Sawaguchi, Takuma; Tsukada, Manabu; Yamaguchi, Tetsuji; Mukai, Masayuki
Clay Minerals, 51(5), P. 815, 2016/12
ERRATUM; Effects of OH activity and temperature on the dissolution rate of compacted montmorillonite under highly alkaline conditions [Clay Minerals, vol.51, p.275 (2016), Corrected Fig. 7.]
Sawaguchi, Takuma; Tsukada, Manabu; Yamaguchi, Tetsuji; Mukai, Masayuki
Clay Minerals, 51(2), p.267 - 278, 2016/05
The dependences of the dissolution rate of compacted montmorillonite on activity of OH (a-) and temperature (T) were investigated. The dissolution rate of montmorillonite () in compacted pure montmorillonite, which was formulized as = 10 (a-) e, was higher than that in the compacted sand-bentonite mixtures: = 3500 (a-) e. The difference can be explained by considering the decrease in a- in the mixtures accompanied by dissolution of accessory minerals such as quartz and chalcedony. The dissolution rate model developed for pure montmorillonite is expected to be applied to bentonite mixtures if quantification of the decrease in a- is achieved somehow.
Ishigami, Tsutomu; Shimada, Taro; Seki, Masaya; Mukai, Masayuki
JAEA-Data/Code 2015-019, 122 Pages, 2015/12
In ensuring compliance with the criterion of site release as the final stage of termination of decommissioning of nuclear facilities, it is supposed to confirm the radioactivity concentration obtained by measurement in the site is less than or equal to the concentration corresponding to the criterion. It is needed to estimate the distribution and mean of radioactivity concentration in the evaluation unit using a number of measured data. It is further needed to compare the estimated result with the concentration corresponding to the criterion of site release and to decide if the evaluation unit should comply with the criterion. The estimated result exhibits uncertainty depending on the number of measurement points, which results in a certain probability of the occurrence of decision error according to the uncertainty. It is important to decide the number of measurement points required by revealing a relationship of the error probability to the number of measurement points for site security. We have developed the ESRAD2 (Estimation of Spatial RadioActivity Distribution program version 2), which is an extended version of the existing ESRAD, for estimating the mean of radioactivity concentration and calculating the number of measurement points required according to the error probability. This report describes a method for ensuring compliance with the criterion of site release, structure and functions, input file format, output examples, execution method of ESRAD2, and sample run with ESRAD2.
Hoshino, Yuzuru; Sakamoto, Yoshiaki; Muroi, Masayuki*; Mukai, Satoru*
JAEA-Technology 2015-015, 96 Pages, 2015/07
In order to dispose of the radioactive waste which generates from post-irradiation examination (PIE) facilities, the common evaluation method of radioactivity in wastes from PIE should be established by the actual data such as radioactivity values and the theoretical calculation. In this study, the radioactivity concentrations of 17 nuclides (H-3, C-14, Co-60, Ni-63, Sr-90, Tc-99, Cs-137, Eu-154, U-234, U-235, U-238, Pu-238, Pu-239, Pu-240, Pu-241, Am-241, Cm-244) in combustible wastes stored in NUCLEAR DEVELOPMENT CORPORATION were measured from 3 samples and the radioactivity was calculated by ORIGEN-2 based on initial contents and operation record of the spent fuel. From the comparison of the obtained data by the radiological measurement with the calculated values, the subject to be solved for establishment of the radioactivity evaluation method for PIE was extracted.
Shimada, Taro; Takeda, Seiji; Mukai, Masayuki; Munakata, Masahiro; Tanaka, Tadao
Materials Research Society Symposium Proceedings, Vol.1744, p.229 - 234, 2015/04
Integrated safety assessment methodology which analyzes radionuclide migration reflecting the spatial and temporal changes of disposal systems was developed for a geological disposal site with uplift and denudation, and then some case analyses for an assumed site with sedimentary rocks were carried out. The combination of uniform uplift and denudation has the most effect on the radionuclide migration because the groundwater flow velocity increases with decreasing the depth from the ground surface. In the case without denudation, tilted uplift has more effect than uniform uplift because flow velocity in tilted uplift increase with increasing hydraulic gradient. The long-term change of the geological structures including the uplift and denudation, the hydraulic conditions, and the recharge and outlet of the groundwater around a candidate site should be carefully investigated to determine the appropriate the place,depth and layout of the repository.
