Li, W.*; Yamada, Shinya*; Hashimoto, Tadashi; Okumura, Takuma*; Hayakawa, Ryota*; Nitta, Kiyofumi*; Sekizawa, Oki*; Suga, Hiroki*; Uruga, Tomoya*; Ichinohe, Yuto*; et al.
Analytica Chimica Acta, 1240, p.340755_1 - 340755_9, 2023/02
no abstracts in English
Hayashi, Hirokazu; Shibata, Hiroki; Sato, Takumi; Otobe, Haruyoshi
Journal of Radioanalytical and Nuclear Chemistry, 8 Pages, 2023/00
The formation of MPd (M = Gd, Np) by the reaction of MN with Pd at 1323 K in Ar gas flow was observed. Cubic AuCu-type GdPd ( = 0.4081 0.0001 nm) and NpPd ( = 0.4081 0.0001 nm) were identified, respectively. The product obtained from the reaction of NpN with Pd contained additional phases including the hexagonal TiNi-type NpPd. Chlorination of the MPd (M = Gd, Np) samples was accomplished by the solid-state reaction using cadmium chloride at 673 K in a dynamic vacuum. Pd-rich solid solution phase saturated with Cd and an intermetallic compound PdCd were obtained as by-products of MCl formation.
Sato, Takumi; Nagae, Yuji; Kurata, Masaki; Quaini, A.*; Guneau, C.*
CALPHAD; Computer Coupling of Phase Diagrams and Thermochemistry, 79, p.102481_1 - 102481_11, 2022/12
Xu, S.*; Odaira, Takumi*; Sato, Shunsuke*; Xu, X.*; Omori, Toshihiro*; Harjo, S.; Kawasaki, Takuro; Seiner, H.*; Zoubkov, K.*; Murakami, Yasukazu*; et al.
Nature Communications (Internet), 13, p.5307_1 - 5307_8, 2022/09
Yamashita, Takuya; Sato, Takumi; Madokoro, Hiroshi; Nagae, Yuji
Annals of Nuclear Energy, 173, p.109129_1 - 109129_15, 2022/08
Mizumachi, Takumi*; Sato, Minami*; Kaneko, Masashi; Takeyama, Tomoyuki*; Tsushima, Satoru*; Takao, Koichiro*
Inorganic Chemistry, 61(16), p.6175 - 6181, 2022/04
Based on unique 5-fold equatorial coordination of UO, water-compatible pentadentate planar ligands, Hsaldian and its derivatives, were designed as strong and selective capture of UO in seawater. In the simulated seawater condition (0.5 M NaCl + 2.3 mM HCO/CO, pH 8), saldian shows the strongest complexation with UO to form UO(saldian) (log = 28.05 0.07), which is more than 10 order of magnitude greater than amidoxime-based or -inspired ligand systems most commonly employed for U capture from seawater. Good selectivity for UO from other metal ions coexisting in seawater was also demonstrated.
Morishita, Kazuki; Sato, Takumi; Onishi, Takashi; Seki, Takayuki*; Sekine, Shinichi*; Okitsu, Yuichi*
JAEA-Technology 2021-024, 27 Pages, 2021/10
In the case of Plutonium (Pu)-bearing organic materials, organic materials are decomposed by alpha rays emitted mainly from Pu to generate hydrogen gas and other substances. Therefore, to safely store Pu-bearing organic materials for an extended period of time, organic materials must be eliminated. In addition, carbide and nitride fuels must be converted into oxides for safe storage in order to prevent the exothermal reaction of these fuels with oxygen/moisture in air. A survey of the literature on the stabilization treatment of Pu-bearing organic materials confirmed that organic materials can be decomposed and removed by heating at 950 C (1223.15 K) or greater in air. Furthermore, based on the calculated thermodynamic parameters of oxidation reaction of carbide and nitride fuels in air, it was estimated that these fuels would be oxidized in air at 950 C because the equilibrium oxygen partial pressure in the oxidation reaction at 950 C was lower than 2.110 Pa (oxygen partial pressure in air). Therefore, it was decided to stabilize Pu-bearing organic materials by heating at 950 C in air to remove the organic materials and oxidize the carbide and nitride fuels. As a mock-up test to remove the organic materials, thin sheets of epoxy resin were heated in air. The changes in appearance and weight before and after heating in air showed that organic materials can be removed. After the mock-up test, Pu-bearing organic materials were also stabilized by heating in the similar condition.
