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Martin, A.*; Fukatsu, Yuta; Tachi, Yukio; Ishida, Keisuke*; Muuri, E.*; Siitari-Kauppi, M.*; Havlov
, V.*; Vokal, A.*
no journal, ,
Takeda, Masaki; Ishii, Eiichi; Ono, Hirokazu; Tachi, Yukio; Ito, Tsuyoshi*; Nemoto, Kazuaki*
no journal, ,
Tachi, Yukio; Takeda, Masaki; Ono, Hirokazu; Ito, Tsuyoshi*; Sato, Tomofumi*; Nemoto, Kazuaki*
no journal, ,
Ochs, M.*; Dolder, F.*; Tachi, Yukio
no journal, ,
Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Mitachi, Katsuaki*; Watanabe, Takayoshi
no journal, ,
Kurikami, Hiroshi; Malins, A.; Niizato, Tadafumi; Iijima, Kazuki; Tsukada, Hirofumi*
no journal, ,
This study examined the evolution of reversibly sorbed 
Cs in forest soil using a vertical transport model considering kinetic sorption. The simulated distributions and physicochemical forms of Cs were consistent with measurements, indicating the modelling approach was reasonable. The results suggest that Cs concentrations in wild animals are somewhat linked with the concentration of reversibly sorbed Cs in forest soil.
Kozai, Naofumi; Suzuki, Shinichi; Sakamoto, Fuminori; Onuki, Toshihiko
no journal, ,
A fraction of radiocesium (Cs) released by the Fukushima Daiichi Nuclear Power Plant accident was accumulated in sewage sludge ash (SSA). It was previously reported that more than 80% of Cs is fixed in iron oxides of SSA and approximately 10% of Cs is tightly fixed in unidentified amorphous silicon oxides of SSA. This study reports that silicon in paper flowing in sewage and that in organic flocculant added to sewage at sewage treatment plants are origin of the silicon in SSA. Next, to contribute to developing measures for SSA disposal, we prepared geopolymer and cement solidified bodies containing SSA and evaluated their characteristics. We report a high barrier performance of geopolymer solidified bodies.
Yamaguchi, Akiko; Kuribara, Yuichi; Okumura, Masahiko; Takahashi, Yoshio*
no journal, ,
no abstracts in English
Suno, Hiroya; Machida, Masahiko; Dohi, Terumi; Omura, Yoshihito*; Sasaki, Yoshito
no journal, ,
Complexation of biomolecules with radiocesium is known to play an important role in the accumulation and migration of radioactivity on the organic matter in forests. In this work, we identify typical molecules forming a metal complex in the forest organic matter and carry out atomistic analyses by performing quantum mechanical calculations in order to understand the alkali metal cation complexation selectivity of these organic molecules. Among these molecules, of particular interest are norbadione A (C
H
O
), a primary pigment molecule present in mushrooms, oxalic acid (C
HO
), atranorin (C
HO
), lecanoric acid (C
H
O
), and usnic acid (CHO), main secondary metabolites in lichens.
Takano, Masahide; Hirano, Hiroyasu; Yano, Kimihiko; Mitsugi, Takeshi; Washiya, Tadahiro
no journal, ,
Fuel debris was generated in the reactor core in the Fukushima Daiichi Nuclear Power Station (hereafter, 1F) where the severe accident occurred in March, 2011. The information of debris properties is essential in the entire course of the decommissioning work: debris removal process, storage, treatment and disposal. The Japan Atomic Energy Agency (JAEA) is a member of International Research Institute for Nuclear Decommissioning (IRID) who has been conducting studies to estimate the fuel debris properties and to contribute to the decommissioning. In this conference, outline of these research and development in CLADS will be reported.
Tanaka, Kazuya; Kozai, Naofumi; Yamaji, Keiko*; Masuya, Hayato*; Grambow, B.
no journal, ,
Radium-226, a descendant nuclide of 
U, is of serious concern in Ningyo-toge Environmental Engineering Center because its radioactive concentration in mining wastewater exceeds the effluent standard. In this study, we examined Ba and Sr adsorption on biogenic Mn oxide as a preliminary surrogate for Ra adsorption. Both Ba and Sr show the dependence of adsorption on NaCl concentration. Overall, Ba gave an order of magnitude higher Kd values than Sr. Adsorption behavior of Ra would be similar to that of Ba in terms of ionic radius. Barium showed Kd value greater than 10
in 10 mM NaCl solution, similar to the ionic strength of the fresh water system in the Ningyo-toge center. Therefore, it is expected that the biogenic Mn can work effectively for removal of Ra from mining wastewater.
Kimuro, Shingo; Terashima, Motoki; Tachi, Yukio; Kitatsuji, Yoshihiro; Miyakawa, Kazuya; Akiyama, Daisuke*; Sato, Nobuaki*; Kirishima, Akira*
no journal, ,
Humic acid is confirmed to be present even in deep underground where radioactive wastes are planned to be disposed. Although the characteristic properties and reaction mechanism of humic acid are strongly affected by its origin, the reaction enthalpy and entropy for groundwater humic acid complexation are only estimated values obtained from the equilibrium constants at different temperature despite these thermodynamic quantities is necessary for the discussion of reaction thermodynamics. In this study, the thermodynamic quantities of the complexation of deep groundwater humic acid at Horonobe, Hokkaido, Japan with copper (II) and uranyl (VI) ion were determined by the combination of the potentiometry and calorimetry to cultivate a better understanding of the reaction mechanism. By the comparison of thermodynamic quantities with typical humic acid and simple organic acid, the characteristic reaction mechanism of Horonobe humic acid was revealed. In addition, thermodynamic equilibrium calculations based on the determined thermodynamic quantities were performed for the discussion of the impact of humic acid complexation and the origin of humic acid in the migration of radionuclide.
pelletMoroi, Yuriko*; Kirishima, Akira*; Akiyama, Daisuke*; Sato, Nobuaki*; Kitamura, Akira; Kimuro, Shingo
no journal, ,
Development of spent nuclear fuel direct disposal system is one of important options in Japan to maintain flexibility of the back-end strategy of nuclear fuel cycle. Other countries like Sweden and Finland advance in research and development of the direct disposal system. However, it is known that some groundwater in Japan contains higher concentration of carbonate ion than that in Sweden or Finland. Therefore, the effect of carbonate ion on the dissolution rate of UO has to be discussed to evaluate feasibility of the direct disposal system in Japan.
