Experimental studies on the partitioning of minor elements between carbonate and aqueous solution were summarized in order to elucidate the partitioning of radioactive elements migrating from high level nuclear waste to geologic environment between carbonate and aqueous solution. The relationships among the partition coefficient, solubility product and solubilitytheoretically derived. The factors causing derivation of the experimental partition coefficients from theoretical ones (diffusion, (were) reaction rate, physical properties of solid solution) were considered. The relationship between the partition coefficients and ionic radii suggests that physical factors of solid solution are important for determining the partition coefficient values.

View full abstract

  In France, reversibility is recommended as an important philosophy for the long lived radioactive waste disposal by the government. ANDRA has been establishing the concept of reversible repository and its step-wise management. Monitoring is considered to play an important role so as to realize the step-wise management. However, it never be allowed that the monitoring system deteriorate the performance of the barrier of the repository. In this report, the concept of the wireless monitoring system, which contributes to monitoring in the reversible repository without any disturbance of the barrier, is presented. Its technical feasibility is also described on the basis of the experimental study.

View full abstract

  A wireless transmission technology uses a low frequency electromagnetic wave (100[Hz] ～ 10[kHz]) as a carrier wave to transmit signals in the deep underground geological condition. However, this electromagnetic wave has not been used so much, because the transmission capacity is less than a high frequency electromagnetic wave, which is used to televisions and cellular phones. On the other hand, the wireless transmission technology that doesn't use the cable is considered to be useful in the radioactive waste disposal repository from the viewpoint of decreasing the influence on the barrier. This paper shows the characteristics of the wirelesstransmission in the granite on the basis of the in situ testing implemented in the Äspö Hard Rock Laboratory of SKB.

View full abstract

  Groundwater was sampled in depth of about 50m for extraction of humic substances in the groundwater. The extraction and concentration of the humic substances were performed with synthetic adsorption resins. The extracted humic substances and reference humic substances were made a comparison in chemical property. Aquatic humic substances from Nordic Lake and non–aquatic Aldrich Co. humic acids were selected for the reference material. The unprocessed groundwater and the humic substances extracted from the groundwater were compared in UV-vis spectra, fluorescence spectra and the concentration ratio of humic acid and fulvic acid which were important in order to know characteristics of humic substances. Humic substances extracted from the groundwater were compared with Nordic humic substances in molecular weight distribution, IR spectra and NMR spectra from a viewpoint of complexation with radionuclides. This resulted that the extracted humic substances showed similar characteristics to humic substances in the groundwater, and that the extracted humic substances had similar characteristics to Nordic humic substances in containing acidic functional group which contributed to complexation and in americium complexation where americium complexed uniformly, independent of the molecular weight distribution as important characteristics for evaluation of effects on migration of radionuclides. These obtained results imply that employed method was applicable to extract dissolved humic substances from groundwater in a non-destructive manner and the dissolved humic substances occurring in groundwater in Japan are similar to aquatic Nordic humic substances, which are available to purchase at IHSS (International Humic Substances Society), in complexation behavior with some kind of metal ions.

View full abstract

  To evaluate colloidal migration of radionuclides through geologic media in groundwater, a calculation code has been developed. Four reaction models, i) instantaneous equilibrium, ii) first order kinetic reaction, iii) filtration, and iv) first order kinetic reaction with filtration capacity, have been discussed on their applicability to colloid transport through porous media on the basis of breakthrough curves from column experiments using sand and reddish soil. The instantaneous equilibrium model could not explain both time course and increase rate of breakthrough curve approaching to C_C/C_Co=1, however the first order kinetic reaction model, as one of models having the property of blocking effect, successfully simulate them. Breakthrough curves from the reddish soil column have a specific behavior showing step-wise pattern of colloid concentration in response to repeated inflow of colloid. The instantaneous equilibrium, the first order kinetic reaction, and the filtration models could not explain this behavior. However the first order kinetic reaction with filtration capacity model reasonably simulates the breakthrough curves with specific behavior. As a basis of colloidal migration model of radionuclides in natural barrier, the colloid transport model has been evaluated its applicability through the laboratory experiments.

View full abstract