Kusaka, Ryoji; Kumagai, Yuta; Yomogida, Takumi; Takano, Masahide; Watanabe, Masayuki; Sasaki, Takayuki*; Akiyama, Daisuke*; Sato, Nobuaki*; Kirishima, Akira*
Journal of Nuclear Science and Technology, 58(6), p.629 - 634, 2021/06
Sudo, Ayako; Sato, Takumi; Ogi, Hiroshi; Takano, Masahide
Journal of Nuclear Science and Technology, 58(4), p.473 - 481, 2021/04
Dissolution behavior of Sr and Ba is crucial for evaluating secondary source terms via coolant water from ex-vessel debris accumulated at Fukushima Daiichi Nuclear Power Plant. To understand the mechanism, knowing the distribution of Sr and Ba in the ex-vessel debris is necessary. As a result of reaction tests between simulated corium and concrete materials, two layered structures were observed in the solidified sample, (A) a silicate glass-based ((Si-Al-Ca-Fe-Zr-Cr-U-Sr-Ba)-O) phase-rich layer in the upper surface region and (B) a (U,Zr)O particle-rich layer at the inner region. Measurable concentrations of Sr and Ba were observed in layer (A) (approximately 1.7 times that in the layer (B)). According to thermodynamic analysis, (U,Zr)O is predicted to solidify, in advance, in the concrete-based melt around 2177 C. Then, the residual melt is solidified as a silicate glass, and Sr and Ba are preferentially dissolved into the silicate glass. During the tests, (U,Zr)O particles sank, in advance, in the melt because of its higher density, and the silicate glass phase relocated to the surface layer. On the other hand, silicate glass containing Sr and Ba is predicted to be hardly soluble in water and chemically stable.
Kato, Takemi*; Sugawara, Katsuaki*; Ito, Naohiro*; Yamauchi, Kunihiko*; Sato, Takumi*; Oguchi, Tamio*; Takahashi, Takashi*; Shiomi, Yuki*; Saito, Eiji; Sato, Takafumi*
Physical Review Materials (Internet), 4(8), p.084202_1 - 084202_6, 2020/08
Sudo, Ayako; Meszaros, B.*; Poznyak, I.*; Sato, Takumi; Nagae, Yuji; Kurata, Masaki
Journal of Nuclear Materials, 533, p.152093_1 - 152093_8, 2020/05
Tateno, Haruka; Sato, Takumi; Tsubata, Yasuhiro; Hayashi, Hirokazu
Journal of Nuclear Science and Technology, 57(3), p.224 - 235, 2020/03
Fuel cycle technology for the transmutation of long-lived minor actinides (MAs) using an accelerator-driven system has been developed using the double-strata fuel cycle concept. A mononitride solid solution of MAs and Pu diluted with ZrN is a prime fuel candidate for the accelerator-driven transmutation of MAs. Pyro-reprocessing is suitable for recycling the residual MAs in irradiated nitride fuel with high radiation doses and decay heat. Spent nitride fuel is anodically dissolved, and the actinides are recovered simultaneously into a liquid cadmium cathode via molten salt electrorefining. The process should be designed to achieve the target recovery yield of MAs and the acceptable impurity level of rare earths in the recovered material. We evaluated the material balance during the pyro-reprocessing of spent nitride fuel to gain important insight on the design process. We examined the effects of changing processing conditions on material flow and quantity of waste.
Okudaira, Takuya; Shimizu, Hirohiko*; Kitaguchi, Masaaki*; Hirota, Katsuya*; Haddock, C. C.*; Ito, Ikuya*; Yamamoto, Tomoki*; Endo, Shunsuke*; Ishizaki, Kohei*; Sato, Takumi*; et al.