Sawaguchi, Takuma; Kadowaki, Mitsushi*; Yamaguchi, Tetsuji; Mukai, Masayuki; Tanaka, Tadao
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 20(2), p.71 - 78, 2013/12
The dissolution rate for montmorillonite under compacted condition was studied in order to evaluate long-term alteration behavior of bentonite buffer materials by highly alkaline groundwater. The dissolution rate of compacted montmorillonite was found to be larger than that of montmorillonite in compacted sand-bentonite mixtures at 130 C, which revealed that the dissolution of montmorillonite was inhibited by decreasing the activity of hydroxide ions () in the compacted mixtures including accessory minerals such as silica. In order to provide reliability for the analysis of bentonite-alteration using a formula of dissolution rate of montmorillonite, it is important to quantify the decrease of in the compacted mixtures and to formulate the dissolution rate of compacted montmorillonite.
Ishigami, Tsutomu; Sukegawa, Takenori*; Mukai, Masayuki
JAEA-Technology 2013-027, 124 Pages, 2013/10
In order to safely and efficiently implement decommissioning of nuclear installations, it is important to beforehand predict decommissioning project management data (PMD) and to develop a decommissioning plan based on the predicted results. The PMD prediction is made with PMD evaluation equations including model parameters such as unit work activity coefficients. Although model parameter values developed so far include uncertainties, little evaluation of the uncertainties and resulted uncertainties in predicted PMD has been made. However information on the uncertainties is valuable in flexibly studying and developing a decommissioning plan. We therefore studied and evaluated uncertainties in model parameters by analyzing the JPDR decommissioning experience data. This report describes an evaluation method of the model parameter uncertainties and their evaluated results.
Yamaguchi, Tetsuji; Kataoka, Masaharu; Sawaguchi, Takuma; Mukai, Masayuki; Hoshino, Seiichi; Tanaka, Tadao; Marsal, F.*; Pellegrini, D.*
Clay Minerals, 48(2), p.185 - 197, 2013/05
Highly alkaline environments induced by cement based materials are likely to deteriorate the physical and/or chemical properties of the bentonite buffer materials in radioactive waste repositories. Predicting long-term alteration of concrete/clay systems requires physico-chemical models and a number of input parameters. In order to provide reliability to the long-term prediction of bentonite buffer performance under disposal conditions, it is necessary to develop and verify reactive transport codes for concrete/clay systems. In this study, a PHREEQC-based, reactive transport analysis code (MC-CEMENT ver.2) was developed and was verified by comparing results of the calculations with observations of the mineralogical evolution at the concrete/argillite interface. The calculation reproduced the observations such as the mineralogical changes limited within one cm in thickness, formation of CaCO and CSH, dissolution of quartz, decrease of porosity in argillite and increase in concrete. These agreements indicate possibility that the models based on lab-scale ( 1 y) experiments can be applied to longer time scale. The fact that the calculation did not reproduce the dissolution of clays and the formation of gypsum indicates that there is still room for improvement in our model.
Ishigami, Tsutomu; Mukai, Masayuki; Sukegawa, Takenori; Matsubara, Takeshi*
JAEA-Data/Code 2012-023, 83 Pages, 2012/11
Verification for site release is one of procedures to confirm termination of decommissioning of nuclear installations. The verification procedure would need to confirm that the radioactive concentration at the site is lower than the criterion value by measurement. Then to efficiently perform the measurement and verification it is one of important issues how to efficiently estimate and evaluate overall spatial radioactivity distribution using a sampling method. For the efficient estimation and evaluation we have applied a Kriging technique which in the geostatistics, and have developed a computer program ESRAD (Estimation of Spatial RadioActivity Distribution). The ESRAD program is designed to support sample selection, calculate a variogram, and estimate a radioactivity distribution for the area concerned. This report describes the Kriging technique, structure and functions of ESRAD, input file format, output examples, execution procedure of ERSAR, and sample run with ESRAD.
Tanaka, Tadao; Mukai, Masayuki
JAEA-Research 2011-053, 41 Pages, 2012/08
To understand the migration phenomenon of radionuclide, actual migration data are experimentally acquired by a batch test, a column test and field trial. In the present study, experimental models about the interactions of radionuclide between the solid phase and the liquid phase were discussed systematically to interpret the migration data acquired by the various techniques and conditions. Equilibrium, reversibility, linearity, mechanism and chemistry in the interactions were considered in discussion of the experimental models. A calculation program, which can analyze migration data obtained under various conditions by applying the selected 9 types of experimental models, was maintained. The calculation program makes it be able to predict the migration behavior of radionuclide under various conditions and to decide the important parameter by a fitting analysis of the migration data.
