- A new concept for a fast spectrum Materials Testing Reactor (MTR) is proposed. Its functionality stems from a DOE report outlining performance requirements for a new testing reactor. The utility of various reflectors is analyzed. MgO is shown to be the best reflector; a BeO reflector in particular will cause excessive power peaking and give a lower keffwhen compared to an MgO reflector of the same size. Peak fast flux is >5E15 n/cm2s with a cycle length of one year. The volume of the in-core fast flux irradiation positions is 63,157 cm3.