Selective resonance ionization of odd calcium isotopes using linearly polarized lasers

Iwata, Yoshihiro; Miyabe, Masabumi; Wells, S. R.*; Yamamoto, Yuta*; Hasegawa, Shuichi*

Proceedings of International Topical Workshop on Fukushima-Daiichi Decommissioning Research 2024 (FDR2024) (Internet), 4 Pages, 2024/10

In this study, triple and double resonance ionization schemes of atomic Ca were developed, aiming for the separation of odd isotopes by (i) laser polarization-dependent selection rules, and (ii) large isotope shifts of odd Ca isotopes in the Rydberg levels. Separation of odd isotopes was confirmed under the orthogonal condition. Suppression of non-resonant ionization of Ca by the electric field in the ionization region could further improve the optical isotope selectivity of Ca.

First demonstration of a single-end readout position-sensitive optical fiber radiation sensor inside the Fukushima Daiichi Nuclear Power Station based on wavelength-resolving analysis

Terasaka, Yuta; Sato, Yuki; Uritani, Akira*

Nuclear Instruments and Methods in Physics Research A, 1062, p.169227_1 - 169227_6, 2024/05

https://doi.org/10.1016/j.nima.2024.169227

Resonance ionization spectroscopy of high-lying 4sns and 4snd Rydberg levels of odd calcium isotopes

Iwata, Yoshihiro; Miyabe, Masabumi; Akaoka, Katsuaki; Wakaida, Ikuo; Hasegawa, Shuichi*

Journal of the Optical Society of America B, 41(1), p.119 - 126, 2024/01

https://doi.org/10.1364/JOSAB.507539

Calcium Rydberg levels are of significant interest for efficient and isotope-selective resonance ionization of trace radionuclides such as calcium-41 (Ca). In this study, we report novel measurement data on the energy level shifts of calcium-43 (Ca) for 4sns S and 4s(n-1)d D (n=40, 45, 50, 55, 60) Rydberg levels due to hyperfine-induced singlet-triplet mixing specific to isotopes with an odd mass number.

Measurement methods for the radioactive source distribution inside reactor buildings using a one-dimensional optical fiber radiation sensor (Contract research); FY2021 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Nagoya University*

JAEA-Review 2022-033, 80 Pages, 2022/12

JAEA-Review-2022-033.pdf:4.08MB

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 FY2021. The Project aims to contribute to solving problems in the nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station (1F), 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 FY2019, this report summarizes the research results of the "Measurement methods for the radioactive source distribution inside reactor buildings using a one-dimensional optical fiber radiation sensor" conducted from FY2019 to FY2021. Since the final year of this proposal was FY2021, the results for three fiscal years were summarized. The present study aims to develop an optical fiber type radiation sensor that can measure the radiation distribution one-dimensionally along the fiber under a high radiation field for the decommissioning of 1F. Based on the conventional time-of-flight method, we found several promising sensor candidates for the radiation distribution measurement under high dose rate and many scattered gamma-rays.

Measurement of nuclide production cross-sections in high-energy proton-induced spallation reactions at J-PARC

Nakano, Keita; Matsuda, Hiroki*; Meigo, Shinichiro; Iwamoto, Hiroki; Takeshita, Hayato*; Maekawa, Fujio

JAEA-Research 2021-014, 25 Pages, 2022/03

JAEA-Research-2021-014.pdf:2.1MB

For the development of accelerator-driven transmutation system (ADS), measurement of nuclide production cross-sections in proton-induced reactions on Be, C, Al, Sc, and V have been performed. The measured data are compared with the calculations by the latest nuclear reaction models and with the nuclear data library to investigate the reproducibilities.

Development of high-resolution imaging camera for alpha dust (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*

JAEA-Review 2021-044, 58 Pages, 2022/01

JAEA-Review-2021-044.pdf:3.53MB

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 high-resolution imaging camera for alpha dust" conducted in FY2020. The present study aims to develop a novel alpha-ray camera consisting of imaging and an energy spectrometer to find the alpha dust to reduce the risk of health damage in Decommissioning. We have developed the camera in FY2020, and the measurement test for the energy spectra. Moreover, the imaging test has been operated. In addition, we have also developed a high-dose-rate monitor system using novel scintillators with red/infra-red emission.

