Over the last decade, several computational methods have been developed and used to examine reactor flow transients caused by pump outage. The variations in system character which have been analyzed are sufficiently diverse that it appears worthwhile to compile them into a single report.

Whenever fissile materials are handled in significant quantities such as in fuel element fabrication, separation processes, or in exponential and/or critical experiments a potential criticality hazard exists. The usual procedure which is followed by those persons conducting critical mass experiments is to either place the potential reactor in a heavily shielded cell or to conduct the experiments remotely in which case distance provides a measure of safety in the event of an unscheduled radiation outburst. In considering potential critically incidents, especially for the personnel not specifically engaged in critical mass studies, it is very likely that at the time of the incident neither the conditions of shielding nor distance will prevail for the personnel involved.