentation

R&D for accuracy improvement of neutron nuclear data on minor actinides, 3; Measurements of neutron capture cross sections of $$^{241}$$Am with ANNRI at J-PARC

Terada, Kazushi; Nakao, Taro; Kimura, Atsushi; Nakamura, Shoji; Mizuyama, Kazuhito; Iwamoto, Nobuyuki; Iwamoto, Osamu; Harada, Hideo

no journal, , 

Measurements of neutron capture cross sections of $$^{241}$$Am have been performed with Ge spectrometers at ANNRI in the J-PARC. We obtained capture cross sections of $$^{241}$$Am in neutron energy region from the thermal to 100 eV. The results were compared with previous measurements and evaluations.

Oral presentation

R&D for accuracy improvement of neutron nuclear data on minor actinides, 1; A Summary of progress in the AIMAC project

Harada, Hideo; Iwamoto, Osamu; Iwamoto, Nobuyuki; Kimura, Atsushi; Terada, Kazushi; Nakao, Taro; Nakamura, Shoji; Mizuyama, Kazuhito; Igashira, Masayuki*; Katabuchi, Tatsuya*; et al.

no journal, , 

To improve accuracy of neutron nuclear data on minor actinides, a Japanese nuclear data project entitled as "Research and development for Accuracy Improvement of neutron nuclear data on Minor ACtinides (AIMAC)" has been performed by integrating all of the forefront knowledge and techniques in four different fields, such as, differential nuclear data measurement, integral nuclear data measurement, nuclear chemistry, and nuclear data evaluation. Highlights of the AIMAC project and their impacts are outlined.

18 (Records 1-18 displayed on this page)
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