Neutron total and capture cross-section measurements of Gd and Gd in the thermal energy region with the Li-glass detectors and NaI(Tl) spectrometer installed in J-PARCMLFANNRI

木村 敦; 中村 詔司; 遠藤 駿典; Rovira Leveroni, G.; 岩本 修; 岩本 信之; 原田 秀郎; 片渕 竜也*; 寺田 和司*; 堀 順一*; et al.

Journal of Nuclear Science and Technology, 60(6), p.678 - 696, 2023/06

https://doi.org/10.1080/00223131.2022.2134224

Neutron total and capture cross-section measurements of Gd and Gd were performed in the ANNRI at the MLF of the J-PARC. The neutron total cross sections were determined in the energy region from 5 to 100 meV. At the thermal neutron energy, the total cross sections were obtained to be 59.41.7 and 251.94.6 kilobarn for Gd and Gd, respectively. The neutron capture cross sections were determined in the energy region from 3.5 to 100 meV with an innovative method by taking the ratio of the detected capture event rate between thin and thick samples. At the thermal energy, the capture cross sections were obtained as 59.02.5 and 247.43.9 kilobarn for Gd and Gd, respectively. The present total and capture cross sections agree well within the standard deviations. The results for Gd were found to be consistent with the values in JENDL-4.0 and the experimental data given by Mastromarco et al. and Leinweber et al. within one standard deviation. Moreover, the present results for Gd agreed with the evaluated data in JENDL-4.0 and the experimental data by Mller et al. within one standard deviation and agreed with the data by Mastromarco et al. within 1.4 standard deviations. However, they disagree (11% larger) with the experimental result by Leinweber et al.

Simultaneous evaluation of uranium and plutonium fast neutron fission cross sections up to 200 MeV for JENDL-5 and its updates

大塚 直彦*; 岩本 修

EPJ Web of Conferences, 284, p.08011_1 - 08011_4, 2023/05

https://doi.org/10.1051/epjconf/202328408011

The fast neutron fission cross sections of U and Pu were evaluated for the JENDL-5 library up to 200 MeV. The experimental fission cross sections and their ratios in the EXFOR library were reviewed with the source articles. Additionally, Poenitz's data compiled in his GMA database were reviewed. We found about 0 datasets are archived with the uncertainty information sufficient for covariance matrix construction and converted them from EXFOR to an experimental database with their covariance matrices. When the uncertainty information in the source article is missing in the EXFOR entry, we updated the EXFOR entry. We minimized corrections to the experimental database to make our evaluation becomes traceable. The least-squares fitting was performed to the logarithms of the cross sections and their rations in the experimental database by using the simultaneous least-squares fitting code SOK. The best precisions of the group-wise cross sections were achieved around 2 to 3 MeV, where the external uncertainties are 1% (U), 1.5% (U, Pu) or 2.5% (Pu). Well documented experimental fission cross sections are desired for U between 100 and 300 keV and Pu in the whole energy range since the numbers of the usable experimental datasets are limited and it makes the uncertainties in our evaluation relatively high. The evaluated cross sections were also validated against the spectrum averaged fission cross sections measured under the Cf and - neutron fields, and we found the newly evaluated cross sections are consistent with the experimental spectrum averaged cross sections well except for U fission cross sections measured in the Cf neutron fields, which is underestimated by the newly evaluated cross sections as well as those in many other data libraries.

Am neutron capture cross section in the keV region using Si and Fe-filtered neutron beams

Rovira Leveroni, G.; 木村 敦; 中村 詔司; 遠藤 駿典; 岩本 修; 岩本 信之; 片渕 竜也*; 児玉 有*; 中野 秀仁*

Journal of Nuclear Science and Technology, 60(5), p.489 - 499, 2023/05

https://doi.org/10.1080/00223131.2022.2116496

The neutron capture cross-section of Am was measured in the keV neutron range using the recently implemented neutron filtering system of the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) beamline in the Materials and Life Science (MLF) facility of the Japan Proton Accelerator Research Complex (J-PARC). Filter arrays consisting of 20 cm of Fe and Si were employed in separate measurements to provide filtered neutron beams with averaged neutron energies of 23.5 (Fe), 51.5 and 127.7 (Si) keV. The present Am results were obtained relative to the Au neutron capture yield by applying the total energy detection principle together with the pulse-height weighting technique. The Am neutron capture cross section was determined as 2.72 0.29 b at 23.5 keV, 2.14 0.26 b at 51.5 keV and 1.32 0.10 b at 127.7 keV with total uncertainties in the range of 8 to 12, much lower in comparison to the latest time-of-flight experimental data available.

