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JAEA Reports

Research on factor analysis and technical process for achieving denuclearization; Denuclearization of Former Soviet Union (Belarus, Kazakhstan and Ukraine)

Tazaki, Makiko; Kimura, Takashi; Shimizu, Ryo; Nakatani, Takayoshi; Suda, Kazunori

JAEA-Review 2023-042, 121 Pages, 2024/03

JAEA-Review-2023-042.pdf:3.01MB

As part of the "Research on Factor Analysis and Technical Processes for Achieving Denuclearization", we investigated denuclearization cases in three former Soviet Union countries, namely Belarus, Kazakhstan, and Ukraine, and analyzed the cases by eight denuclearization factors. We then considered the characteristics and lessons learned from such denuclearization. The denuclearization processes of the three countries differed from country to country, and Ukraine's denuclearization process in particular went through many twists and turns. However, the common factor was that all nuclear-weapon states provided security assurances to the three countries and as a result, they transferred strategic nuclear weapons to Russia and joined the Nuclear Non-proliferation Treaty (NPT) as non-nuclear weapon states. Such decision was partly made possible by the economic and physical assistance provided by the United States and Russia for denuclearization. Furthermore, one of the characteristics of the denuclearization of the three countries is the US's skillful denuclearization strategy toward the three countries. The United States supported the claims that the three countries, like Russia, were parties to the First Strategic Arms Reduction Treaty (START-I), and ultimately allowed them to transfer strategic nuclear warheads to Russia within the framework of START-I and the subsequently achieved the disposal of the warheads in Russia. Furthermore, as a lesson from the denuclearization of the three countries, providing security assurance to denuclearized countries is a strong incentive for denuclearization. However, considering Russia's annexation of Crimea in 2014 and military invasion of Ukraine in February 2022, countries which are required denuclearization will seek stronger security guarantees from nuclear-weapon states. Another lesson is that it is necessary to have a strong presidential initiative the countries concerned.

Journal Articles

Assessment of hydrogen embrittlement behavior in Al-Zn-Mg alloy through multi-modal 3D image-based simulation

Fujihara, Hiro*; Toda, Hiroyuki*; Ebihara, Kenichi; Kobayashi, Masakazu*; Mayama, Tsuyoshi*; Hirayama, Kyosuke*; Shimizu, Kazuyuki*; Takeuchi, Akihisa*; Uesugi, Masayuki*

International Journal of Plasticity, 174, p.103897_1 - 103897_22, 2024/03

 Times Cited Count:0

Hydrogen(H) embrittlement in high-strength aluminum(Al) alloys is a crucial problem. H accumulation at the interface of precipitates in Al alloy is considered to cause embrittlement. However, there is no quantitative knowledge regarding the interaction between H distribution and stress field near cracks. In this study, using a multi-modal three-dimensional image-based simulation combining the crystal plasticity finite element method and H diffusion analysis, we tried to capture the stress distribution near the crack, its influence on the H distribution, and the probability of crack initiation in the experimental condition. As a result, it was found that grain boundary cracks transition to quasi-cleavage cracks in the region where the cohesive energy of the semi-coherent interface of MgZn$$_2$$ precipitates decreases due to H accumulation near the tip. We believe the present simulation method successfully bridges nanoscale delamination and macroscale brittle fracture.

Journal Articles

Denuclearization of Ukraine

Tazaki, Makiko; Kimura, Takashi; Shimizu, Ryo; Nakatani, Takayoshi

Dai-44-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 4 Pages, 2023/11

no abstracts in English

Journal Articles

Research on technical process for achieving denuclearization, 2; Disposal and verification of weapon grade plutonium

Shimizu, Ryo; Nakatani, Takayoshi; Tazaki, Makiko; Kimura, Takashi; Hori, Masato

Dai-44-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 4 Pages, 2023/11

no abstracts in English

Journal Articles

IAEA support for nuclear facilities in Ukraine during Russia's invasion

Kobayashi, Naoki

Dai-44-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 5 Pages, 2023/11

no abstracts in English

Journal Articles

Multi-modal 3D image-based simulation of hydrogen embrittlement crack initiation in Al-Zn-Mg alloy

Higa, Ryota*; Fujihara, Hiro*; Toda, Hiroyuki*; Kobayashi, Masakazu*; Ebihara, Kenichi; Takeuchi, Akihisa*

Keikinzoku, 73(11), p.530 - 536, 2023/11

In Al-Zn-Mg alloys, suppression of hydrogen embrittlement is necessary to improve their strength. In this study, the distribution of stress, strain, and hydrogen concentration in the actual fracture region was investigated using the crystal plasticity finite element method and hydrogen diffusion analysis based on a model derived from three-dimensional polycrystalline microstructural data obtained by X-ray CT. In addition, the distributions of stress, strain, and hydrogen concentration were compared with the actual crack initiation behavior by combining in-situ observation of tensile tests using X-ray CT and simulation. The results show that stress loading perpendicular to the grain boundary due to crystal plasticity dominates grain boundary crack initiation. It was also found that internal hydrogen accumulation due to crystal plasticity has little effect on crack initiation.

