Sasaki, Yuji; Morita, Keisuke
Progress in Nuclear Science and Technology (Internet), 5, p.27 - 32, 2018/12
no abstracts in English
Tateiwa, Naoyuki; Pospil, J.*; Haga, Yoshinori; Sakai, Hironori; Matsuda, Tatsuma*; Yamamoto, Etsuji
Progress in Nuclear Science and Technology (Internet), 5, p.104 - 107, 2018/12
Uranium ferromagnetic superconductors UGe, URhGe and UCoGe have attracted much attention from both theoretical and experimental sides since the same 5 electrons underlie carry both the ferromagnetism and superconductivity. Recently, we have analysed 69 uranium, 7 neptunium, and 4 plutonium ferromagnets with spin fluctuation theory originally developed for researches on itinerant ferromagnets in the 3 transition metals and their intermetallics. The applicability of the spin fluctuation theory to the actinide 5 system has been confirmed and the itinerant character of the 5f electrons is suggested in the actinide ferromagnets. In this conference, two results will be shown. One is the results of the analyses on 80 actinide ferromagnets and the other is the pressure dependence of the spin fluctuation parameters in UGe.
Yano, Kimihiko; Kitagaki, Toru; Washiya, Tadahiro; Miyamoto, Yasuaki; Ogawa, Toru
Progress in Nuclear Science and Technology (Internet), 5, p.225 - 228, 2018/12
According to the roadmap for decommissioning of Fukushima Daiichi NPS, fuel debris retrieval will start from 2021, after a decade from fuel debris generation. Fuel debris will stay in the reactors until the end of defueling. In addition, it is not hard to anticipate that storage is necessary for fuel debris removed from reactors. In order to consider such a post-accident operation for fuel debris, it is indispensable to discuss the states and characteristics of fuel debris during several decades. Therefore, JAEA directed R&D strategy on mid- and long-term behavior of fuel debris tentatively and is making a start of fundamental studies on this issue in corporation with the domestic universities and other research institutes.
Rai, D.*; Yui, Mikazu; Kitamura, Akira
Progress in Nuclear Science and Technology (Internet), 5, p.19 - 26, 2018/11
The objectives of this presentation are (1) to describe the solubility method, (2) to list desirable criteria of the solubility method so that the reader can recognize which studies have been done in a way that yields quality information, (3) to present an example of how to use the evaluation criteria, and (4) to provide a few examples of future research needs where the solubility method is ideally suited and the other methods are unsuitable for these investigations.
Suzuki, Eriko; Nakajima, Kunihisa; Osaka, Masahiko
Progress in Nuclear Science and Technology (Internet), 5, p.165 - 167, 2018/11
In severe accident condition, CsFeSiO could be formed by Cesium (Cs) chemisorption onto reactor structural materials. For evaluation of re-vaporization behavior, effect of atmosphere on the vaporization behavior of CsFeSiO at high temperature was investigated by thermal gravimetric-differential thermal analyzer (TG-DTA) experiments. As a result, it was found that vaporization of CsFeSiO in reducing atmosphere (Ar-5%H) started at relatively low temperature, about 800C, compared with in atmosphere containing HO (Ar-5%H-5%HO). It was inferred that a possible chemical reaction for the weight loss at around 800C would occurred by the decomposition of CsFeSiO into volatile Cs vapor species under H.
Ishidera, Takamitsu; Tachi, Yukio; Akagi, Yosuke*; Ashida, Takashi
Progress in Nuclear Science and Technology (Internet), 5, p.221 - 224, 2018/11
In Fukushima Daiichi Nuclear Power Station, radionuclides are removed from contaminated water by the decontamination system using zeolite. In this study, sorption properties of U and Np on zeolite were investigated by batch sorption experiments to obtain fundamental information for predicting the radionuclides inventory. High distribution coefficients were observed for U in the simulated sea water diluted 10 times by deionized water. In contrast, low distribution coefficient of U was observed in simulated sea water. Low distribution coefficients were observed for Np independent of simulated sea water concentration. Batch sorption experiments of U carried out as functions of sodium ion and total inorganic carbon concentration suggested that the distribution coefficient of U was strongly affected by the total inorganic carbon concentration. This result suggests that aqueous species of radionuclides and their sorption behavior need to be considered to estimate the inventory of radionuclides in zeolite.
