Theoretical and experimental investigation of sodium void effect of reactivity

In analysis of the safety of fast reactors under design it is absolutely necessary to consider emergency situations due to partial or complete loss of coolant from the reactor core. For power reactors with a high unit power this problem becomes particularly acute since in this case the loss of sodium from the reactor core may result in a large positive reactivity effect. An emergency situation with escape of coolant is considered both for complete drainage of the reactor and within the framework of a local failure when the coolant escapes from one fuel assembly or molecule. Studies on the dynamics of reactivity variations during local failures are of particular interest since they provide the necessary information for diagnosis of an operating reactor. The methods used to calculate the sodium-void effect of reactivity were verified on uranium critical assemblies.