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.

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.

KeV-neutron capture cross-section measurement of Au with a Cr-filtered neutron beam at the ANNRI beamline of MLF/J-PARC

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*; et al.

Journal of Nuclear Science and Technology, 59(5), p.647 - 655, 2022/05

https://doi.org/10.1080/00223131.2021.1997666

Cr-filtered keV-neutron experiments were performed in 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) to measure the neutron capture cross-section of Au. The energy range of the neutron filtering system at ANNRI was extended through the use of 15 cm of Cr as filter material to tailor quasi-monochromatic neutron peaks with averaged neutron energies of 133.4 and 45.0 keV. The performance of the Cr filter assembly was evaluated by means of experimental capture and transmission analyses, together with the use of Monte-Carlo simulations. The present Au neutron capture cross-section results provide agreement within uncertainties with the JENDL-4.0 standard evaluated library and the IAEA standard data library further demonstrating the capabilities of the neutron filtering system at ANNRI.

Feasibility study of PGAA for boride identification in simulated melted core materials

土川 雄介; 阿部 雄太; 大石 佑治*; 甲斐 哲也; 藤 暢輔; 瀬川 麻里子; 前田 亮; 木村 敦; 中村 詔司; 原田 正英; et al.

JPS Conference Proceedings (Internet), 33, p.011074_1 - 011074_6, 2021/03

https://doi.org/10.7566/JPSCP.33.011074

福島原子力発電所の解体作業では、溶融した燃料棒に含まれるホウ素分布を事前に把握することが重要である。溶融燃料棒の模擬試験体を用意し、ホウ素やホウ化物の含有量を調査する研究が行われてきた。本研究では、その一環として中性子を用いたホウ素並びにホウ化物分布の測定技術開発を行った。ホウ素の中性子吸収に伴う即発ガンマ線を測定し、ホウ素量や二次元分布を測定した。また、n(B,)反応における478keV線は、ホウ素の化合状態により、線ピークの幅が変化することが知られている。このことを用い、特に溶融燃料棒周辺に存在することが予測されているZrBやFeBといったホウ化物の識別可能性について調査した。測定はJ-PARC/MLFのANNRI, NOBORU, RADENにて行った。これらの解析結果について報告する。

Production of and mesons in UU collisions at GeV

Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他397名*

Physical Review C, 102(6), p.064905_1 - 064905_13, 2020/12

https://doi.org/10.1103/PhysRevC.102.064905

The PHENIX experiment at the Relativistic Heavy Ion Collider measured and mesons at midrapidity in UU collisions at GeV in a wide transverse momentum range. Measurements were performed in the decay modes. A strong suppression of and meson production at high transverse momentum was observed in central UU collisions relative to binary scaled results. Yields of and mesons measured in UU collisions show similar suppression pattern to the ones measured in AuAu collisions at GeV for similar numbers of participant nucleons. The / ratios do not show dependence on centrality or transverse momentum, and are consistent with previously measured values in hadron-hadron, hadron-nucleus, nucleus-nucleus, and collisions.

Measurement of jet-medium interactions via direct photon-hadron correlations in Au+Au and +Au collisions at GeV

Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他572名*

Physical Review C, 102(5), p.054910_1 - 054910_11, 2020/11

https://doi.org/10.1103/PhysRevC.102.054910

We present direct photon-hadron correlations in 200 GeV/A AuAu, Au and collisions, for direct photon from 5 - 12 GeV/, collected by the PHENIX Collaboration in the years from 2006 to 2011. We observe no significant modification of jet fragmentation in Au collisions, indicating that cold nuclear matter effects are small or absent. Hadrons carrying a large fraction of the quark's momentum are suppressed in AuAu compared to and Au. As the momentum fraction decreases, the yield of hadrons in AuAu increases to an excess over the yield in collisions. The excess is at large angles and at low hadron and is most pronounced for hadrons associated with lower momentum direct photons. Comparison to theoretical calculations suggests that the hadron excess arises from medium response to energy deposited by jets.

Polarization and cross section of midrapidity production in collisions at GeV

Acharya, U.*; 長谷川 勝一; 今井 憲一*; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他344名*

Physical Review D, 102(7), p.072008_1 - 072008_13, 2020/10

https://doi.org/10.1103/PhysRevD.102.072008

The PHENIX experiment has measured the spin alignment for inclusive decays in collisions at GeV at midrapidity. The angular distributions have been measured in three different polarization frames, and the three decay angular coefficients have been extracted in a full two-dimensional analysis. Previously, PHENIX saw large longitudinal net polarization at forward rapidity at the same collision energy. This analysis at midrapidity, complementary to the previous PHENIX results, sees no sizable polarization in the measured transverse momentum range of GeV/. The results are consistent with a previous one-dimensional analysis at midrapidity at GeV. The transverse-momentum-dependent cross section for midrapidity production has additionally been measured, and after comparison to world data we find a simple logarithmic dependence of the cross section on .

