Effect of dimension of specimen on amounts of cesium-137, strontium-90 and cobalt-60 leached from matrix of hardened cement grout

The relationship between the fraction leached and the ratio of surface area and volume (S/V) of a specimen has been studied in order to evaluate the safety of a cement composite for disposal. The leaching fraction of radionuclides was measured for the different S/V ratios. In a case of either 137Cs, 90Sr or 60Co, the amount leached is directly proportional to the S/V ratio. It is harmony with the empirical formula proposed here, which can be derived from the diffusion equation with a semi-infinite plane source model. The amounts of 137Cs, 90Sr and 60Co leached from a cement composite of 200 l drum size are estimated on the basis of the above relation, referring to the data obtained with a cylindrical shape specimen (4.5 cm in dia. and 4.4 cm high). (auth.)