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Suguro, Toshiyasu; Nishikawa, Yoshiaki*; Watahiki, Takashi*; Kagawa, Akio
JAEA-Technology 2013-023, 22 Pages, 2013/10
For safety assessment of TRU waste disposal, solubility of plutonium was investigated under hardened cement paste porewater condition. Polycarboxylic acid compound, which have the possibility to be used for the TRU waste disposal, was selected as the cement admixture for the experiment. Initial concentration of Pu was 10 M in the experiment. The porewater of hardened cement paste was obtained by squeezing out the kneading of ordinary portland cement and deionized water with the cement admixture. The porewater of hardened cement paste without cement admixture is also used for the experiment. The maximum experimental period was 154 days. The experiment was carried out at room temperature (298 5 K) under argon atmosphere, in which oxygen concentration was lower than 1 ppm. Pu concentration in the porewater of hardened cement paste with or without the cement admixture were in the order of 10 mol/dm after 154 days. This value is comparable to the solubility of Pu(IV) under high pH condition, suggesting that the solubility of Pu was not affected by the cement admixture in hardened cement paste.
Suguro, Toshiyasu; Nishikawa, Yoshiaki*; Watahiki, Takashi*; Kagawa, Akio; Iijima, Kazuki
JAEA-Technology 2010-048, 32 Pages, 2011/03
Cementitious materials are considered to be necessary for the construction of TRU waste repository. The cement additives are used for cements and concretes in order to provide their fluidity. Many kinds of cement additives contain organic compounds which may increase radionuclide solubility by complex formation. Therefore, it is important to obtain the solubility data with cement additives for safety assessment of TRU waste disposal. In this work, two types of cement additives, such as sodium formaldehyde acid polymer and poly carboxylic acid polymer which are expected to be applied to the TRU waste disposal system, are selected. Since the chemical condition of the repository is considered to be reducing, the authors carried out batch-type experiments of plutonium solubility under reducing (NaSO added as reducant) and anoxic condition ([O] 1 ppm). Other experimental conditions are (1)initial plutonium concentration; 10 M, (2) temperature; 2985 K, (3)experimental period; 7, 14, 28 and 56 days and (4) molecular weight of cement additives; without fractionation 5,000 and 5,000. The plutonium concentration in the absence of the cement additives was in the order of 10 mol dm, while, those in the presence of cement additives were two or three orders of magnitude higher. Additionally, low molecular weight fraction of cement additives brought relatively higher plutonium concentration than high molecular weight fraction.
Suguro, Toshiyasu; Nishikawa, Yoshiaki*; Komuro, Takashi*; Kagawa, Akio; Kashiwazaki, Hiroshi; Yamada, Kazuo
JAEA-Technology 2007-058, 20 Pages, 2007/11
For safety assessment of TRU waste disposal, data on sorption data of plutonium on Tuff have been obtained by a static batch-type experiment. Because the repository condition will be reducing and be affected by considerable amount of nitrate in waste, the authors carried out the experiments using Tuff under the reducing (NaSO as added as reductant) and anoxic condition (O1 ppm) and solution of 0 to 0.5 M NaNO. The experimental results suggest that distribution coefficient (Kd) ranges 0.2 to 0.7 m kg in case of L/S=0.1 m kg. Similarly the Kd ranges, 1 to 7 m kg at L/S=1 m kg. However, almost samples of the solution after experiments were plutonium solubility less than detection limit(10mol/dm) of alpha spectrometer. The reason, it is guessed plutonium coprecipitation with calcium hydroxide, because experiments using saturated calcium hydroxide in the liquid.
; Nishikawa, Yoshiaki*; Kagawa, Akio
JNC TN8410 2002-009, 191 Pages, 2002/11
Organic TRU waste form (organic matrix and/or organic matter in waste) seems to be decomposed in the repository in long term by the reaction with water, radiation and by effect of microorganisms. Groundwater intruded into the repository dissolves soluble organic components as degradation products from the waste form. It is possible that complexation of transuranic elements with soluble organic component makes solubility higher and makes sorption coefficient of days and rocks lower. These phenomena may affect the performance assessment of the TRU waste repository. This paper reports the chemical degradation of asphalt as a material of organic TRU waste form by contacting water under reducing condition. The chemical degradation tests by contacting water in reducing condition were conducted in (1)asphalt +water +iron powder system (AH) (2)asphalt +calcium hydroxide +sodium nitrate water +ion powder system (ACNH) (3)asphalt +sodium hydroxide +water +iron powder system (AOH). The test result of TOC of leachant shows TOC does not increase by time in AH and ACNH case, but TOC of leachant increases in AOH case. In previous research, TOC in high alkaline (10M-NaOH) system in aerobic condition showed high value. Chemical degradation mechanism of asphalt seems to be mainly oxidative decomposition, but even under reducing condition it is possible that soluble organic components are formed by alkaline hydrolysis.
