Criticality studies on molten lead energy amplifiers

Molten lead energy amplifiers present very interesting safety features to e xploit nuclear fission in a subcritical assembly driven by a neutron spalla tion source. To characterize those features, reactivity effects due to geom etric material, and spectral changes are analyzed. A main objective of this study is to find out if reactor subcriticality is kept even in the case of accidents producing large reactor distortions. It is found that this is po ssible in compact fuel arrays that have a high enough operational k(eff) to yield a huge energy amplification, but the negative reactivity safety marg in must be accurately assessed in any subcritical reactor design, as an ess ential point of its safety report. Some hints for future studies and better nuclear data calibration are also identified.