A New Mechanism for Fission-Product Vaporization in SOURCE IST 2.0

Abstract

The current model for vaporization release, during accidents, of non-noble-gas fission products from the fuel surface in SOURCE 1ST 2.0 was developed for low-volatile fission products. This model can lead to low or delayed calculated releases of volatile fission products. An additional mechanism is proposed to take account of release of volatile elements from the fuel surface as the temperature increases. For each fission-product element, maximum temperatures have been calculated for the existence of any condensed-phase compound. If the limiting temperature is exceeded for a specific fission-product element, release of the remaining fuel-surface inventory of that element can be assumed.