ABSTRACT
For the calculation of source terms associated with severe accidents, it is necessary to model the release of fission products from fuel as it heats and melts. There is persuasive evidence that these processes, as well as additional chemical and gas phase mass transport processes, are important in the release of fission products from fuel. Nevertheless, it has been found convenient to have simplified fission product release correlations that may not be as definitive as models like FASTGRASS but which attempt in some simple way to capture the essence of the mechanisms. R. A. Lorenz has observed that there is a remarkable consistency in the fission product and structural material release data when reported in terms of a release rate coefficient. If sufficient time-resolved data existed, it would be possible to similarly establish a set of such parameters for each fission product elemental group.
