Three types of frozen-seal valves'' were tested for possible use in the MSRE. The seal was melted by direct resistance heat, by induction heat, and by clamp-on Calrod heat. The frozen seal was made in a preformed restriction section of a standard piece of pipe by a cooling-gas jet stream directed at the restriction. All three valves performed satisfactorily through 100 test cycles. The Calrodheated valve was selected for MSRE use on the basis of simplicity of design and of operation. Two of the valves are successfully undergoing further tests on the MSRE Engineering Test Loop. (auth)