Evaluation of self-controllability of LMFRs against ATWS

This paper describes a simple and general method to evaluate inherent and passive safety characteristics of fast reactors that uses self-controllability limit lines. The self-controllability limit lines are derived analytically for the extreme conditions such as sodium boiling or fuel melting as linear relationships among the total reactivity, effective coolant and fuel reactivites. The analytically obtained self-controllability limit lines are compared to those obtained by numerical result from the LMFR plant system transient analysis. For a given set of various reactivity coefficients of any actual LMFRs, judgement is made on whether the reactor can maintain the core integrity under ATWS conditions.