Included are 88 references on thermionic conversion of heat energy and the use of radioisotopes as power sources. References on thermoelectric conversion are included if the primary energy source is a radioisotope.

Included are 208 unclassified references on nuclear direct energy conversion devices. Major emphasis is placed on auxiliary power devices suitable for use in satellites including reports on nuclear batteries, thermoelectric cells, thermionic conversion, and all phases of the SNAP program, although not all SNAP devices employ direct conversion. This search supersedes a previous search, TID-3540, Isotopic Power and Thermionic Conversion, compiled by Raymond L. Scott in December 1959.