Nakahara, Masaumi; Sano, Yuichi; Abe, Hitoshi
Progress in Nuclear Science and Technology (Internet), 5, p.52 - 55, 2018/11
For evaluating the secular change of Pu evaporator made of Zr in the commercialized nuclear fuel reprocessing plant, electrochemical experiments were carried out with Pu nitrate solutions. The open circuit potentials of Zr increased with increasing Pu, HNO concentrations and temperature. However, these experimental results imply that Zr has high corrosion resistance in Pu nitrate solutions.
Tachi, Yukio; Ochs, M.*
Progress in Nuclear Science and Technology (Internet), 5, p.229 - 232, 2018/11
Various types of post-accident radioactive waste have been generated from cleanup and decommissioning activities at the Fukushima Daiichi Nuclear Power Plant. For the disposal of these wastes, perturbation effects resulting from co-existing substances (e.g., organic substances, boron, and salts) are needed to be considered. Such co-existing substances may influence on the radionuclide sorption parameters for the safety assessment of the disposal systems. The present study focuses on developing the methodology to quantify sorption parameters by considering such perturbation effects and illustrating example calculations regarding the sorption reduction factors (SRFs) due to the presence of organic ligands (ISA) for cement systems. Three approaches for the derivations of SRFs for cement-Am-ISA case were compared. These options should be applied as a stepwise manner according to the data availability for the perturbation effects resulting from the co-existing substances.
Ochs, M.*; Vriens, B.*; Tachi, Yukio
Progress in Nuclear Science and Technology (Internet), 5, p.208 - 212, 2018/11
The clean-up activities related to the accident at the Fukushima Nuclear Power Plant give rise to several types of wastes containing cementitious materials, such as concrete. Further, the use of cement-based barriers may be considered, due to their favorable and stable chemical properties, including their ability to sorb or incorporate radionuclides. Wastes from Fukushima are expected to contain substances that can have perturbing effects on retention, especially organic complexing substances, boron, and chloride salts. The present study focuses on a methodology for quantifying the retention behaviour of UVI) and U(IV) in cement materials of different degradation and in the presence of organics, boron, and salts on the basis of available literature information. A stepwise approach is proposed and illustrated for Kd setting for U(VI) and U(IV).
Akagi, Yosuke*; Kato, Hiroyasu*; Tachi, Yukio; Sakamoto, Hiroyuki*
Progress in Nuclear Science and Technology (Internet), 5, p.233 - 236, 2018/11
A large amount of radioactive contaminated concrete will be generated from the decommissioning in the Fukushima Dai-ichi Nuclear Power Plant (NPP). For developing the plans of decommissioning and waste management including decontamination and disposal, it is important to estimate radionuclides inventory and concentration distribution in the concrete materials. In this study, effective diffusivities (De) and distribution coefficients (Kd) of HTO, Cs, I and U in OPC mortar were measured by through-diffusion and batch sorption experiments. De values derived were in the sequence of HTO, I, Cs, U, implying that cation exclusion effects may be important mechanisms in OPC mortar. Kd values derived by batch tests were higher by more than one order of magnitude than the diffusion-derived Kd values, indicating that crushing of samples had a strong influence on sorption. Diffusion and sorption mechanisms in OPC mortar were evaluated to predict the penetration behavior of these radionuclides.
Nakajima, Kunihisa; Suzuki, Eriko; Miyahara, Naoya; Osaka, Masahiko
Progress in Nuclear Science and Technology (Internet), 5, p.168 - 170, 2018/11
Chemical interaction between cesium (Cs) vapor and stainless steel (SS) surface known as chemisorption can cause a significant amount of Cs retention on the inner surfaces within the reactor pressure vessel during a light water reactor severe accident (SA). Although the chemisorption is known to be influenced with temperature and atmosphere, their dependancies are not yet fully understood. Therefore, the Cs chemisorption behaviours under mixed gases of steam and hydrogen were experimentally examined to contribute to a better understanding of the chemisorption behaviours under various atmospheres experienced during the SA at the Fukushima Daiichi Nuclear Power Station. As a result, it was found that the deposited amounts of Cs onto the SS in the steam-containing atmosphere were much higher than those in the no steam atmosphere. It was considered that Cs revaporization from a chemisorbed product was one of the reasons why the deposited amounts under the reducing atmosphere decreased.
