Investigation of plutonium allotropic phase transformations through differential scanning calorimetry

The investigation of phase transformations in high purity plutonium metal using a differential scanning calorimetry technique is reported, as a function of both heating and subsequent cooling. Data obtained in this study is compared to previous literature values, showing reasonable agreement for the various measurements. The unique features of this investigation are the very high purity metal used for experimentation, the isolation and analysis of the δ ↔ δ′ transformation, and the reverse transformation behavior of the five solid-solid allotropic transformations upon cooling. It is believed this is the first time complete cooling curves have been published for plutonium phase transformations. The results confirm the slow kinetics of transformations below the δ phase and the unusual martensitic-like behavior of the δ → γ phase change.