Data on migration analysis for TRU waste repository; Results of the solubility experiments in the presence of organic materials used for cement additives

Suguro, Toshiyasu; Nishikawa, Yoshiaki*; Watahiki, Takashi*; Kagawa, Akio ; Iijima, Kazuki  

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.