EPJ Web of Conferences, 219, p.09001_1 - 09001_6, 2019/12
Parity violating effects enhanced by up to 10 times have been observed in several neutron induced compound nuclei. There is a theoretical prediction that time reversal (T) violating effects can also be enhanced in these nuclei implying that T-violation can be searched for by making very sensitive measurements. However, the enhancement factor has not yet been measured in all nuclei. The angular distribution of the (n,) reaction was measured with La by using a germanium detector assembly at J-PARC, and the enhancement factor was obtained. From the result, the measurement time to achieve the most sensitive T-violation search was estimated as 1.4 days, and a 40% polarized La target and a 70% polarized He spin filter whose thickness is 70 atmcm are needed. Therefore high quality He spin filter is developed in JAEA. The measurement result of the (n,) reaction at J-PARC and the development status of the He spin filter will be presented.
Nakanishi, Takahiro; Sato, Seiji; Matsumoto, Takumi*
Radiation Protection Dosimetry, 184(3-4), p.311 - 314, 2019/10
There has been significant concern about an increase of exposure dose in living sphere due to the accumulation of radiocesium discharged from contaminated mountainous forest in Fukushima. In this study, we investigated the history of radiocesium deposition on some floodplains in Fukushima. Radiocesium concentrations of river suspended particles and air dose rates at floodplains were also observed continuously. In many situations, annual sediment accumulation at floodplains was only several kg m and its radiocesium concentration was gradually decreasing in line with that of suspended particle. Simultaneously, air dose rates on floodplains were decreasing with time. In 2015 with heavy flood discharge, several hundred kg m of sediment accumulation and sharply decrease of air dose rate was observed at rivers without reservoir. Conversely, radiocesium accumulation at floodplain was significant reduced due to deposition on upstream reservoir.
Sudo, Ayako; Mizusako, Fumiki*; Hoshino, Kuniyoshi*; Sato, Takumi; Nagae, Yuji; Kurata, Masaki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 18(3), p.111 - 118, 2019/08
Cooling rate of molten core materials during solidification significantly affects the segregation of major constituents of fuel debris. To understand general tendency of the segregation, liquefaction/solidification tests of simulated corium (UO, ZrO, FeO, BC and sim-FP oxides) were performed. Simulated corium was heated up to 2600C under Ar atmosphere and then cooled down with two different cooling processes; furnace cooling (average cooling rate is approximately 744C/min) and slow cooling (cooling rate in 2600C2300C is 5C/min and in 2300C1120C is approximately 788C/min). Element analysis detected three oxide phases with different composition and one metal phase in both solidified samples. Solubility of FeO in these oxide phases was mostly fixed to be 125at% in both samples, which is in reasonable accordance with the value estimated from UO-ZrO-FeO phase diagrams. However, a significant grain-growth of one oxide phase, rich in Zr-oxide, was detected only in the slowly cooled sample. The composition of this particular oxide phase is comparable to the initial average composition. The condensation is considered to be caused by the connection of remaining liquid agglomerates during slow solidification.
Marufuji, Takato; Sato, Takumi; Ito, Hideaki; Suzuki, Hisashi; Fujishima, Tadatsune; Nakano, Tomoyuki
JAEA-Technology 2019-006, 22 Pages, 2019/05
Radioactive contamination incident occurred at Plutonium Fuel Research Facility (PFRF) in Oarai Research and Development Institute, Japan Atomic Energy Agency on June 6, 2017. During inspection work of storage container containing nuclear fuel materials, the PVC bag packaging in the storage container ruptured when a worker opened the lid in the hood, and a part of contents was spattered over the room. The cause of the increase of internal pressure of the storage container was gas generation by alpha radiolysis of the epoxy resin mixed with nuclear fuel materials. Opening inspection of about 70 similar containers stored in PFRF has been planned to confirm the condition of the contents and to stabilize the stored materials containing organic compounds. For safe and reliable open inspection of the storage containers with high internal pressure in the glove box, it is necessary to develop a pressure-resistant chamber in which the storage containers are opened and the contents are inspected under gastight condition. This report summarizes the concerns and countermeasures of the chamber design and the design results of the chamber.
