Leaching Studies of Radionuclides from Solidified Wastes with Theremosetting Resin
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LEACHING STUDIES OF RADIONUCLIDES FROM SOLIDIFIED WASTES WITH THEREMOSETTING RESIN KAZUNORI SUZUKI AND HIROSHI KURIBAYASHI, JGC Corporation, Yokohama, Japan; WATARU MORIMITSU AND ISAMU ONO, Industrial Research Institute of Kanagawa, Yokohama, Japan ABSTRACT This paper reports on studies of the leachability of Co-60 and Cs-137 from simulated LWR radwastes solidified with thermosetting resin and evaluates the effects of chemical fixation on leachability. It is concluded that insolubilization by a nickel-ferrocyanide compound offers an effective chemical fixation of these radionuclides and is a recommended pretreating method for radwastes that are to be solidified. INTRODUCTION In Japan, low- and intermediate-level radioactive wastes generated by commercial nuclear power plants are solidified with cement or asphalt. Solidification processes using thermosetting or thermoplastic resin have recently been developed and are attractive from the standpoints of volume reduction, immobilization of radionuclides and the physical and chemical qualities of the solidified products. JGC Corporation, in collaboration with CEA/ECOPOL(France), has investigated and developed a new solidification process using thermosetting resin, and is planning to install commercial plants based on this process in Japan. Although the disposal of solidified radwaste packages is not yet being practiced in Japan, both ocean dumping and land burial are considered as promising candidates. Radwastes packages stabilized and solidified with chemical ibaterials must possess certain qualities, namely, low leachability, high mechanical strength and thermal stability, during in plant handling, transportation and disposal. In particular, to maintain the safety of the enviroment, minimizing the radionuclide release must be guranteed. This paper reports on studies on the leachability of Co-60 and Cs-137 from simulated LWR wastes solidified with thermosetting resin and evaluates the effectiveness of chemical fixation on leachability. EXPERIMENT The simulated LWR radwastes used in the present experiments were prepared from an anhydrous fine powder of sodium sulfate for BWR and of sodium borate for PWR. Cation and anion ion-exchange resin mixtures(C/A=2/l) with a water content of less than 10% were obtained by drying the spent resin from a boiling water demineralizer. For solidifying the material, a thermosetting resin(a mixture of unsaturated polyester and styrene monomer) was selected. The radionuclides selected in this study were Co-60 and Cs-137, and these nuclides were conditioned and insolubilized by a nickel-ferrocyanide compound, where necessary. Product samples of the wastes solidified with thermosetting resin were prepared by mixing the resin with the simulated radwastes and radionuclides and then adding an initiator and promoter to initiate polymerization.
514 The homogeneous mixture was poured into small cylindrical molding containers (45mm in diameter and 44mm high) and cured. Leaching tests were carried out according to the method recommended
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