Nagao, Keisuke*; Okazaki, Ryuji*; Nakamura, Tomoki*; Miura, Yayoi*; Osawa, Takahito; Bajo, Kenichi*; Matsuda, Shintaro*; Ebihara, Mitsuru*; Ireland, T.*; Kitajima, Fumio*; et al.
Science, 333(6046), p.1128 - 1131, 2011/08
A steroid surface materials record regolith processes and a history of cosmic-ray irradiation. Noble gas isotopes in three rocky grains from Itokawa have been determined. High concentrations of solar He, Ne, and Ar, as high as those in lunar soils, are released at variable temperatures from each sample. The isotopic compositions are essentially identical to those of solar wind but distinguishable in He relative abundance. These noble gas characteristics can be explained by repeated implantation and preferential loss of solar He by removal of weathered He-rich rim on the grain surface through friction among regolith grains on Itokawa. Residence time of regolith materials on Itokawa is alculated to be shorter than 10 Myr, suggesting that regolith materials of small asteroids would escape easily to space.
Tanaka, Tadao; Mukai, Masayuki
Humic Substances Research, 5-6(1), p.35 - 43, 2009/00
The present paper describes a theoretical evaluation of the influence of humic-complexation on migration of cationic radionuclides through porous media, where it is assumed that complexation reactions between radionuclides and natural organics, such as humic acid and fulvic acid, can be regarded to follow an instantaneous equilibrium or a first-order kinetic reaction. The calculation results revealed that radionuclide migration in the presence of humic substance was predominantly controlled by relative magnitude of distribution coefficients between the cationic radionuclides and the complexed radionuclides. Radionuclide migration was also affected significantly by the stability of the complexes or the rate constants of the complexation reaction.
Yamasaki, Chisato*; Murakami, Katsuhiko*; Fujii, Yasuyuki*; Sato, Yoshiharu*; Harada, Erimi*; Takeda, Junichi*; Taniya, Takayuki*; Sakate, Ryuichi*; Kikugawa, Shingo*; Shimada, Makoto*; et al.
Nucleic Acids Research, 36(Database), p.D793 - D799, 2008/01
Here we report the new features and improvements in our latest release of the H-Invitational Database, a comprehensive annotation resource for human genes and transcripts. H-InvDB, originally developed as an integrated database of the human transcriptome based on extensive annotation of large sets of fulllength cDNA (FLcDNA) clones, now provides annotation for 120 558 human mRNAs extracted from the International Nucleotide Sequence Databases (INSD), in addition to 54 978 human FLcDNAs, in the latest release H-InvDB. We mapped those human transcripts onto the human genome sequences (NCBI build 36.1) and determined 34 699 human gene clusters, which could define 34 057 protein-coding and 642 non-protein-coding loci; 858 transcribed loci overlapped with predicted pseudogenes.
Yamaguchi, Tetsuji; Yamada, Fumika; Negishi, Kumi*; Hoshino, Seiichi; Mukai, Masayuki; Tanaka, Tadao; Nakayama, Shinichi
Physics and Chemistry of the Earth, 33(Suppl.1), p.S285 - S294, 2008/00
It is important to assess long-term alteration of engineered barrier composed of bentonite and cement for the safety assessment of radioactive waste disposal. In order to promote our development of the assessment methodologies, we developed a secondary mineral formation model for cement based materials and a hydraulic conductivity model for bentonite buffer materials. These models were verified by comparing with experimental observations. We also calculated changes in mineralogy of bentonite buffer materials and accompanying changes in the hydraulic conductivity over 10,000 y. We identified the temperature as an important factor dominating the alteration of the buffer. We also identified that the alteration is limited by slow kinetics of the dissolution of montmorillonite and by the diffusive mass transfer. Our calculation showed that the mineralogical change proceeds rather fast during the initial 1,000 y and slows down afterwards, and that salinity of the groundwater has both positive and negative effects on the hydraulic conductivity.
