With Pu-238 in short supply, it is necessary to investigate other potential fuel sources that may
be suitable for powering radioisotope thermoelectric generators (RTGs). This report has
investigated several candidate isotopes based on their power output, decay products, half-lives,
shielding requirements, availability and ability to be isolated. Through manipulation of the
SCALE modeling program, the feasibility of using transuranic radioisotopes found in spent fuel
was thoroughly examined. In addition to examining the use of single isotopes, the possibility of
selecting an isotope that will decay into another feasible isotope will be explored. This report
attempts to identify isotopes that are suitable alternatives to Pu-238 that both fulfill the power
requirements of deep space missions and stay within the economic constraints associated with
such projects
