Fire testing of fully active medium-level waste forms

The effect of heat on packaged intermediate level waste (ILW) has been studied. This was done in order to be able to predict the behaviour of the ILW under accident conditions involving fire during transport or at the repository. In the study, experimental data were obtained and used in the development and validation of theoretical models to describe aspects of the behaviour of the waste form when subjected to heat. The prime objective was to be able to predict the amounts of radioactive materials released from a given incident. Four ILW streams were selected for experimental study. These four were chosen as the minimum that could be studied to provide a set of data that could be used in the prediction of the behaviour of the majority of ILW produced in the UK. Heating experiments were carried out on a small scale using packaged ILW samples made from active wastes or inactive simulants. Data were obtained on temperatures in the waste form, production of volatile materials, carry-forward of solid particulate materials and carry-forward of radionuclides. The results were used, together with data from full-scale experiments with inactive simulant ILW carried out at Winfrith, to develop and validate a theoretical model. This model calculates the temperature profiles within a package of immobilized ILW as a function of the applied heating conditions. The temperature of the waste form is used to predict the release of radioactive materials from the package. 4 refs., 65 figs., 13 tabs