A PROPOSED MODEL OF BUBBLE GROWTH DURING FAST TRANSIENTS IN THE KEWB REACTOR

Experimental evidence indicates that the dominant shutdown mechanism operating in the KEWB Reactor during short-period transients is void production from radiolytic gas evolution. Growth of bubbles required to produce the observed reactivity changes appears inexplainable on the basis of thermodynamics. Since the dissipation of large amounts of energy occurs in a small volume, a mechanism is proposed for the bubble formation which involves fission fragments. Excellent qualitative correlation is observed between predictions based on the model and experimental observations. (W.D.M.)