Journal Articles

7.2 Source term

Terada, Hiroaki

Ten Hasseigen Karano Mesosukeru Kakusan Shumireshon; Fukushima Daiichi Genshiryoku Hatsudensho Jiko O Fumaete (Kisho Kenkyu Noto Dai-248-Go), p.115 - 121, 2023/09

no abstracts in English

Journal Articles

Prediction system for radioactive impacts in nuclear emergency (SPEEDI, WSPEEDI)

Nagai, Haruyasu; Chino, Masamichi*

Ten Hasseigen Karano Mesosukeru Kakusan Shumireshon; Fukushima Daiichi Genshiryoku Hatsudensho Jiko O Fumaete (Kisho Kenkyu Noto Dai-248-Go), p.1 - 58, 2023/09

no abstracts in English

Journal Articles

Nuclear disaster prevention based on lessons learned from the Fukushima Daiichi Nuclear Power Station accident

Shimada, Kazumasa; Nagai, Haruyasu; Hashimoto, Makoto; Iimoto, Takeshi*

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 65(5), P. 290, 2023/05

This article is part of the special feature article "What should be done from now on after the 1F accident and what should be conveyed to the next generation after the 1F accident?" of the Atomic Energy Society of Japan, which summarizes the discussions and future proposals on nuclear disaster prevention in which the members of the Health Physics and Environment Science Subcommittee have been involved. In view of the recommendations of the Accident Investigation Committee of the Atomic Energy Society of Japan and the Meteorological Society of Japan, the behavior of radioactive plumes and the prediction of residents' evacuation behavior should be studied to support decision-making on evacuation and other protective measures for residents in and outside the UPZ. Furthermore, decision-making on protective measures and practical risk communication to residents based on radiation health risks to residents and ethical aspects are newly proposed.

Journal Articles

Denuclearization study on possible future options for dismantlement and verification of Uranium Enrichment Facility

Hori, Masato; Tazaki, Makiko; Shimizu, Ryo; Kimura, Takashi; Nakatani, Takayoshi

Proceedings of INMM & ESARDA Joint Annual Meeting 2023 (Internet), 8 Pages, 2023/05

To improve preparedness of future denuclearization, series of study to achieve effective and efficient denuclearization have been performed in JAEA. As part of this study, this paper focus on dismantlement and verification of potential uranium enrichment facility and potential nuclear material in the uranium enrichment facility, considering (a) peaceful use operation, (b) freeze, (c) disablement, (d) dismantlement, (e) removal from the state as potential options.

Journal Articles

Oxygen diffusion in the fluorite-type oxides CeO$$_{2}$$, ThO$$_{2}$$, UO$$_{2}$$, PuO$$_{2}$$, and (U, Pu)O$$_{2}$$

Kato, Masato; Watanabe, Masashi; Hirooka, Shun; Vauchy, R.

Frontiers in Nuclear Engineering (Internet), 1, p.1081473_1 - 1081473_10, 2023/01

Journal Articles

Statistical analysis of simulated oceanic dispersion of dissolved radionuclide hypothetically released from the Fukushima Dai-ichi Nuclear Power Plant using long-term oceanographic reanalysis data

Ikenoue, Tsubasa; Kawamura, Hideyuki; Kamidaira, Yuki

Journal of Nuclear Science and Technology, 60(1), p.61 - 71, 2023/01

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

We conducted numerical simulations on the oceanic dispersion of dissolved radionuclide hypothetically released from the Fukushima Dai-ichi Nuclear Power Plant using long-term oceanographic reanalysis data. We evaluated the characteristics and trends of dissolved radionuclide behavior in the ocean using statistical analysis based on the simulation results. The surface meridional current at the release point in the Fukushima coastal ocean and the Kuroshio Extension significantly affected the north-south transport of the surface radionuclide in the Fukushima coastal ocean and the eastward transport of the offshore surface radionuclide, respectively. Because the surface kinetic energy in the coastal to the offshore area was larger, the range of the dispersed surface radionuclide tended to be larger. In summer (July-September), the increased frequency radionuclide entrainment by the Kuroshio Extension because of the surface southward radionuclide transport in the Fukushima coastal ocean and the large surface kinetic energy caused a large dispersed surface radionuclide. In winter (January-March), the decreased frequency radionuclide entrainment by the Kuroshio Extension because of the surface northward radionuclide transport in the Fukushima coastal ocean and the small surface kinetic energy caused a small dispersed surface radionuclide.

