Design studies of the Moderated Thermonic Heat Pipe Reactor (MOHTR) concept

Design studies, based primarily on neutronics analysis, have been conducted on a thermionic reactor concept that uses a combined beryllium and zirconium hydride moderator to facilitate the incorporation of heat pipe cooling into compact thermionic fuel element (TFE) based designs useful in the tens of kilowatts electrical power regime. The goal of the design approach is to achieve a single point failure free system with technologies such as TFEs, high-temperature heat pipes, and ZrH moderation, which have extensive test data bases and have been shown to be capable of long lifetimes. Beryllium is used to thermally couple redundant heat pipes to TFEs and ZrH is added to reduce critical size. Neutronic analysis undertaken to investigate this design approach shows that greater reactivity can be achieved for a given geometry with a combination of the two moderator materials than with ZrH alone and that the combined moderator is much less sensitive to hydrogen loss than more traditional ZrH-moderated thermionic reactor designs. These and other analytical approaches have demonstrated the credibility of a heat pipe cooled thermionic reactor concept that has a reactor height and diameter of 60 cm and a reactor mass of 400 kg for 30-kWe power output. 14 refs.,more » 8 figs.« less