Evaluation of covariance data in JENDL

岩本 修

EPJ Web of Conferences, 281, p.00009_1 - 00009_4, 2023/03

https://doi.org/10.1051/epjconf/202328100009

Evaluation of covariance data for JENDL virtually started after the release of JENDL-3.2. Covariance data were estimated for 16 nuclides in JENDL-3.2 and compiled as JENDL-3.2 Covariance File. For JENDL-4.0, covariance evaluation was much enhanced especially for actinides; the number of nuclides with covariance was 99. With the new evaluations for light nuclides and structure materials, the latest version JENDL-5 provides covariance data for 105 nuclides. The covariances in JENDL were basically evaluated with the least square method with available experimental data. Basic methods were developed at the time of JENDL-3.2 covariance evaluation. While the nuclear reaction modeling codes were changed from the JENDL-3.2 evaluation to the JENDL-4.0 or JENDL-5 evaluations, the covariance evaluation code has been continuously used for all of them. Overview of the covariance evaluation for JENDL will be presented.

Fast-neutron capture cross section data measurement of minor actinides for development of nuclear transmutation systems

片渕 竜也*; 岩本 修; 堀 順一*; 木村 敦; 岩本 信之; 中村 詔司; Rovira Leveroni, G.; 遠藤 駿典; 芝原 雄司*; 寺田 和司*; et al.

EPJ Web of Conferences, 281, p.00014_1 - 00014_4, 2023/03

https://doi.org/10.1051/epjconf/202328100014

Long-lived minor actinides (MA) in nuclear waste from nuclear power plants are a long-standing issue to continue nuclear energy production. To solve the issue, researchers have suggested nuclear transmutation, in which long-lived radionuclides are transmuted into stable or shorter-life nuclides via neutron-induced nuclear reactions. Development of nuclear transmutation systems as an accelerator-driven system requires accurate neutron nuclear reaction data. The present research project entitled "Study on accuracy improvement of fast-neutron capture reaction data of long-lived MAs for development of nuclear transmutation systems" have been conducted as a joint collaboration, including Tokyo Tech, Japan Atomic Energy Agency and Kyoto University. This project focuses on the neutron capture reaction of MAs, especially Np, Am and Am, in the fast neutron energy region. The final goal of this project is to improve the accuracies of the neutron capture cross sections of Np, Am and Am employing a high-intensity neutron beam from a spallation source of the Japan Proton Accelerator Research Complex (J-PARC) that reduces uncertainties of measurement. To achieve the goal, a neutron beam filter system in J-PARC, sample characteristic assay, and theoretical reaction model study were developed. In this contribution, the overview and results of the project will be presented.

Collaboration with Dr. Efrem Sh. Soukhovitsukii; Our fortuitous experiences on optical model analysis, his contribution to nuclear data activities of Japan and a posthumous study on light-nuclei

国枝 賢; 岩本 修; 深堀 智生; 千葉 敏*

European Physical Journal A, 59(1), p.2_1 - 2_8, 2023/01

https://doi.org/10.1140/epja/s10050-022-00907-3

原子核の変形並びに回転や振動を記述する軟回転体模型を構築し、チャンネル結合法に基づいて核構造の情報を光学模型に取り入れたことは故Soukhovitsukii博士の偉大な成果である。また、博士と原子力機構との共同研究により得られた数々の光学模型解析結果やOPTMANコードは日本の核データライブラリJENDLの開発に多大なる貢献を果たした。本論文では、主に軟回転体模型による核構造解析や光学模型本シャルについての同氏との共同研究成果をレビューする。また、軽原子核に対する原子核の変形と断面積の関係や模型の適用限界など、同氏の没後に得られた新たな解析結果を報告する。

Japanese Evaluated Nuclear Data Library version 5; JENDL-5

岩本 修; 岩本 信之; 国枝 賢; 湊 太志; 中山 梓介; 安部 豊*; 椿原 康介*; 奥村 森*; 石塚 知香子*; 吉田 正*; et al.