Sasamoto, Hiroshi; Arthur, R. C.*; Alt-Epping, P.*; Tachi, Yukio
no journal, ,
The present study performed an interpretation of natural tracers (non or weakly sorption elements) profiles of groundwater observed in the boreholes drilled from the surface around the Horonobe Underground Laboratory based on the transport processes of advection and diffusion. In the interpretation, due to several uncertainty ranges for transport parameters in initial and boundary conditions, sensitivity analyses considering the relevant model parameters defined uncertainty limits were also conducted to evaluate the plausible parameter sets and conditions to be compatible with observations.
Fukatsu, Yuta; Ito, Tsuyoshi*; Tachi, Yukio; Ishida, Keisuke*; Martin, A.*
no journal, ,
Chen, Y.; Sawaguchi, Takuma
no journal, ,
Sorption of boron in compacted Na-montmorillonite was studied for a better understanding of the boron migration behavior. Boron adsorption at various pH and ionic strength conditions was investigated by batch studies. Sorption distribution ratio value (K
[m
/kg]) was found to be at the order of magnitude of -3. At fixed pH, sorption can be described using Freundlich isotherm expressions. Boron sorption generally increased with pH. Above about pH 8, however sorption decreased. It was assumed that adsorption was via ligand exchange with aluminol groups at clay surfaces. Both charges of adsorbent and adsorbate were taken into account to explain the pH effects.
Okumura, Masahiko; Kerisit, S.*; Bourg, I.*; Lammers, L.*; Ikeda, Takashi*; Sassi, M.*; Rosso, K.*; Machida, Masahiko
no journal, ,
no abstracts in English
Sakamoto, Fuminori; Kozai, Naofumi; Guido-Garcia, F.; Kimura, Tatsuki; Grambow, B.
no journal, ,
Soil microorganisms are known to remove a fraction of tightly fixed radiocesium and make it bioavailable. In this study, we attempted to nondestructively recover available radiocesium from soil using microorganisms instead of plants. Microbial activity was tested to form bioavailable radiocesium by the comparing the addition of nutrients and microbicide. Powdered minerals, a water absorbent material, and paper towels were packed in a fine mesh cloth bag (mineral bag) with a size of 50 cm 
50 cm. The radiocesium concentration analysis revealed that the surface soil contained approximately 0.3-1.2 Bq/g. The mineral mat was replaced with a new one every two weeks. Two control experiments were established: one with 1 L of nutrient solution to activate microorganisms, and another with sodium hypochlorite aqueous solution to suppress microbial activity. These solutions were added every week. After eight weeks, radiocesium concentrations of the top soil and in the soil core were measured. The accumulative radiocesium concentration in the four mats after eight weeks was within 4.210
and 9.010 Bq, indicating that the mats indeed absorbed radiocesium from soil. The driving force of upward migration of radiocesium is thought to be soil water flow due to continuous water absorption from soil by the mat and evaporation from itself. These results suggest that cesium upward migration flow along with water is a behavior expected to happen in the environment.
Kimura, Tatsuki; Guido-Garcia, F.; Kozai, Naofumi; Zhang, S.*; Yamaji, Keiko*; Yu, Q.*; Grambow, B.
no journal, ,
To understand bacterial ability to dissolve clay minerals, we isolated siderophore-producing bacteria from white clover roots grown in south Osaka, Japan. The ability to produce siderophores was evaluated by CAS plate method. llite, biotite, vermiculite and nontronite were used for testing as clay minerals. Three different bacteria strains were cultivated. Bacteria cells were centrifuged and washed before inoculation tests. Fifty mg dry weight of bacteria were inoculated into 100 mL modified Balland media and 100 mg of each clay mineral added. The suspension was sampled and new media was added. The concentrations of iron, aluminium and silicon were determined by ICP-OES. The presence of organic molecules was determined by SEC-ICP-OES. The peaks of siderophores were determined using the 405 nm absorbance. As a result, siderophore producing bacteria are able to dissolve clay. This suggests that the effect of siderophore on cesium dissolution is an indirectly process.
Cs uptake by lentinula edodes (shiitake) mushroomsGuido-Garcia, F.; Sakamoto, Fuminori; Kozai, Naofumi; Grambow, B.; Devid, K.*
no journal, ,
The uptake of Cs by fungi has been thought to be similar to the uptake of K due to their chemical similarities. In this research we aimed to evaluate the impact of different concentrations of K in Cs uptake during mushrooms growth, as well as determine the spatial distribution of both within fruit bodies. Lentinula edodes (shiitake) was used as a model organism due to their capacity to produce fruit body. Preliminary results have shown that the concentrations of Cs in the obtained mushroom samples from mushroom bed did not show any clear relationship to the different concentrations of added K. Higher concentrations of Cs were observed in pileus than in stem, consistently. The results of Cs and K mapping did not show a significant spatial variation. This result suggest that Cs and K are distributed evenly, and that there is no specific or selective binding site for cesium.