The Thermionic System Evaluation Test (TSET) facility, part of the TOPAZ International Program, in Albuquerque, New Mexico is currently testing Russian TOPAZ II space power systems (Wold 1993). The TOPAZ International Program has received six TOPAZ II Space Nuclear power Reactors. Two of these reactors (Eh‐43 and Eh‐44) are considered ‘‘flight quality.’’ A considerable transfer of technology has occurred during the preparations for acceptance testing of the Eh‐43 and Eh‐44 TOPAZ II reactors. The Eh‐43 and Eh‐44 are new systems that have not undergone any testing and require the coolant loop and gas cavities to be filled. The new systems will undergo an acceptance process that ranges from receipt inspection to thermal vacuum testing. The knowledge we gain from these tests will help determine the use of this technology in future applications. © 1995American Institute of Physics