Journal of Nuclear Science and Technology, 60(1), p.1 - 60, 2023/01

https://doi.org/10.1080/00223131.2022.2141903

The fifth version of Japanese Evaluated Nuclear Data Library, JENDL-5, was developed. JENDL-5 aimed to meet a variety of needs not only from nuclear reactors but also from other applications such as accelerators. Most of the JENDL special purpose files published so far were integrated into JENDL-5 with revisions. JENDL-5 consists of 11 sublibraries: (1) Neutron, (2) Thermal scattering law, (3) Fission product yield, (4) Decay data, (5) Proton, (6) Deuteron, (7) Alpha-particle, (8) Photonuclear, (9) Photo-atomic, (10) Electro-atomic, and (11) Atomic relaxation. The neutron reaction data for a large number of nuclei in JENDL-4.0 were updated ranging from light to heavy ones, including major and minor actinides which affect nuclear reactor calculations. In addition, the number of nuclei of neutron reaction data stored in JENDL-5 was largely increased; the neutron data covered not only all of naturally existing nuclei but also their neighbor ones with half-lives longer than 1 day. JENDL-5 included the originally evaluated data of thermal scattering law and fission product yield for the first time. Light charged-particle and photon induced reaction data were also included for the first time as the JENDL general purpose file.

Am neutron capture cross section measurement and resonance analysis

Rovira Leveroni, G.; 木村 敦; 中村 詔司; 遠藤 駿典; 岩本 修; 岩本 信之; 片渕 竜也*; 児玉 有*; 中野 秀仁*; 佐藤 八起*

JAEA-Conf 2022-001, p.91 - 96, 2022/11

https://doi.org/10.11484/jaea-conf-2022-001

Neutron capture cross section measurements were performed in the Accurate Neutron Nucleus Reaction Measurement Instrument (ANNRI) at the Materials and Life Science Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC). The time-of-flight (TOF) methodology was employed in a non-filter condition experiment to determine the neutron capture cross section from thermal to about 100 eV. Moreover, experiments were performed using the neutron filtering system to determine the neutron capture cross section at the energy of 23.5 keV using Fe as filter material. In this study, the preliminary results of the Am neutron capture cross section from 10 meV to about 100 eV determined in TOF experiments and at 23.5 keV from Fe filter experiments are presented. In the TOF experiments, the Am neutron capture cross section was normalized by means of the saturated resonance method using a Au sample with a mass of 1.5 g. In addition, for the Fe filter experiments, the capture cross section of Am at the energy of 23.5 keV was determined relative to the Au yield obtained from a measurement using the same Au sample. Moreover, early-stage results of a resonance analysis of the Am capture resonances are also presented.

EXFOR-based simultaneous evaluation of neutron-induced uranium and plutonium fission cross sections for JENDL-5; Inputs and outputs

大塚 直彦*; 岩本 修

JAEA-Data/Code 2022-005, 102 Pages, 2022/10

JAEA-Data-Code-2022-005.pdf:2.18MB
JAEA-Data-Code-2022-005-appendix(CD-ROM).zip:3.85MB

UとPuの10keVから200MeVの中性子入射核分裂断面積、およびUとPuの100keVから200MeVまでの中性子入射核反応断面積をJENDL-5のために同時評価した。実験断面積とその比の対数をシュミットロスの屋根関数(Schmittroth's roof function)の線形結合で表現し、その係数を最小二乗法により決定した。同時評価コードSOKを規格化が任意の実験値に拡張したものを本評価に用いた。本報告書は(1)実験データベースの構築、(2)ドレスデン工科大学(TUD)・ラジウム研究所(KRI)の共同測定で得られたデータの選定、(3)本評価で得られた断面積の最近の主なライブラリとの比較、(4)1970年代に測定された235Uデータの影響、について述べる。

Calculation of recoil nucleus spectrum in the presence of multi-particle emission in nuclear reaction with Monte Carlo method as an extension of CCONE code

岩本 修

Journal of Nuclear Science and Technology, 59(10), p.1232 - 1241, 2022/10

https://doi.org/10.1080/00223131.2022.2038300

Application of Monte Carlo method was proposed for the calculations of recoil nucleus spectra on high energy nuclear reactions, in which velocity distributions were integrated over 3 dimensional space with taking into account multi-particle emissions. It was implemented on a nuclear reaction model code CCONE. The results of double differential cross sections of recoil nuclei from a proton induced reaction on C were compared with the experimental data and the results of a Monte Carlo simulation code PHITS. It was found that the present results show reasonably good agreements with the experimental data for almost all measured recoil nuclei. The results are also compared with the data of evaluated nuclear data libraries of ENDF/B-VIII.0 and TENDL-2017. While the average energies of the recoil nuclei are similar, significant differences are observed in the energy distributions.