Characterization of bremsstrahlung and -rays of fuel debris

Matsumura, Taichi; Okumura, Keisuke; Fujita, Manabu*; Sakamoto, Masahiro; Terashima, Kenichi; Riyana, E. S.

Radiation Physics and Chemistry, 199, p.110298_1 - 110298_8, 2022/10

https://doi.org/10.1016/j.radphyschem.2022.110298

Geopolymer and ordinary Portland cement interface analyzed by micro-Raman and SEM

Cantarel, V.; Yamagishi, Isao

Journal of Nuclear Science and Technology, 59(7), p.888 - 897, 2022/07

https://doi.org/10.1080/00223131.2021.2016510

Development of the sintering solidification method for spent zeolite to long-term stabilization (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Shibaura Institute of Technology*

JAEA-Review 2022-008, 116 Pages, 2022/06

JAEA-Review-2022-008.pdf:5.36MB

The Collaborative Laboratories for Advanced Decommissioning Science (CLADS), Japan Atomic Energy Agency (JAEA), had been conducting the Nuclear Energy Science & Technology and Human Resource Development Project (hereafter referred to "the Project") in FY2020. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. (TEPCO). For this purpose, intelligence was collected from all over the world, and basic research and human resource development were promoted by closely integrating/collaborating knowledge and experiences in various fields beyond the barrier of conventional organizations and research fields. The sponsor of the Project was moved from the Ministry of Education, Culture, Sports, Science and Technology to JAEA since the newly adopted proposals in FY2018. On this occasion, JAEA constructed a new research system where JAEA-academia collaboration is reinforced and medium-to-long term research/development and human resource development contributing to the decommissioning are stably and consecutively implemented. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of the sintering solidification method for spent zeolite to long-term stabilization" conducted from FY2018 to FY2021 (this contract was extended to FY2021). Since the final year of this proposal was FY2021, the results for four fiscal years were summarized. The present study aims to develop a new sintering solidification method in which glass is added as a binder to spent zeolite which is adsorbed radionuclides such as Cs and the nuclides are immobilized by sintering them. In this project, the optimum conditions for sintering solidification and the basic performance of the sintered solidified body will be evaluated by cold tests, and they will be demonstrated by hot tests. In FY2020, the cold tests

Measurements of thermal conductivity for near stoichiometric (UPuAm)O (z = 0.05, 0.10, and 0.15)

Yokoyama, Keisuke; Watanabe, Masashi; Tokoro, Daishiro*; Sugimoto, Masatoshi*; Morimoto, Kyoichi; Kato, Masato; Hino, Tetsushi*

Nuclear Materials and Energy (Internet), 31, p.101156_1 - 101156_7, 2022/06

https://doi.org/10.1016/j.nme.2022.101156

In current nuclear fuel cycle systems, to reduce the amount of high-level radioactive waste, minor actinides (MAs) bearing MOX fuel is one option for burning MAs using fast reactor. However, the effects of Am content in fuel on thermal conductivity are unclear because there are no experimental data on thermal conductivity of high Am bearing MOX fuel. In this study, The thermal conductivities of near stoichiometric (UPuAm)O solid solutions(z = 0.05, 0.10, and 0.15) have been measured between room temperature (RT) and 1473 K. The thermal conductivities decreased with increasing Am content and satisfied the classical phonon transport model ((A+BT)) up to about 1473 K. A values increased linearly with increasing Am content because the change in ionic radius affects the conduction of the phonon due to the solid solution in U and Am. B values were independent of Am content.

Simulation of the self-propagating hydrogen-air premixed flame in a closed-vessel by an open-source CFD code

Thwe, T. A.; Terada, Atsuhiko; Hino, Ryutaro; Nagaishi, Ryuji; Kadowaki, Satoshi

Journal of Nuclear Science and Technology, 59(5), p.573 - 579, 2022/05

https://doi.org/10.1080/00223131.2021.1990153

The simulations of the combustion of self-propagating hydrogen-air premixed flame are performed by an open-source CFD code. The flame propagation behavior, flame radius, temperature and pressure are analyzed by varying the initial laminar flame speed and grid size. When the initial laminar speed increases, the thermal expansion effects become strong which leads the increase of flame radius along with the increase of flame surface area, flame temperature and pressure. A new laminar flame speed model derived previously from the results of experiment is also introduced to the code and the obtained flame radii are compared with those from the experiments. The formation of cellular flame fronts is captured by simulation and the cell separation on the flame surface vividly appears when the gird resolution becomes sufficiently higher. The propagation behavior of cellular flame front and the flame radius obtained from the simulations have the reasonable agreement with the previous experiments.

