Ito, Ayumi*; Yamashita, Susumu; Tasaki, Yudai; Kakiuchi, Kazuo; Kobayashi, Yoshinao*
Journal of Nuclear Science and Technology, 60(4), p.450 - 459, 2023/04
Suzuki, Tomoya*; Otsubo, Ukyo*; Ogata, Takeshi*; Shiwaku, Hideaki; Kobayashi, Toru; Yaita, Tsuyoshi; Matsuoka, Mitsuaki*; Murayama, Norihiro*; Narita, Hirokazu*
Separation and Purification Technology, 308, p.122943_1 - 122943_7, 2023/03
HNO leaching is used in recycling Pd metal from spent products that primarily contain Ag, and most Pd residues are separated from solutions containing Ag(I). However, a small amount of Pd(II) often remains in these Ag(I) solutions. Therefore, the separation of Pd(II) and Ag(I) in HNO solutions is essential to promote efficient Pd recycling. In this study, the separation of Pd(II) and Ag(I) in HNO solutions was investigated using four N-donor-type adsorbents functionalized with amine (R-Amine), iminodiacetic acid (R-IDA), pyridine (R-Py), or bis-picolylamine (R-BPA). R-Amine, R-IDA, and R-Py selectively adsorbed Pd(II) over Ag(I), Cu(II), Ni(II), and Fe(III) from HNO solutions (0.3-7 M), but R-Amine exhibited a lower Pd adsorption efficiency. In contrast, 90% of Pd(II), Ag(I), and Cu(II) were adsorbed by R-BPA over the entire range of HNO concentrations. Structural analyses of the adsorbed metal ions using Fourier transform infrared spectroscopy and extended X-ray absorption fine structure spectroscopy revealed the separation mechanisms of the N-donor-type adsorbents. Pd(II) adsorption on R-IDA, R-Py, and R-BPA occurred via Pd(II) coordination of the functional groups (iminodiacetic acid, pyridine, and bis-picolylamine, respectively), whereas that on R-Amine occurred via anion exchange of NO with [Pd(NO)]. The coordinative adsorption mechanisms resulted in the higher Pd(II) adsorption behaviors of R-IDA, R-Py, and R-BPA. HCl (5.0 M) and thiourea (0.1 M) eluents desorbed 83% of Pd(II) from R-IDA and 95% from R-Py, respectively. R-Py was the most effective Pd(II) adsorbent based on adsorption selectivity and desorption efficiency.
Akiyama, Daisuke*; Kusaka, Ryoji; Kumagai, Yuta; Nakada, Masami; Watanabe, Masayuki; Okamoto, Yoshihiro; Nagai, Takayuki; Sato, Nobuaki*; Kirishima, Akira*
Journal of Nuclear Materials, 568, p.153847_1 - 153847_10, 2022/09
FeUO, CrUO, and FeCrUO are monouranates containing pentavalent U. Even though these compounds have similar crystal structures, their formation conditions and thermal stability are significantly different. To determine the factors causing the difference in thermal stability between FeUO and CrUO, their crystal structures were evaluated in detail. A Raman band was observed at 700 cm in all the samples. This Raman band was derived from the stretching vibration of the O-U-O axis band, indicating that FeCrUO was composed of a uranyl-like structure in its lattice regardless of its "x"' value. Mssbauer measurements indicated that the Fe in FeUO and FeCrUO were trivalent. Furthermore, FeCrUO lost its symmetry around Fe with increasing electron densities around Fe, as the abundance of Cr increased. These results suggested no significant structural differences between FeUO and CrUO. Thermogravimetric measurements for UO, FeUO, and CrUO showed that the temperature at which FeUO decomposed under an oxidizing condition (approximately 800 C) was significantly lower than the temperature at which the decomposition of CrUO started (approximately 1250 C). Based on these results, we concluded that the decomposition of FeUO was triggered by an "in-crystal" redox reaction, i.e., Fe U Fe U, which would not occur in the CrUO lattice because Cr could never be reduced under the investigated condition. Finally, the existence of Cr in FexCrUO effectively suppressed the decomposition of the FeCrUO crystal, even at a very low Cr content.