VHTR technology development in Japan; Progress of R&D activities for GIF VHTR system

柴田 大受; 佐藤 博之; 植田 祥平; 竹上 弘彰; 高田 昌二; 國富 一彦

2018 GIF Symposium Proceedings (Internet), p.99 - 106, 2020/05

第四世代原子力システムの一つである超高温ガス炉(VHTR)システムについて、原子力研究開発機構で実施している研究開発活動の進捗についてまとめた。高温工学試験研究炉(HTTR)は2010年に原子炉出口温度950Cでの50日間連続運転を達成し、その際、被覆粒子燃料の優れた品質を示した。また、高燃焼度化に向けてZrC被覆粒子の開発を進めている。炉内の構造物に用いる黒鉛の耐酸化性の向上のため、黒鉛へのSiC被覆について中性子照射の影響を調べている。将来の商用高温ガス炉コジェネレーションシステムについて、国際的な安全基準の整備を進めている。HTTRは新規制基準の適合性審査を経て、2019年に再稼働を見込んでいる。ISプロセス連続水素製造試験設備では、2016年に31時間の連続試験が完了した。HTTRでの水素製造-ガスタービン試験に向けた基本設計を完了した。

The Deposition densities of radiocesium and the air dose rates in undisturbed fields around the Fukushima Dai-ichi Nuclear Power Plant; Their temporal changes for five years after the accident

三上 智; 田中 博幸*; 松田 秀夫*; 佐藤 昭二*; 星出 好史*; 奥田 直敏*; 鈴木 健夫*; 坂本 隆一*; 安藤 正樹; 斎藤 公明

Journal of Environmental Radioactivity, 210, p.105941_1 - 105941_12, 2019/12

AA2019-0019.pdf:2.65MB

https://doi.org/10.1016/j.jenvrad.2019.03.017

2011年から2016年にかけて福島第一原子力発電所から80km圏内の撹乱のない多数の測定点で放射性セシウムの沈着量と空間線量率を繰り返し測定し、それらの経時変化の特徴を明らかにした。この地域のバックグラウンド放射線量を除いた平均空間線量率は、2011年6月から2016年8月までの期間中に初期の約20%に減少した。これは主にCs(半減期2.06y)の壊変の結果である。空間線量率の減少は放射性セシウムの壊変から予想されるものよりも約2倍早く、この減少の大部分は放射性セシウムの土壌への浸透によるものである。除染されていない土壌におけるCsとCsの平均沈着量は、ほぼ放射性壊変から予想されるペースで減少していた。すなわち水平方向の放射性セシウムの移動が比較的小さいことを示した。空間線量率と沈着量の測定結果では除染の効果が明らかに観察された。測定点の平均空間線量率は、その詳細な定量分析は今後の課題だが、除染やその他の人間の活動によって約20%減少した。

Measurement of two-particle correlations with respect to second- and third-order event planes in AuAu collisions at GeV

Adare, A.*; 長谷川 勝一; 今井 憲一; 永宮 正治*; 佐甲 博之; 佐藤 進; 谷田 聖; PHENIX Collaboration*; 他451名*

Physical Review C, 99(5), p.054903_1 - 054903_29, 2019/05

AA2019-0567.pdf:3.42MB

https://doi.org/10.1103/PhysRevC.99.054903

We present measurements of azimuthal correlations of charged hadron pairs in GeV AuAu collisions after subtracting an underlying event using a model that includes higher-order azimuthal anisotropy , , and . After subtraction, the away-side ( of the highest transverse-momentum trigger ( GeV/) correlations is suppressed compared to that of correlations measured in collisions. At the lowest associated particle , the away-side shape and yield are modified. These observations are consistent with the scenario of radiative-jet energy loss. For the lowest- trigger correlations, an away-side yield exists and we explore the dependence of the shape of the away-side within the context of an underlying-event model. Correlations are also studied differentially versus event-plane angle . The angular correlations show an asymmetry when selecting the sign of the trigger-particle azimuthal angle with respect to the event plane. This asymmetry and the measured suppression of the pair yield out of plane is consistent with a path-length-dependent energy loss. No dependence can be resolved within experimental uncertainties.