Developments in the leach testing of solidified reactor wastes in the United Kingdom

Abstract

In the United Kingdom, there has been a shift in national waste management strategy towards a policy of routine disposal of appropriate low- and medium-level solid wastes from nuclear power station sites. Traditionally such wastes have been stored in unprocessed forms in special tanks and vaults. The U.K. Central Electricity Generating Board (CEGB) is therefore developing the appropriate plant and technology for conditioning such wastes for disposal, involving solidification. The ability of the solidified waste forms to resist leaching of their contained radionuclides is an important factor in the assessment of their safety and acceptability. One of the first priorities has been to develop a process for solidification of organic and inorganic ion-exchange materials from the Magnox reactors. The conditioning process chosen is to solidify the wastes in a thermosetting organic polymer. This paper describes the experimental study of leaching of specific radionuclides from simulated wastes solidified in a number of different candidate polymers. The paper examines the reasons for carrying out the tests, describes the methods and techniques used and reports the results obtained. Interpretations and observations on the results are provided together with proposals for future work which will form the basis for investigation and understanding of the basic physicochemical parameters involved.