Simonnet, M.; Miyazaki, Yuji; Suzuki, Shinichi; Yaita, Tsuyoshi
Progress in Nuclear Science and Technology (Internet), 5, p.66 - 69, 2018/11
Okamoto, Yoshihiro; Takano, Masahide
Progress in Nuclear Science and Technology (Internet), 5, p.200 - 203, 2018/11
Chemical state of some simulated corium debris samples containing uranium (fuel), zirconium (fuel cladding), iron (structure material), calcium (cement) and lanthanides (fission products) was investigated by synchrotron radiation based extended X-ray absorption fine structure (EXAFS) analysis. The local structure of uranium for the simulated debris was classified into fluorite UO structure and C-type structure (stabilized cubic). The UZrFeCaO sample, which consists of single phase (C-type), shows slightly shorter U-O distance. It can be concluded that the sample contains pentavalent uranium. The local structure of zirconium for U-Zr-O and U-Zr-Fe-O systems was very close to tetragonal ZrO, while that of zirconium changed to CSZ (calcia stabilized cubic) by adding calcium.
Fujimori, Shinichi; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*
Progress in Nuclear Science and Technology (Internet), 5, p.82 - 85, 2018/11
Hayashi, Hirokazu; Chiba, Rikiya*
Progress in Nuclear Science and Technology (Internet), 5, p.196 - 199, 2018/11
Uranium-free nitride fuel has been chosen as the first candidate for transmutation of long-lived minor actinides (MA: Np, Am, Cm) using sub-critical accelerator-driven system (ADS) under the double strata fuel cycle concept by Japan Atomic Energy Agency (JAEA). Dissolution behavior of ZrN-based nitrides in nitric acid is examined using lanthanides as surrogate materials of TRU elements. Chemical analysis of the ZrN-based lanthanide nitrides dissolved in nitric acid is also carried out.
Kitagaki, Toru; Ikeuchi, Hirotomo; Yano, Kimihiko; Ogino, Hideki; Haquet, J.-F.*; Brissonneau, L.*; Tormos, B.*; Piluso, P.*; Washiya, Tadahiro
Progress in Nuclear Science and Technology (Internet), 5, p.217 - 220, 2018/11
Sekiguchi, Tetsuhiro; Yokoyama, Keiichi; Uozumi, Yuki*; Yano, Masahiro; Asaoka, Hidehito; Suzuki, Shinichi; Yaita, Tsuyoshi
Progress in Nuclear Science and Technology (Internet), 5, p.161 - 164, 2018/11
For nuclear transmutation of cesium-135 (Cs), which is long-lived fission product, we are developing selective absorbent which takes only Cs atom in, but does not CsI. In this study, absorbing property of Cs atom onto the surface of fullerene (C) film has been investigated using synchrotron-based angle-dependent X-ray photoelectron spectroscopy (XPS). The results were compared with those of CsI. It was found that Cs penetrates into C deep bulk. In contrast, CsI deposits on shallow surface. Furthermore, XPS spectra were measured as a function of Ar-sputtering time in order to know Cs concentration profiles in deep region. Results showed that Cs penetrates into deep region of several hundreds .
Shimada, Taro; Takubo, Kazuya*; Takeda, Seiji; Yamaguchi, Tetsuji
Progress in Nuclear Science and Technology (Internet), 5, p.183 - 187, 2018/11
After fuel debris is removed from the reactor containment vessel at Fukushima Daiichi NPS (1F) and collected in waste containers in the future, the waste containers will be disposed at a deep geological repository. The uranium inventory and uranium-235 (U) enrichment of the fuel debris are larger than those of high-level vitrified wastes which are produced from liquid waste during reprocessing of spent nuclear fuels. Therefore, there is a possibility not to be excluded that a criticality occurs in the geological media where the uranium precipitates at the far-field from the repository, after the uranium located in the repository is dissolved by groundwater. In this study, we calculated the quantity of uranium precipitated at the natural barrier, and studied dimension of uranium deposited in the natural barrier and carried out the criticality analysis.
Kofuji, Hirohide; Watanabe, So; Takeuchi, Masayuki; Suzuki, Hideya; Matsumura, Tatsuro; Shiwaku, Hideaki; Yaita, Tsuyoshi
Progress in Nuclear Science and Technology (Internet), 5, p.61 - 65, 2018/11
Nakamura, Shota*; Sakakibara, Toshiro*; Shimizu, Yusei*; Kittaka, Shunichiro*; Kono, Yohei*; Haga, Yoshinori; Pospisil, J.; Yamamoto, Etsuji
Progress in Nuclear Science and Technology (Internet), 5, p.123 - 127, 2018/11