FACTORS INFLUENCING THE DIFFUSION OF URANIUM, PLUTONIUM AND RADIUM THROUGH SHERWOOD SANDSTONE FROM SELLAFIELD, CUMBRIA

As part of the Nirex Safety Assessment Research Programme, factors inf luencing the diffusion and sorption of radioelements are being investi gated. Through-diffusion experiments have been carried out to study th e diffusion of (i) uranium and plutonium in the presence and absence o f cellulosic degradation products, and (ii) radium under conditions of different ionic strength solutions and at two initial radium concentr ations. Geological samples used were from the Sherwood Sandstone group , Sellafield, Cumbria. The diffusion of uranium and plutonium was infl uenced by the presence of organic materials. The effect was less prono unced in the case of uranium because uranium sorption was low in all c ases, whereas plutonium sorption was low only when organic materials w ere present. The radium through-diffusion experiments gave results ind icative of competitive ion effects. The high ionic-strength groundwate r experiments gave values for sorption less than half those measured f or the lower ionic strength case. In the experiments with lower initia l radium concentration, sorption was observed to be higher.