Journal Articles

Research on technical process for achieving denuclearization, 4; Dismantlement and verification of reprocessing facilities

Shimizu, Ryo; Nakatani, Takayoshi; Tazaki, Makiko; Kimura, Takashi; Hori, Masato

Dai-43-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 3 Pages, 2022/11

no abstracts in English

Journal Articles

Estimation of children's thyroid equivalent doses in 16 municipalities after the Fukushima Daiichi Nuclear Power Station accident

Suzuki, Gen*; Ishikawa, Tetsuo*; Oba, Takashi*; Hasegawa, Arifumi*; Nagai, Haruyasu; Miyatake, Hirokazu*; Yoshizawa, Nobuaki*

Journal of Radiation Research (Internet), 63(6), p.796 - 804, 2022/11

 Times Cited Count:2 Percentile:27.14(Biology)

To elucidate the association between radiation dose and thyroid cancer after the 2011 Fukushima Daiichi Nuclear Power Station (FDNPS) accident, it is essential to estimate individual thyroid equivalent doses (TEDs) to children. In a previous study, we reported a methodology for reconstructing TEDs from inhalation based on individual behavioural survey sheets combined with a spatiotemporal radionuclides database constructed by an atmospheric transport, diffusion, and deposition model (ATDM). In the present study, we further refined our methodology and estimated the combined TEDs from inhalation and ingestion among children in 16 municipalities around the nuclear power station utilizing 3,256 individual whereabouts questionnaire survey sheets. Distributions of estimated TEDs were similar to estimates based on direct thyroid measurements in 1080 children in Iwaki City, Kawamata Town, Iitate Village, and Minamisoma City. Mean TEDs in 1-year-old children ranged from 1.3 mSv in Date City to 14.9 mSv in Odaka Ward in Minamisoma City, and the 95th percentiles varied from 2.3 mSv in Date City to 28.8 mSv in Namie Town. In the future, this methodology can be useful for a case-control study of thyroid cancer after the FDNPS accident.

Journal Articles

Development of evaluation method for core deformation reactivity in sodium-cooled fast reactor; Verification of core deformation reactivity evaluation based on first-order perturbation theory

Doda, Norihiro; Kato, Shinya; Iida, Masaki*; Yokoyama, Kenji; Tanaka, Masaaki

Proceedings of 12th Japan-Korea Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS12) (Internet), 8 Pages, 2022/10

In the conventional core design in sodium-cooled fast reactors (SFRs), negative reactivity feedback due to core deformation was neglected because of large uncertainty in analytical evaluation. To optimize core design, it is necessary to develop an analytical evaluation method and eliminate excessive conservativeness. An evaluation method for core deformation reactivity has been developed by coupling analysis of neutronics, thermal-hydraulics, and structural mechanics. For the verification study of the neutronics calculation method, the reactivity was calculated for the deformed core geometry in which the fuel assembly (FA) moved horizontally in the radial direction for each row from the core center. Compared to reference values derived from Monte Carlo calculations, the calculated reactivity due to FA displacement agreed well in the core region and was overestimated in the reflector region. The modification challenges in development of the core deformation model were identified.

Journal Articles

Hydrogen absorption and diffusion behaviors in cube-shaped palladium nanoparticles revealed by ambient-pressure X-ray photoelectron spectroscopy

Tang, J.*; Seo, O.*; Rivera Rocabado, D. S.*; Koitaya, Takanori*; Yamamoto, Susumu*; Namba, Yusuke*; Song, C.*; Kim, J.*; Yoshigoe, Akitaka; Koyama, Michihisa*; et al.

