Nuclear waste spectrum as evidence of technological extraterrestrial civilizations

The possible observational consequences of galactic civilizations which utilize their local star as a repository for radioactive fissile waste material are considered. If a relatively small fraction of the nuclear resources present in the crust of a terrestrial-type planet were processed via breeder reactors, the resulting stellar spectrum would be selectively modified over geological time periods provided the star has a sufficiently shallow outer convective zone. Consideration of surface convective mixing and stellar lifetimes restricts the possible candidate stars to the approximate spectral range A5-F2. The abundance anomalies resulting from the slow neutron fission of plutonium-239 and uranium-233 are presented and it is argued that these anomalous distributions are unlikely to be duplicated by natural nucleosynthesis processes. Relative to solar system abundances, the elements praseodymium and neodymium are found to be the most overabundant. These elements, along with the radioactive elements technetium and plutonium, could be used to identify A5-F2 candidate stars in a preliminary spectral survey