Liu, J.; Dotsuta, Yuma; Sumita, Takehiro; Kitagaki, Toru; Onuki, Toshihiko; Kozai, Naofumi
Journal of Radioanalytical and Nuclear Chemistry, 331(6), p.2785 - 2794, 2022/06
Remnant nuclear fuel debris in the damaged nuclear reactors at the Fukushima Daiichi Nuclear Power Plant (FDNPP) has contacted the groundwater containing microorganisms for over ten years. Herein, we report the possibility of bacterial alteration of fuel debris. We investigated the physical and chemical changes of fuel debris simulants (FDS) in the powder and pellet forms via exposure to two ubiquitous bacteria, Pseudomonas fluorescens and Bacillus subtilis. In the experiments using FDS composed of the powders of Fe(0), solid solution of CeO and ZrO, and SiO, Ce, Zr, and Si were hardly dissolved, while Fe was dissolved, a fraction of the dissolved Fe was present in the liquid phase as Fe(II) and Fe(III), and the rest was precipitated as the nano-sized particles of iron (hydr)oxides. In the experiment using P. fluorescens and FDS pellet pieces prepared by melting the Fe(0) particles and solid solution of CeO and ZrO, the bacteria selectively gathered on the Fe(0) particle surface and made corrosion pits. These results suggest that bacteria in groundwater corrode the iron in fuel debris at FDNPP, change fuel debris into porous one, releasing the nano-sized iron (hydr)oxide particles into the water.
Momma, Yuichiro*; Sakairi, Masatoshi*; Ueno, Fumiyoshi; Otani, Kyohei
Zairyo To Kankyo, 71(5), p.133 - 137, 2022/05
The effect of the corrosion inhibitor on the corrosion of steel under a thin solution layer was investigated. As a result of forming a thin solution layer with a thickness of 1.0-0.2 mm on the specimen, adding a mixed solution of sodium molybdate and aluminum lactate as a corrosion inhibitor, and performing electrochemical measurement, the corrosion inhibitor suppresses the anodic reaction. And in the thin solution layer, it was suggested that the morphology of the protective layer structure by the corrosion inhibitor changed according to the amount of liquid as compared with the bulk immersion.
Momma, Yuichiro*; Sakairi, Masatoshi*; Ueno, Fumiyoshi; Otani, Kyohei
Zairyo To Kankyo, 71(4), p.121 - 125, 2022/04
The effect of solution layer thickness on the atmospheric corrosion of carbon steel was investigated using novel devices fabricated by a 3D printer. These novel devices allowed us to control the solution layer thickness precisely. Potentiodynamic polarization measurements were performed under thickness-controlled solution layer, and oxygen diffusion limiting current density () and anodic current density () were measured. As the solution layer become thinner, increased and decreased. This result indicates that corrosion accelerates when the solution layer becomes thinner. The diffusion coefficient of oxygen was calculated as 3.2010 cm s from the relationship between and solution layer thickness, and the critical diffusion thickness was estimated to be 0.87 mm.
Kitagaki, Toru; Yoshida, Kenta*; Liu, P.*; Shobu, Takahisa
npj Materials Degradation (Internet), 6(1), p.13_1 - 13_8, 2022/02
Wada, Yuki; Furuichi, Noriyuki*; Tsuji, Yoshiyuki*
European Journal of Mechanics B, Fluids, 91, p.233 - 243, 2022/01
McGrady, J.; Kumagai, Yuta; Watanabe, Masayuki; Kirishima, Akira*; Akiyama, Daisuke*; Kitamura, Akira; Kimuro, Shingo
RSC Advances (Internet), 11(46), p.28940 - 28948, 2021/08
Hemmi, Ko; Walker, A.*; Yamaguchi, Tetsuji
Radiochimica Acta, 109(7), p.539 - 546, 2021/07
Plutonium(IV) sorption onto quartz in carbonate solutions was systematically investigated under anaerobic conditions to analyze the sorption behaviors of Pu(IV) with a non-electrostatic model (NEM). Pu(IV) sorption data was obtained from batch sorption experiments as a function of pH and carbonate concentration. The Pu(IV) sorption onto quartz showed similar tendencies to Th(IV), which is considered to be chemically analogous as a tetravalent actinoid. The distribution coefficient, d, of Pu(IV) onto quartz showed inverse proportionality to the square of the total carbonate concentration under the investigated pH conditions of 8 to 11. The modeling study, however, revealed a Th(IV) sorption model, which is SOTh(OH) and SOThOH(CO), could not be applied to simulate the Pu(IV) sorption onto quartz. It was inferred that the electrostatic repulsion between negatively charged ligands limited the formation of SOM(OH) and SOMOH(CO) for Pu(IV) with smaller ionic radii than Th(IV). The Pu(IV) sorption model was developed as SOPu(OH) and SOPu(OH). In addition, data of Pu(IV) sorption onto muscovite was obtained in order to be compared with data for quartz.
