Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
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.
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, ,
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.
Meier, R.; Kitagaki, Toru; Kozai, Naofumi; Fellhauer, D.*; Kobayashi, Taishi*; Onuki, Toshihiko
no journal, ,
Yamaguchi, Akiko; Kuribara, Yuichi; Okumura, Masahiko; Takahashi, Yoshio*
no journal, ,
no abstracts in English
Sugiura, Yuki; Ishidera, Takamitsu; Suyama, Tadahiro*; Okazaki, Mitsuhiro*; Hamamoto, Takafumi*; Ishida, Keisuke*; Tachi, Yukio
no journal, ,
Iwatsuki, Teruki; Ishii, Eiichi
no journal, ,
The paper reviews the applicable knowledge of the migration properties in deep underground gained by R&D in Mizunami and Horonobe URL. Summing up the major migration path, it is necessary to consider the fracture continuity / connectivity of hundreds of meters in granite of Mizunami area, while several hundred meters in the shallow part of sedimentary rock and of tens m scale in the deep part of Horonobe. On the other hand, it was also demonstrated that analogue elements are practically immobile in rock masses and closed galleries.
Ozaki, Yusuke; Iwatsuki, Teruki; Onoe, Hironori
no journal, ,
In this study, we evaluate the effect of shotcrete on the geo-environment after closure of drift. The shotcrete is known to be dissolved into water and change the groundwater chemistry. The detail of chemical process of dissolution of shotcrete is analyzed with the in-situ groundwater collected during GREET experiment in MIU. In addition, reactive transportation simulation is performed to predict the movement of high pH groundwater affected by dissolution of shotcrete. Our simulation results show that the movement of high pH water is slow owing to the diffusive condition after closure of drift under our simulation condition.
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, ,
Havlov, V.*; Zuna, M.*; Brzda, L.*; Rosendorf, T.*; Sammalj
rvi, J.*; Nenonen, V.*; Siitari-Kauppi, M.*; Sasao, Eiji; Gvo
d
k, L.*
no journal, ,
Anion exclusion is a process that has been widely observed mainly with concern to clay materials. However, this process has also been observed in some types of crystalline rock. Because anion exclusion exerts the impact on migration in the most constricted parts of nanometre-scale pores, this study focused on H, 
Cl and 
I diffusion together with the characterisation of the rock pore structure of magmatic and metamorphic rocks. Both the anionic species exhibited lower diffusion coefficients than that of H, thus indicating anionic exclusion mainly in the metamorphic rocks studied. The De values for the anions in the metamorphic rocks differed from those in the magmatic rocks by around one order of magnitude. The difference between the De values for magmatic and metamorphic rocks is clearly supported by pore structure visualisation by autoradiography. Preliminary results showed decreasing accessible porosity for anionic species rather than decreasing pore diffusion coefficients.
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.
Fujiwara, Kenso; Sasaki, Takayuki*; Matoba, Daisuke*; Iijima, Kazuki
no journal, ,
Depth profiles of radionuclides atmospheric discharged to the environment of Fukushima was obtained nearby the Fukushima Daiichi Nuclear Power Station (FDNPS). According to the profiles, it was suggested that deposition of Pu-238 and Cs-137 was mostly caused by atmospheric discharge by the FDNPS accident, however, in the case of Pu-239+240, it is necessary to consider the effect of global fallout. For understanding on the migration behaviour of radionuclide, it is necessary to obtain the profiles attributed by the accident and global fallout. In this study, in order to clarify the profile of soil, time dependence of depth profile of Cs and Pu in the soil outside of FDNPS site was measured. Based on the results of this study, it was confirmed that Pu and Cs will not be transferred significantly in the soil over several years. In the case of Pu, concentration of fallout and discharge was calculated. This data is considered to be useful for the safety assessment of waste in FDNPS, especially, measurement of other nuclides can also show the utility of transport ratio based on Cs concentration.
Shimoyama, Iwao; Baba, Yuji*
no journal, ,
Management of radioactive contaminated soil is an unsolved problem after the nuclear incident in Fukushima, but soil decontamination is generally difficult due to the existence of micaseous clay minerals in which radiocesium is strongly fixed. Cesium-free mineralization (CFM) can remove Cs from the soil through the conversion process from clay minerals to other minerals and the choice of reactant is critically important for this method. Because CaCl has higher decontamination efficiency than CaCO
and Ca(OH) and facilitates phase transformation of clay minerals around 700
C, it is deduced that Cl has a catalytic effect on phase transformation, however, the detail is not clear. In this work, Cs-sorbed weathered biotite (WB) was used as a model soil and chemical bonding states of Cl was studied using X-ray absorption spectroscopy and molecular orbital calculations. We clarified that Cl interacted with WB at 400C and Cl
and higher valent Cl sites were formed by bonding with O in WB besides Cl
sites in the early stage of the reaction. Because formation of Cl-O bonds can destabilize the silica network, Cl can facililate decomposition and phase transformation of WB at moderate temperatures.
Aoyagi, Noboru; Motokawa, Ryuhei; Saito, Takumi*; Okumura, Masahiko; Ikeda, Atsushi
no journal, ,
Iijima, Kazuki; Fujiwara, Kenso; Matoba, Daisuke*; Sasaki, Takayuki*
no journal, ,
Depth profiles of radionuclides discharged to the environment of Fukushima was obtained in the forest soil just nearby the Fukushima Daiichi Nuclear Power Station (FDNPS). According to characteristics of the depth profile, Pu-238 was originated from the FDNPS accident, while Pu-239+240 was mainly originated from global fallout. Comparing depth profiles attributed by the accident and global fallout can give understanding on the migration behavior of Pu in subsurface soil during decades. In this study, advection-dispersion model was applied to evaluate the depth profiles of Pu isotopes. The Kd values for global fallout Pu-239+240 agreed with those of Fukushima Pu-238 within around factor 3. Therefore, migration behavior of Pu could be understood by the advection-dispersion model.