Effect of annealing on the resistivity of self damaged plutonium

When samples of $\alpha$ plutonium are stored at low temperatures their resistivities increase owing to the accumulation of defects produced by the radioactive disintegration of the nuclei. Isochronal annealing experiments have been performed on $\alpha$ plutonium which show that this additional resistivity recovers in two distinct stages centred at ca. 75 and 150 $^\circ$K respectively. In $\delta$ stabilized plutonium the first annealing stage is more pronounced and occurs at lower temperatures, the values of which are dependent on the concentration of aluminium used to stabilize the $\delta$ phase. Isochronal annealing experiments have also been performed on heavily damaged samples of $\alpha$ plutonium and yield further information on the anomalous temperature dependence of the resistivity changes brought about by self irradiation at low temperatures. The correlation between the observed resistivity changes and corresponding changes in the concentration of point defects is discussed.