Element 94 on the Periodic Table is Plutonium. (10-12) ???The isotope 233Pu was used in the American Apollo lunar missions to power seismic and other equipment on the lunar surface.??? On page 37 of NASA???s Fiscal Year 2010 -Performance and Accountability report, ???the supply of Plutonium-238 (Pu-238) remains a limiting factor in the exploration of the solar system.