Effect of self-irradiation on the parameters of the α → β transformation of unalloyed plutonium

Damage of the structure of the α phase of plutonium as a result of repeated α ↔ β phase recrystallization and prolonged self-irradiation was estimated based on the changes in the electrical resistance measured at room temperature before and after phase recrystallization. Samples with different time of storage were used. An analysis of the results showed that the electrical resistance of samples grows linearly depending on the number of cycles of phase recrystallization. It has been established that the slope of the dependences obtained is determined by the maximum temperature of the sample in the cycle. At a maximum temperature in the cycle equal to 170°C, an increase in the relative electrical resistance of the samples was ∼2.5%/cycle; when heating to 125°C, ∼0.3%/cycle. The variation of the electrical resistance of the samples stored for ∼20 years depending on the number of cycles of phase recrystallization exhibited a single feature, namely, a decrease in resistance in the first cycle of heating to 170°C rather than an increase observed in the experiments with the samples stored for ∼2.5 year. This decrease is connected with the influence of the possible beginning of migration of radiogenic helium. In the subsequent cycles, the change in the electrical resistance of samples upon prolonged storage was analogous to that of the samples with a short time of storage.