Fukumoto, Masahiro; Nishikawa, Yoshiaki*; Kagawa, Akio; Kawamura, Kazuhiro
JNC TN8400 2001-002, 23 Pages, 2000/12
The soluble organic compounds generated by radiological degradation of asphalt ( ray) were confirmed as a part of influence of the bituminized waste degradation in the TRU waste repository. Especially, the influence of the nitrate was focused on. As a result, the concentration of the soluble organic compounds generated by radiological degradation of asphalt (10MGy, ray which is correspond to absorbed dose of asphalt for 1,000,000 years) were lower (each formic acid : about 50mg/dm, acetic acid : about 30mg/dm and oxalic acid : about 2mg/dm) than that of the formic acid, the acetic acid and the oxalic acid which Valcke et al. had shown (the influence of the organic at the solubility examination which uses Pu and Am). Moreover, the change in the concentration of TOC and the soluble organic compounds (formic acid, acetic acid and oxalic acid) is little under the existence of nitrate ion. That is, the formic acid and acetic acid which can be organic ligands were generated little by oxidative decomposition of asphalt in the process that nitrate ion becomes nitrite ion by radiation. The influence of the soluble organic compounds by the radiological degradation of the asphalt ( ray) on adsorption and solubility by the complexation of radionuclides in the performance assessment can be limited.
Kagawa, Akio; Kawamura, Kazuhiro;
Journal of Nuclear Science and Technology, 37(10), p.934 - 937, 2000/10
None
; Nishikawa, Yoshiaki*; Kagawa, Akio;
JNC TN8400 2000-017, 30 Pages, 2000/03
The influence of the cement additives on the distribution coefficients of americium-241 to the Ca-bentonite was confirmed. The adsorption experiment of americium-241 to Ca-bentonite with cement additives was performed by the batch method, as a part of the influence evaluation of the organic in the research of TRU waste disposal. As a result, the distribution coefficient of americium-241 to the Ca-bentonite was over 1.2E+3m/kg in the condition of the absence of cement additives. In the case of low concentration (0.3g/kg) of the naphthalenesulfonic acid type cement additives, the distribution coefficient was 5.2E+2mkg. And, in the case of high concentration (30g/kg) of the same cement additives, the distribution coefficients was 2.0E-1m/kg. On the other hand in the case of flow concentration (0.5g/kg) of the polycarboxylic acid type cement additives, the distribution coefficients was over 1.3E+3m/kg. And, in the case of high concentration (50g/kg) of the same cement additives, the distribution coefficient was 1.8E-1m/kg. Here, selected cement additives concentrations were based on a standard concentration of 10g/kg when the ratio of water:cement is about one. From these results, the distribution coefficient of americium-241 to the Ca-bentonite decreases according cement additive concentration. The distribution coefficients were similar on different kinds of cement additives. The cement additives concentration influences the distribution coefficient. The distribution coefficient was small in the case of high concentration of the cement additives. That is, it is thought that the cement additives have small influences on the distribution coefficient of americium-241 to the Ca-bentonite in the case of low concentration, though the cement additives have influences on the distribution coefficient of americium-241 to the Ca-bentonite in the case of high concentration.
Kagawa, Akio; Suguro, Toshiyasu; Fukumoto, Masahiro; Miyamoto, Yoichi; Nakahishi, Yoshio
PNC TN8410 95-202, 108 Pages, 1995/06
None
Kagawa, Akio; Suguro, Toshiyasu; Fukumoto, Masahiro; Miyamoto, Yoichi; Nakahishi, Yoshio
PNC TN8410 94-281, 60 Pages, 1994/08
None
*; Ouchi, Jin; *; *; *; Kagawa, Akio; ; *
PNC TN8410 88-045, 85 Pages, 1988/09
None
*; *; Kagawa, Akio; ; *; Ouchi, Jin; *; *
PNC TN8410 88-044, 75 Pages, 1988/09
None
*; Kagawa, Akio; Miyo, Hiroaki*; *; *; *; *; *
PNC TN841 84-17, 79 Pages, 1984/03
no abstracts in English
*; Miyo, Hiroaki*; *; *; Maeda, Katsuo; *; *; Kagawa, Akio
PNC TN841 83-50, 28 Pages, 1983/07
no abstracts in English