Development of an continuous air monitor for the measurement of highly radioactive alpha-emitting particulates (-aerosols) under high humidity environment

Tsubota, Yoichi; Honda, Fumiya; Tokonami, Shinji*; Tamakuma, Yuki*; Nakagawa, Takahiro; Ikeda, Atsushi

Nuclear Instruments and Methods in Physics Research A, 1030, p.166475_1 - 166475_7, 2022/05

https://doi.org/10.1016/j.nima.2022.166475

In the long-lasting decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), the dismantling of nuclear fuel debris (NFD) remaining in the damaged reactors is an unavoidable but significant issue with many technical difficulties. The dismantling is presumed to involve mechanical cutting, generating significant concentrations of particulates containing -radionuclides (-aerosols) that pose significant health risk upon inhalation. In order to minimize the radiation exposure of workers with -aerosols during the dismantling/decommissioning process at 1F, it is essential to monitor the concentration of -aerosols at the point of initial generation, i.e. inside the primary containment vessels (PCV) of the damaged reactors. Toward this end, an monitoring system for -aerosols ( alpha air monitor: IAAM) was developed and its technical performance was investigated under the conditions expected for the actual environments at 1F. IAAM was confirmed to fulfill four technical requirements: (1) steady operation under high humidity, (2) operation without using filters, (3) capability of measuring a high counting rate of -radiation, and (4) selective measurement of -radiation even under high radiation background with /-rays. IAAM is capable of selectively measuring -aerosols with a concentration of 3.3 10 Bq/cm or higher without saturation under a high humid environment (100%-relative humidity) and under high background with /-radiation (up to 100 mSv/h of -radiation). These results demonstrate promising potential of IAAM to be utilized as a reliable monitoring system for -aerosols during the dismantling of NFD, as well as the whole long-lasting decommissioning of 1F.

R&D on Accelerator Driven Nuclear Transmutation System (ADS) at J-PARC, 4; Proton beam technology and neutronics

Meigo, Shinichiro; Nakano, Keita; Iwamoto, Hiroki

Purazuma, Kaku Yugo Gakkai-Shi, 98(5), p.216 - 221, 2022/05

For the realization of accelerator-driven transmutation systems (ADS) and the construction of the ADS target test facility (TEF-T) at J-PARC, it is necessary to study the proton beam handling technology and neutronics for protons in the GeV energy region. Accordingly, the Nuclear Transmutation Division of J-PARC has studied these issues with using J-PARC's accelerator facilities, and so on. This paper introduces these topics.

Marking actinides for separation: Resonance-enhanced multiphoton charge transfer in actinide complexes

Matsuda, Shohei; Yokoyama, Keiichi; Yaita, Tsuyoshi; Kobayashi, Toru; Kaneta, Yui; Simonnet, M.; Sekiguchi, Tetsuhiro; Honda, Mitsunori; Shimojo, Kojiro; Doi, Reisuke; et al.

Science Advances (Internet), 8(20), p.eabn1991_1 - eabn1991_11, 2022/05

https://doi.org/10.1126/sciadv.abn1991

no abstracts in English

Basic study on seismic response of soil-structure interaction system using equivalent linear three-dimensional FEM analysis of reactor building

Ichihara, Yoshitaka*; Nakamura, Naohiro*; Nabeshima, Kunihiko*; Choi, B.; Nishida, Akemi

Kozo Kogaku Rombunshu, B, 68B, p.271 - 283, 2022/04

https://doi.org/10.3130/aijjse.68B.0_271

This paper aims to evaluate the applicability of the equivalent linear analysis method for reinforced concrete, which uses frequency-independent hysteretic damping, to the seismic design of reactor building of the nuclear power plant. To achieve this, we performed three-dimensional FEM analyses of the soil-structure interaction system, focusing on the nonlinear and equivalent linear seismic behavior of a reactor building under an ideal soil condition. From these results, the method of equivalent analysis showed generally good correspondence with the method of the nonlinear analysis, confirming the effectiveness. Moreover, the method tended to lower the structural stiffness compared to the nonlinear analysis model. Therefore, in the evaluation of the maximum shear strain, we consider that the results were more likely to be higher than the results of nonlinear analysis.

Breakdown of linear spin-wave theory and existence of spinon bound states in the frustrated kagome-lattice antiferromagnet

Mattan, K.*; Ono, Toshio*; Kawamura, Seiko; Nakajima, Kenji; Nambu, Yusuke*; Sato, Taku*

Physical Review B, 105(13), p.134403_1 - 134403_8, 2022/04

https://doi.org/10.1103/PhysRevB.105.134403

Spin dynamics of the spin-1/2 kagome-lattice antiferromagnet CsCuSnF was studied using high-resolution, time-of-flight inelastic neutron scattering. The flat mode, a characteristic of the frustrated kagome antiferromagnet, and the low-energy dispersive mode, which is dominated by magnons, can be well described by the linear spin-wave theory. However, the theory fails to describe three weakly dispersive modes between 9 and 14 meV. These modes could be attributed to two-spinon bound states, which decay into free spinons away from the zone center and at a high temperature, giving rise to continuum scattering.