Tanaka, Tadao; Mukai, Masayuki; Bamba, Tsunetaka
Proceedings of International Symposium on Environmental Modeling and Radioecology, p.275 - 278, 2007/03
Migration behavior of Ce, one of redox-sensitive elements, was studied in natural aquifer loess zone in P.R.China. Migration parameters such as distribution coefficient were obtained by column migration and batch sorption tests. The batch sorption test indicates Ce is irreversibly incorporated near loess surface as Ce(IV). Cerium showed large retardation in migration in the aquifer loess zone. Predicted migratory mobility of Ce in the aquifer, which was calculated by using the distribution coefficient determined by the batch and column tests, could reproduce that in the field test conservatively.
Mukai, Masayuki; Tanaka, Tadao; Yukawa, Kazuhiko; Suryantoro*
Genshiryoku Bakkuendo Kenkyu, 12(1-2), p.41 - 51, 2006/03
To evaluate radionuclides migration through geologic media coexistent with colloids in groundwater, a model has been coded. To evaluate an applicability of four models to colloid transport through porous media, breakthrough curves (BTCs) from column experiments using sand and reddish soil have been analyzed. Instantaneous equilibrium model could not explain both timings of breakthrough and reach to C/C=1 concurrenyly, however 1st order kinetic reaction model successfully simulate them well. BTCs from the reddish soil column have a particular feature that shows step-wise rising pattern in response to alternately inflow of colloid. Both the instantaneous equilibrium, the 1st order kinetic reaction and filtration models could not simulate this feature, however a 1st order kinetic reaction with filtration capacity model reasonably simulates the feature. The model for colloid transport, given an important role as a part of colloidal migration model of radionuclide, has been validated on the basis of the laboratory experiments.
Tanaka, Tadao; Mukai, Masayuki; Nakayama, Shinichi
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10
no abstracts in English
Mukai, Masayuki; Ueda, Masato; Inada, Daisuke; Yukawa, Kazuhiko; Maeda, Toshikatsu; Iida, Yoshihisa
Proceedings of International Symposium NUCEF 2005, p.219 - 224, 2005/08
For better quantitative understanding of radionuclide migration for safety assessment of geologic disposal, JAERI has been conducting experimental and modeling studies on influences of humic substances, highly alkaline conditions and colloids on sorptive and diffusional behavior of TRU in geologic materials. In the absence of fulvic acid, one of humic substances, diffusion of Am through a tuff sample was not detected. By adding fulvic acid, Am was detected in the downstream cell, which indicates the diffusion through the sample. Highly alkaline conditions arisen from cementitious materials may spread by altering chemical and physical properties of geologic materials. Through-diffusion experiments of alkaline species in granite showed that the effective diffusion coefficient of Ca and OH in a cement-equilibrated aqueous solution were found to be higher by almost two orders of magnitude than Na and OH in a NaOH solution. Radionuclide migration can be enhanced by colloids, and thus a calculation code describing the effect of colloids on radionuclide migration has been required.
Tanaka, Tadao; Sakamoto, Yoshiaki; Mukai, Masayuki; Maeda, Toshikatsu; Nakayama, Shinichi
Radiochimica Acta, 92(9-11), p.725 - 729, 2004/12
Migration experiments of Ni for crushed rocks, granite and tuff, were performed under the coexistent condition with a humic acid and a fulvic acid of 0-30 mg/l in concentration, which are Nordic humic substances supplied from International Humic Substance Society. Migration experiments of Ni had been performed by a column system, to investigate migration behavior of Ni through a column packed crushed rock. The Ni concentration in the effluent passed through the column was corresponding to the fractional percentage of Ni complexing with humic substance in influent solution. This result suggests that the Ni complexing with humic substance in influent solution was flowed out from the column without any effective interactions with the rock media. The migration behavior of Ni could be expressed by a migration model taking account of the complexation kinetics of Ni with humic substance in the aqueous phase.
Tanaka, Tadao; Mukai, Masayuki; Li, Z.*; Li, S.*
JAERI-Conf 2003-010, p.142 - 149, 2003/09
An environmental migration test of Sr-85 was carried out in natural unsaturated loess zone at the field test site of China Institute for Radiation Protection, China, and the migratory mobility of Sr was observed during 2 years. As laboratory experiments, the migration experiment of Sr by a column system and the sorption experiment of Sr by a batch system were carried out by using the loess taken from the field test site. We discussed about applicability of sorption data determined from the laboratory experiments to evaluating the Sr migration behavior investigated at the field test site. The Sr migration behavior at the field test site could be expressed by the equilibrium sorption model using distribution coefficients determined from the laboratory experiments. This supports that the valid distribution coefficient for the evaluation of Sr migration in natural environment is predicted from the laboratory experiments.