Evaluation of the minimum critical amount for heterogeneous lattice systems composed of fuel rods utilized in low-power water-moderated research and test reactors by using continuous-energy Monte Carlo code MVP with JENDL-4.0

Yanagisawa, Hiroshi

JAEA-Technology 2021-023, 190 Pages, 2021/11

JAEA-Technology-2021-023.pdf:5.25MB

Computational analyses on nuclear criticality characteristics were carried out for heterogeneous lattice systems composed of water moderator and fuel rods utilized in low-power research and test reactors, in which the depletion of fuel due to burnup is relatively small, by using the continuous-energy Monte Carlo code MVP Version 2 with the evaluated nuclear data library JENDL-4.0. In the analyses, the minimum critical number of fuel rods was evaluated using calculated neutron multiplication factors for the heterogeneous systems of the uranium dioxide fuel rod in the Static Experiments Critical Facility (STACY) and the Tank-type Critical Assembly (TCA), and the uranium-zirconium hydride fuel rod in the Nuclear Safety Research Reactor (NSRR). In addition, six sorts of the ratio of reaction rates, which are components of neutron multiplication factors, were calculated in the analyses to explain the variation of neutron multiplication factors with the ratio of water moderator to fuel volume in a unit fuel rod cell. Those results of analyses are considered to be useful for the confirmation of reasonableness and validity of criticality safety measures as data showing criticality characteristics for water-moderated heterogeneous lattice systems composed of the existing fuel rods in research and test reactors, of which criticality data are not sufficiently provided by the Criticality Safety Handbook.

Feasibility study on tritium recoil barrier for neutron reflectors of research and test reactors

Kenzhina, I.*; Ishitsuka, Etsuo; Ho, H. Q.; Sakamoto, Naoki*; Okumura, Keisuke; Takemoto, Noriyuki; Chikhray, Y.*

Fusion Engineering and Design, 164, p.112181_1 - 112181_5, 2021/03

https://doi.org/10.1016/j.fusengdes.2020.112181

Tritium release into the primary coolant during operation of the JMTR (Japan Materials Testing Reactor) and the JRR-3M (Japan Research Reactor-3M) had been studied. It is found that the recoil release by Li(n,)H reaction, which comes from a chain reaction of beryllium neutron reflectors, is dominant. To prevent tritium recoil release, the surface area of beryllium neutron reflectors needs to be minimum in the core design and/or be shielded with other material. In this paper, as the feasibility study of the tritium recoil barrier for the beryllium neutron reflectors, various materials such as Al, Ti, V, Ni, and Zr were evaluated from the viewpoint of the thickness of barriers, activities after long-term operations, and effects on the reactivities. From the results of evaluations, Al would be a suitable candidate as the tritium recoil barrier for the beryllium neutron reflectors.

Evaluation of tritium release into primary coolant for research and testing reactors

Kenzhina, I.*; Ishitsuka, Etsuo; Okumura, Keisuke; Ho, H. Q.; Takemoto, Noriyuki; Chikhray, Y.*

Journal of Nuclear Science and Technology, 58(1), p.1 - 8, 2021/01

https://doi.org/10.1080/00223131.2020.1791760

The sources and mechanisms for the tritium release into the primary coolant in the JMTR and the JRR-3M containing beryllium reflectors are evaluated. It is found that the recoil release from chain reaction of Be is dominant and its calculation results agree well with trends derived from the measured variation of tritium concentration in the primary coolant. It also indicates that the simple calculation method used in this study for the tritium recoil release from the beryllium reflectors can be utilized for an estimation of the tritium release into the primary coolant for a research and testing reactors containing beryllium reflectors.

Improvement of adsorption performances of Sr adsorption fiber and investigation for realizing simple Sr analysis

Horita, Takuma; Asai, Shiho*; Konda, Miki; Matsueda, Makoto; Hanzawa, Yukiko; Kitatsuji, Yoshihiro

Bunseki Kagaku, 69(10/11), p.619 - 626, 2020/10

https://doi.org/10.2116/bunsekikagaku.69.619

We have developed a Sr adsorption fiber for rapid analysis of Sr. The prepared Sr adsorption fiber has a Sr-extraction layer that densely retains a Sr-selective extractant, an 18-crown-6 ether derivative, on the fiber surface. Hydrophobic group-containing polymer chains embedded onto the surface of the fiber allow to form a hydrophobic phase, incorporating Sr-selective extractants. This unique surface structure provides high adsorption capacity, leading to rapid and highly efficient adsorption of Sr. The adsorption capacity of the Sr adsorption fiber was 3 times higher than commercially available 18-crown-6 ether derivative-impregnated resin (Sr Resin). The equilibrium adsorption capacity of the Sr adsorption fiber was comparable to the Sr Resin. The retained Sr was finally determined by a GM counter. The total analysis time including the Sr adsorption and measurement was about 1 hour.