Cladding tube deformation and core emergency cooling in a loss of coolant accident of a pressurized water reactor

The paper summarizes the dominant effects which finally ensure the core coolability of a pressurized water reactor in a loss-of-coolant accident (LOCA). The main results are summarized as follows: The cooling effect of the two-phase mixture which is intensified during reflooding increases temperature differences on the cladding tube circumference and thus limits the mean circumferential burst strains to values of about 50%. An unidirected flow through the fuel rod bundle during the refill and reflooding phases causes maximum cooling channel blockage of about 70%. The coolability of deformed fuel elements can be maintained up to flow blockages of about 90%. All effects investigated indicate that in a LOCA no impairment of core coolability and public safety has to be expected. (orig.)