Nakanishi, Ryuzo; Oba, Hironori; Saeki, Morihisa; Wakaida, Ikuo; Tanabe, Rie*; Ito, Yoshiro*
Optics Express (Internet), 29(4), p.5205 - 5212, 2021/02
Laser-induced breakdown spectroscopy (LIBS) combined with liquid jets was applied to the detection of trace sodium (Na) in aqueous solutions. The sensitivities of two types of liquid jets were compared: a liquid cylindrical jet with a diameter of 500 m and a liquid sheet jet with a thickness of 20 m. Compared with the cylindrical jet, the liquid sheet jet effectively reduced the splash from the laser-irradiated surface and produced long-lived luminous plasma. The limit of detection (LOD) of Na was determined to be 0.57 g/L for the sheet jet and 10.5 g/L for the cylindrical jet. The LOD obtained for the sheet jet was comparable to those obtained for commercially available inductively coupled plasma emission spectrometers.
Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*
JAEA-Review 2020-039, 59 Pages, 2021/01
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 FY2019. 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 FY2019. We have developed an imaging camera with a position resolution of less than approximately 10 m to monitor alpha dust in the nuclear plant during the decommissioning process, because the operators avoid to drawing in such dusts. Moreover, we have developed real-time monitor system with optical fiber and scintillator under high dose-rate condition.
Kobayashi, Takuya; Kawamura, Hideyuki; Kamidaira, Yuki
Nihon Genshiryoku Gakkai-Shi ATOMO, 62(11), p.635 - 639, 2020/11
It is important to predict the dispersion of radioactive materials released into the ocean due to nuclear accidents in the surrounding ocean of the east Asian countries. The Japan Atomic Energy Agency developed a Short-Term Emergency Assessment system of Marine Environmental Radioactivity (STEAMER) based on an oceanic dispersion model. STEAMER quickly predicts the oceanic dispersion of radioactive materials in the surrounding ocean of the east Asian countries using the online prediction data of oceanic condition. We validated the predictability of the oceanic dispersion and demonstrated the improvement of the predictability using an ensemble prediction method. Moreover, we developed a high resolution model in the coastal region using a Regional Ocean Modeling System (ROMS).
JAEA-Review 2020-006, 261 Pages, 2020/09
A literature review was conducted on the increase in surface area of vitrified products of HLW due to the fracturing caused by cooling during glass pouring process and by mechanical impact, from the perspective of a parameter of the radionuclide release model in the performance assessment of geological disposal system studied overseas. The review was focused on the value of surface area increase factor set as a parameter in the model, the experimental work to evaluate an increase in surface area, and how the parameters on surface area were determined based on the experimental results. The surface area obtained from the experiments executed in Japan was also discussed in comparison with the overseas studies. On the basis of the investigation, the effects of various conditions on the surface area were studied, such as a diameter of vitrified product, cooling condition during and after the glass pouring, impact on vitrified products during their handling, environment after the closure of disposal facility, and others. The causes of fracturing are associated with the phenomena or events in the waste management process such as production, transport, storage, and disposal. The surface area increase factors set in the nuclide release model of the glass and their bases were reviewed. In addition, the measured values and the experimental methods for surface increase factors published so far were compared. Accordingly, the methods for measuring surface area as the bases were identified for these factors set in the models. The causes of fracturing and features of these factors were studied with respect to the relation with the waste management process. The results from the review and assessment can contribute to the expanding the knowledge for the conservative and realistic application of these factors to performance assessment, and to the developing and upgrading of safety case as a consequence.