Applied Surface Science, 587, p.152797_1 - 152797_8, 2022/06

 Times Cited Count:7 Percentile:77.62(Chemistry, Physical)

The hydrogen absorption and diffusion mechanisms on cube-shaped Pd nanoparticles (NPs) which are important hydrogen-storage materials were studied using X-ray photoelectron spectroscopy and DFT calculations. In the surface region, hydrogen absorption showed almost similar behavior regardless of the NPs size. It was found that the octahedral sites are more favorable than the tetrahedral sites for hydrogen occupation. We also clarified that the hydrogen atoms absorbing on the smaller-sized Pd NPs diffuse to the subsurface more actively because of the weakened Pd-H bond by the surface disordering, which plays an important role in hydrogen adsorption at a low H$$_{2}$$ pressure.

JAEA Reports

Research on factor analysis and technical process for achieving denuclearization; Case study and factor analysis of denuclearization

Tazaki, Makiko; Shimizu, Ryo; Kimura, Takashi; Tamai, Hiroshi; Nakatani, Takayoshi; Suda, Kazunori

JAEA-Review 2021-076, 108 Pages, 2022/03

JAEA-Review-2021-076.pdf:3.89MB

In order to find ways to lead the denuclearization successfully, effectively, and efficiently in the future, "Research on factor analysis and technical process for achieving denuclearization" has been conducted since 2018. This report covers the first half of the research, namely "Factor analysis for denuclearization", summarizing the results of the case study and factor analysis of denuclearization. First, South Africa, Iraq, Libya, Ukraine, Kazakhstan, Belarus, North Korea, Iran and Syria were selected as the initial research target countries, and the history of nuclear development as well as characteristics of denuclearization in each country were investigated and analyzed. Next, in order to consider the measures for the international community to lead the denuclearization of the target countries, eight main denuclearization factors ((1) Motivation for nuclear development, (2) Internal and external situation at the time of the denuclearization, (3) Progress of nuclear development, (4) Effects of sanctions, (5) International framework for denuclearization, (6) Incentives for denuclearization, (7) Denuclearization method, (8) Verification method/verifier) were found out. Finally, the contents of each denuclearization factor from (1) to (8)) in above target countries except Syria were analyzed, together with whether each factor was effective for denuclearization or not. In addition, in order to lead denuclearization effectively and efficiently, what should be done in relation to the eight factors were considered. These results are expected to serve as a basis for research on the technological process of denuclearization, and to help considering the way to accomplish denuclearization.

Journal Articles

Defect equilibria and thermophysical properties of CeO$$_{2-x}$$ based on experimental data and density functional theory calculation result

Watanabe, Masashi; Nakamura, Hiroki; Suzuki, Kiichi; Machida, Masahiko; Kato, Masato

Journal of the American Ceramic Society, 105(3), p.2248 - 2257, 2022/03

 Times Cited Count:1 Percentile:6.98(Materials Science, Ceramics)

Properties of CeO$$_{2}$$ were evaluated by DFT simulation to determine band gap, Frenkel defect formation energy and defect migration energy. Band gap and Frenkel defect formation energy were used to analyze defect equilibria. Oxygen partial pressure dependence of defect equilibria was evaluated based on oxygen potential experimental data and DFT calculation, and a Brouwer diagram was derived. The defect formation energies, including Frenkel defect, electron-hole pair and so on, were determined and used to evaluate the properties, including oxygen diffusion coefficients, electrical conduction, heat capacity and thermal conductivity. Mechanisms of various properties were discussed for a deeper understanding based on defect chemistry, and the relationship among properties were systematically described.

Journal Articles

Radiation-enhanced diffusion of copper in iron studied by three-dimensional atom probe

Toyama, Takeshi*; Suzudo, Tomoaki; Nagai, Yasuyoshi*; 9 of others*

Journal of Nuclear Materials, 556, p.153176_1 - 153176_7, 2021/12

 Times Cited Count:2 Percentile:31.78(Materials Science, Multidisciplinary)

We performed a high-precision investigation of radiation-enhanced diffusion (RED) using electron irradiation and three-dimensional atom probe (3D-AP). Cu-Fe diffusion pairs were created using high-purity Fe and Cu as base materials, and irradiated by 2 MeV electron. Cu diffusion into the Fe matrix was observed at the atomic level using 3D-AP, and the diffusion coefficient was obtained directly using Fick's law. RED was clearly observed, and the ratio of diffusion under irradiation to thermal diffusion was enhanced at low temperature. RED was quantitatively evaluated using the reaction kinetics model, and the model which consider only vacancies gave a good agreement. This gave experimental clarification that RED was dominated by irradiation-induced vacancies. In addition, the direct experimental results on the effect of irradiation on the solubility limits of Cu in Fe was obtained; solubility limits under irradiation were found to be lower than those under thermal aging.

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