Tarik A Saleh

Plutonium is a highly unusual metal displaying six allotropic phases between room temperature and 550 Centigrade. The crystal structures present vary from low-density high-symmetry cubic phases to high-density low-symmetry monoclinic phases, presenting unique challenges and opportunities for the researcher. In addition, the properties of plutonium may change over time due to radioactive decay, introducing radiation damage and causing changes in chemistry. Castings of high-density Plutonium were created as part of a research and development effort at Los Alamos National Laboratory. The as-cast material was characterized using a variety of techniques, including resonant ultrasound spectroscopy (RUS), dilatometry, and quasi-static mechanical testing. A brief overview of the experimental technique of RUS as it applies to plutonium will be presented, along with discussion of the elastic moduli of alpha plutonium measured in the newly as-cast state. Compression tests of alpha plutonium and tensile tests of beta and gamma phase plutonium will be presented and compared with previous literature and experiments including older alpha plutonium specimens by previous authors. (C) 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM11

Plutonium is the element with the greatest number of allotropic phases. Thermally induced transformations between these phases are typically characterized by thermal hysteresis and incomplete phase reversion. With Ga substitutional in the lattice, low symmetry phases are replaced by a higher symmetry phase. However, the low temperature martensitic phase transformation (delta ->alpha') in Ga stabilized delta-phase Pu is characterized by a region of thermal hysteresis which can reach 200 degrees C in extent. These regions of thermal hysteresis offer a unique opportunity to study thermodynamics in inhomogeneous systems of coexistent phases. The results of thermophysical properties measured for samples of inhomogeneous unalloyed and Ga alloyed Pu will be discussed and compared with similar measurements of their single phase constituents.