Tamain, C.*; Bonato, L.*; Aupiais, J.*; Dumas, T.*; Guillaumont, D.*; Barkleit, A.*; Berthon, C.*; Solari, P. L.*; Ikeda, Atsushi; Guilbard, P.*; et al.
European Journal of Inorganic Chemistry, 2020(14), p.1331 - 1344, 2020/04
The molecular characterization based on multi-technique approach has led to major highlights on revealing the coordination environment of americium (Am) surrounded by citric acid (HCitH). The structure of the different complexes at pH 1 and 3 are described. These characterizations are made possible by the comparison of the americium-citric acid system with the americium-tricarballylic acid (one analogue of the citric acid without the alpha-hydroxo group).
Collaborative Laboratories for Advanced Decommissioning Science; Tohoku University*
JAEA-Review 2019-038, 57 Pages, 2020/03
JAEA/CLADS, 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. Among the adopted proposals in FY2018, this report summarizes the research results of the "Development of Imaging System with Ultra-high Spatial Resolution Aiming to Detect Alpha-dust". In the present study, we have developed a prototype of a system aiming to elucidate the behavior of alpha-dust generated at the time of debris retrieval. In this system, alpha-ray is first converted to visible light by novel scintillator. Then, imaging with ultra-high resolution will be possible using a lens and an Si-semiconductor camera (CMOS camera). Also, it will be possible to identify the species of alpha-ray emitting nuclides by unfolding of the spectra. The demonstration tests of the system will be conducted for dust samplers at the Plutonium Fuel Development Center, JAEA. In the development of the present system, it is important to use scintillator whose emission wavelength is sensitive to the CMOS camera as well as high emission scintillator. Considering these conditions, the key technology will be the improvement of the purity of crystals and optimization of the shapes of the materials including powers.
Irisawa, Keita; Garcia-Lodeiro, I.*; Kinoshita, Hajime*
Cement and Concrete Research, 128, p.105951_1 - 105951_7, 2020/02
This study investigated characteristics of a calcium aluminate cement modified with a phosphate (CAP) by changing an amount and concentration of mixing solution with sodium polyphosphate. When the amount of mixing solution was increased with a constant amount of sodium polyphosphate, an enhanced consumption of monocalcium aluminate was observed compared with gehlenite in calcium aluminate cement (CAC). Formation of gibbsite, Al(OH), was also increased as a hydration product in the CAP and the possible reduction of water in the amorphous gel phase. When the amount of mixing solution was increased with a constant concentration of sodium polyphosphate, the enhanced consumption of monocalcium aluminate was not observed. Neither gibbsite nor any other crystalline hydration products were identified in this series. In addition, unreacted sodium polyphosphate remained in the system. The increased formation of gibbsite and the possible reduction of water from the amorphous gel phase appears to contribute to the improvement of the microstructure in the products.
Ogata, Sho*; Yasuhara, Hideaki*; Aoyagi, Kazuhei; Kishida, Kiyoshi*
Proceedings of 53rd US Rock Mechanics/Geomechanics Symposium (USB Flash Drive), 6 Pages, 2019/06
Simonnet, M.; Barr, N.*; Drot, R.*; Le Naour, C.*; Sladkov, V.*; Delpech, S.*
Radiochimica Acta, 107(4), p.289 - 297, 2019/04
Yamada, Ryohei; Odagiri, Taiki*; Iwaoka, Kazuki*; Hosoda, Masahiro*; Tokonami, Shinji*
Radiation Environment and Medicine, 8(1), p.21 - 25, 2019/02
We evaluate radon/thoron and its progeny concentration using passive-type monitors using CR-39 plates. After exposure, it is necessary to do chemical etching for CR-39 plates. In the present study, we considered shortening of chemical etching time for CR-39 and enlargement of the track diameter (i.e. etch pit diameter) aiming for introduction of automatic counting system in the future. Optimum conditions were determined by changing solution concentration, solution temperature and etching time. As a result, the optimized conditions (concentration, temperature and etching time) were determined to be 8 M NaOH solution, 75 degrees Celsius and 10 hours. This result of etching time showed that the chemical etching was completed in less than half of conventional etching time. Furthermore, it was suggested that shorter etching time would be possible if we do not consider the enlargement of conventional track diameter.