Radio-tellurium released into the environment during the complete oxidation of fuel cladding, containment venting and reactor building failure of the Fukushima accident

Hidaka, Akihide; Kawashima, Shigeto*; Kajino, Mizuo*

Journal of Nuclear Science and Technology, 60(7), p.743 - 758, 2023/07

https://doi.org/10.1080/00223131.2022.2142311

An accurate estimation of radionuclides released during the Fukushima accident is essential. Therefore, authors investigated Te release using the Unit emission-regression estimation method, in which the deposition distribution is weighted based on the hourly deposition obtained from mesoscale meteorological model calculations assuming Unit emissions. The previous study focused on confirming the applicability of this method. Subsequent examination revealed that if any part of the time when a release have occurred is missing from the estimated release period, the entire source term calculation will be distorted. Therefore, this study performed the recalculation by extending the estimation period to cover all major releases. Consequently, unspecified release events were clarified, and their correspondence to in-core events was confirmed. The Te release caused by Zr cladding complete oxidation can explain the regional dependence of the Te/Cs ratio in the soil contamination map.

Double diffusive dissolution model of UO pellet in molten Zr cladding

Ito, Ayumi*; Yamashita, Susumu; Tasaki, Yudai; Kakiuchi, Kazuo; Kobayashi, Yoshinao*

Journal of Nuclear Science and Technology, 60(4), p.450 - 459, 2023/04

https://doi.org/10.1080/00223131.2022.2114956

Measurement of nuclide production cross sections for proton-induced reactions on Ni and Zr at 0.4, 1.3, 2.2, and 3.0 GeV

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

Nuclear Instruments and Methods in Physics Research B, 527, p.17 - 27, 2022/09

https://doi.org/10.1016/j.nimb.2022.07.002

To improve accuracy of nuclear design of accelerator driven nuclear transmutation systems and so on, nuclide production cross sections on Ni and Zr were measured for GeV energy protons. The measured results were compared with PHITS calculations, JENDL/HE-2007 and so on.

Development of technology to simultaneously measure viscosity and surface tension of molten materials in reactor core (Contract research); FY2020 Nuclear Energy Science & Technology and Human Resource Development Project

Collaborative Laboratories for Advanced Decommissioning Science; Osaka University*

JAEA-Review 2021-046, 77 Pages, 2022/01

JAEA-Review-2021-046.pdf:2.92MB

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 technology to simultaneously measure viscosity and surface tension of molten materials in reactor core" conducted from FY2018 to FY2020. Since the final year of this proposal was FY2020, the results for three fiscal years were summarized. Since (U, Zr)O and boride, molten materials in reactor core, exist at extremely high temperature, chemical reactions between the vessel and these molten materials are unavoidable. Therefore, it is difficult to measure the thermophysical property of these materials. In the present study, droplets are produced by heating and melting the samples levitated by a gas levitation method, then the droplets are collided with a substrate.

Development of HCl-free solid phase extraction combined with ICP-MS/MS for rapid assessment of difficult-to-measure radionuclides, 1; Selective measurement of Zr and Mo in concrete rubble

Do, V. K.; Furuse, Takahiro; Murakami, Erina; Aita, Rena; Ota, Yuki; Sato, Soichi

Journal of Radioanalytical and Nuclear Chemistry, 327(1), p.543 - 553, 2021/01

https://doi.org/10.1007/s10967-020-07503-z

A new HCl-free chromatographic separation procedure has been developed for sequential separation of Zr and Mo from concrete matrices. Accordingly, Zr and Mo could be sensitively and selectively measured by ICP-MS/MS using ammonia reaction gas. The recoveries of greater than 90% for Zr and Mo from concretes could be achieved. The measurement condition was optimized for complete suppression of interferences from Nb and peak tailing from abundant isotopes of Zr and Mo in concrete matrices. The removal of interferences was verified by measurement of radio-contamination-free concretes used as a sample matrix blank. Method detection limits of 1.7 mBq g and 0.2 Bq g were achieved for Zr and Mo, respectively, in the concrete matrices. The interference removal factor for Nb (equivalent to the decontamination factor in radiochemical separation) was of the order of 10, and the abundance sensitivity was of the order of 10, indicating that the developed method is reliable for verifying the presence of ultralow concentrations of Zr and Mo. The present method is suitable for the rapid assessment of Zr and Mo for radioactivity inventory of concrete rubble.

