Investigation of safety of micro modular reactors for mobile applications

Abstract Micro Modular Reactors are innovative nuclear reactors with small power, in fact a sub-group of SMR. Given their small power level, several MMR designs are transportable, which make them attractive for mini- or microgrids in remote, sparsely populated areas, remote mining operations, marine propulsion, disaster relief or even in space, e.g. on the Moon, on Mars or for powering a space propulsion system. A special class of MMRs are heat pipe cooled MMRs (HP-MMR). The advantage of using heat pipes is that they are a very reliable, passively operating device that transports heat from the reactor core to the power conversion unit without active components. In addition, they provide redundancy by number, which means that if one of several heat pipes fails, the other ones will take over the additional heat transport. Such a redundancy is preferred when easy access to the heat pipe or to the reactor is not feasible. There are already designs of HP-MMRs. One of them is the 5 MW special purpose reactor (SPR) designed by Los Alamos National Laboratory (LANL), improved by Idaho National Laboratory (INL). This reactor was selected as a reference design to carry out a safety analysis using the German thermal hydraulic system code AC 2 /ATHLET developed by GRS. The work is carried out within the project MISHA, funded by the German Ministry of Research, Technology and Space (BMFTR).