Investigations Into the Mobilization of Actinides From ILW Conditioned in Cement and Bitumen and Studies of their Sorptive and Migration Behaviour in Both the Near- and Far-Fields for a Repository Contained in a Deep Salt Environment

Abstract

Experiments have been carried out into the leaching of ILW conditioned in cement and bitumen in concentrated salt solutions. Although difficult to observe with real waste leachates, investigations into the leaching of a simulated waste in cement have indicated leached transuranic levels of ca. 10−9 M ; the amount of activity leached by a quinary salt solution being 102 - 103 times higher . This has been interpreted in terms of a pH effect. For the real waste, spectroscopy has indicated a significantly larger release of Cs from cement than from bitumen. For all waste samples a notable absence of colloidal material was observed ; an observation which can be explained in terms of the high solution ionic strengths and the corresponding influence upon radionuclide solvation.Transuranic mobility studies through salt and sand from a salt dome in Northern Germany have shown the presence of at least two types of species of wildly differing mobility ; one migrating with approximately the same velocity as that of the solvent front and the other strongly retarded. Actinide recoveries (i.e. that passing through the columns) could be strongly influenced by either changing the system pH or by the addition of a competitor such as Ce ; the latter effect pointing to a competitive sorption.

Effects on radionuclide concentrations by cement/ground-water interactions in support of performance assessment of low-level radioactive waste disposal facilities

“…Some studies (e.g., Serne et al 1992, Flambard et al 1985, Nomine and Billon 1989 are available where the leaching of plutonium from cement waste forms has been measured. The results consistently show that plutonium leaches very slowly fiom the cement compared to many other radionuclides.…”

Retention Properties of Pressed Salt for Te, Np, Pu and Am leached from Simulated HLW Glass

“…The initial grain sizes range from 0 to 8 mm and the final dimensions of the columns are L = 8 cm length and S = 7 'cm 2 cross section. The total porosities calculated from = 1 M 6 SLps (ps = 2.16 g I cm 3 , column massA/) are given in Table 1.…”

“…On account of the large backfilled volume even small specific sorption capacities will influence the total release into the flowing ground water considerably. To get an impression on the retention capacity of the backfill material, sorption measurements were carried out using crushed salt [3,4], The present work reports first results of experiments using fully simulated HAW glass and pressed salt as column material.…”