Development of technology to simultaneously measure viscosity and surface tension of molten materials in reactor core (Contract research); FY2018 Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development

Collaborative Laboratories for Advanced Decommissioning Science; Osaka University*

JAEA-Review 2019-025, 36 Pages, 2020/01

JAEA-Review-2019-025.pdf:2.57MB

CLADS, JAEA, had been conducting the Center of World Intelligence Project for Nuclear Science/Technology and Human Resource Development (hereafter referred to "the Project") in FY2018. The Project aims to contribute to solving problems in nuclear energy field represented by the decommissioning of the Fukushima Daiichi Nuclear Power Station, Tokyo Electric Power Company Holdings, Inc. 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 Technology to Simultaneously Measure Viscosity and Surface Tension of Molten Materials in Reactor Core". Since (U,Zr)O and boride, molten materials in reactor core, exist at extremely high temperature, chemical reactions between the vessel and these molten materials are unavoidable. Therefore, it is difficult to measure the thermophysical property of these materials. In the present study, droplets are produced by heating and melting the samples levitated by a gas levitation method, then the droplets are collided with a substrate. From the instant behavior of the collision, a new technology to simultaneously derive the viscosity and surface tension will be developed.

Structure change of monoclinic ZrO baddeleyite involving softenings of bulk modulus and atom vibrations

Fukui, Hiroshi*; Fujimoto, Manato*; Akahama, Yuichi*; Sano, Asami; Hattori, Takanori

Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 75(4), p.742 - 749, 2019/08

https://doi.org/10.1107/S2052520619007923

Monoclinic ZrO baddeleyite exhibits anomalous softenings of bulk modulus and atom vibrations with compression. We have investigated the pressure evolution of the structure by neutron powder diffraction combined with ab-initio calculations. The present results showed that the anomalous pressure response of the bulk modulus is related not to the change in the bonding characters but to the deformation of an oxygen sublattice, especially one of layers made of oxygens in the crystallographic * plane. The layer consists of two parallelograms; one is rotating with little distortion and the other is being distorted with increasing pressure. This deformation of this layer makes one of Zr-O distances long, resulting in the softening of some atom vibrational modes.

Oxidation kinetics of Zry-4 fuel cladding in mixed steam-air atmospheres at temperatures of 1273 - 1473 K

Negyesi, M.; Amaya, Masaki

Journal of Nuclear Science and Technology, 54(10), p.1143 - 1155, 2017/10

https://doi.org/10.1080/00223131.2017.1344583

Separation of Zr in the rubble waste generated at the Fukushima Daiichi Nuclear Power Station

Shimada, Asako; Kameo, Yutaka

Journal of Radioanalytical and Nuclear Chemistry, 311(3), p.1613 - 1618, 2017/03

AA2016-0191.pdf:0.23MB

https://doi.org/10.1007/s10967-016-5126-5

Separation method of Zr using trans uranium resin (TRU resin) was developed. Approximately 100% of Zr, Nb, Bi, Th, and U and a part of Mo and Hg were extracted on the TRU resin from 3 M HNO solution and separated from Li, Be, Mg, Al, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr,Ag, Cd, In, Cs, Ba. Approximately 100% of Zr, Nb, and U were striped from the TRU resin with 0.01 M HF and 10% of Mo, 7.1% of Hg, 77% of Bi, and 20% of Th were also included in the stripping solution. In order to measure Zr with inductively coupled plasma mass spectrometry (ICP-MS), Zr has to be separated from Nb and Mo to avoid isobaric interference. Therefore, further purification of Zr using tetra valent actinide resin (TEVA resin) was applied. The developed method was evaluated with the simulated rubble sample solution. Although a part of Zr was eluted during sample loading, most of Zr was extracted on the TRU resin and separated major elements of the rubble sample. Finally, Zr was separated from Nb and Mo with the TEVA resin.

Neutronics assessment of advanced shield materials using metal hydride and borohydride for fusion reactors

Hayashi, Takao; Tobita, Kenji; Nishio, Satoshi; Ikeda, Kazuki*; Nakamori, Yuko*; Orimo, Shinichi*; DEMO Plant Design Team

Fusion Engineering and Design, 81(8-14), p.1285 - 1290, 2006/02

https://doi.org/10.1016/j.fusengdes.2005.09.060

Neutron transport calculations were carried out to evaluate the capability of metal hydrides and borohydrides as an advanced shielding material. Some hydrides indicated considerably higher hydrogen content than polyethylene and solid hydrogen. The hydrogen-rich hydrides show superior neutron shielding capability to the conventional materials. From the temperature dependence of dissociation pressure, ZrH and TiH can be used without releasing hydrogen at the temperature of less than 640 C at 1 atm. ZrH and Mg(BH) can reduce the thickness of the shield by 30% and 20% compared to a combination of steel and water, respectively. Mixing some hydrides with F82H produces considerable effects in -ray shielding. The neutron and -ray shielding capabilities decrease in order of ZrH Mg(BH) and F82H TiH and F82H water and F82H.