Kimuro, Shingo*; Kirishima, Akira*; Nagao, Seiya*; Saito, Takumi*; Amano, Yuki; Miyakawa, Kazuya; Akiyama, Daisuke*; Sato, Nobuaki*
Journal of Nuclear Science and Technology, 55(5), p.503 - 515, 2018/05
no abstracts in English
Hayashi, Hirokazu; Sato, Takumi; Shibata, Hiroki; Tsubata, Yasuhiro
NEA/NSC/R(2017)3, p.427 - 432, 2017/11
Transmutation of long-lived radioactive nuclides including minor actinides (MA: Np, Am, Cm) has been studied in Japan Atomic Energy Agency (JAEA). Pb-Bi cooled sub-critical accelerator-driven system (ADS) is regarded as one of the powerful tools for transmutation of MA under the double strata fuel cycle concept. Uranium-free MA-Pu nitride fuel was chosen as the first candidate for MA transmutation. Reprocessing of spent ADS fuel and reusing MA recovered from the spent ADS fuels is necessary to improve the transmutation ratio. A pyrochemical process has been proposed as the first candidate for reprocessing of the spent nitride fuel for MA transmutation, because this technique has some advantages over aqueous process, such as the resistance to radiation damage, which is an important issue for the fuels containing large amounts of highly radioactive MA, and feasibility for recovering expensive N-15 in the spent fuels to be reused. This paper overviews the current status of the technology development, including our recent study. Development of the anode suitable for electro-refining of nitride fuels and that of the apparatus for renitridation of the metals recovered in Cd cathode for 100g-Cd scale cold tests are main topics. Evaluation of the batch sizes of each process, which is necessary for estimating the scale of the engineering-apparatus, with considering the decay heat of MA and FP, will also be introduced.
Kirishima, Akira*; Kuno, Atsushi*; Amamiya, Hiroki; Kubota, Takumi*; Kimuro, Shingo*; Amano, Yuki; Miyakawa, Kazuya; Iwatsuki, Teruki; Mizuno, Takashi; Sasaki, Takayuki*; et al.
Chemosphere, 168, p.798 - 806, 2017/02
For better understanding of the migration behavior of minor actinides (MA) in deep groundwater, the interaction of doped rare earth elements (REEs) and components in Horonobe deep groundwater was studied. Appx. 10 ppb of rare earth elements, i.e., Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm and Yb were doped to the sample groundwater collected from a packed sections in borehole drilled from 140 m depth experiment drift of Horonobe underground research laboratory (URL), Hokkaido, Japan. Then, that groundwater was sequentially filtrated by 0.2 micron pore filter, 10 kDa, 3 kDa and 1 kDa of nominal molecular weight limit (NMWL) ultrafilters by keeping inert condition. After that, the filtrate solutions were analyzed by ICP-MS to determine the concentrations of retained REEs at each filtration steps, while the used filters were analyzed by the neutron activation analysis (NAA) and TOF-SIMS element mapping to know the amount and chemical speciation of trapped fraction of the REEs on each filter. A remarkable relation between the retention ratios of REEs in the filtrate solutions and the ionic radius was observed, i.e., smaller rare earth element solves more in liquid phase under the Horonobe groundwater condition. NAA and TOF-SIMS analyses revealed that certain portions of REEs were trapped by 0.2 micron pore filters as rare earth phosphates which corresponded with the predicted predominant species by a chemical equilibrium calculation for the Horonobe groundwater condition, while small portions of colloidal REEs were trapped by 10 kDa and 3 kDa NMWL ultrafilters. The result suggested that phosphate anion plays an important role in the chemical behavior of REEs in saline (seawater based) groundwater, which could be referred for the prediction of migration behavior of trivalent actinide released from the repository of radioactive waste in far future.
Edao, Yuki; Sato, Katsumi; Iwai, Yasunori; Hayashi, Takumi
Journal of Nuclear Science and Technology, 53(11), p.1831 - 1838, 2016/11