Opportunities in Plutonium Metallurgical Research
- PDF / 1,248,384 Bytes
- 12 Pages / 612 x 792 pts (letter) Page_size
- 34 Downloads / 247 Views
0986-OO00-01
Opportunities in Plutonium Metallurgical Research* Adam J. Schwartz Physics and Advanced Technologies Directorate, Lawrence Livermore National Laboratory, L-041, 7000 East Avenue, Livermore, CA, 94550 ABSTRACT This is an exciting time to be involved in plutonium metallurgical research. Over the past few years, there have been significant advances in our understanding of the fundamental materials science of this unusual metal in the areas of self-irradiation induced aging of Pu, the equilibrium phase diagram, the homogenization of δ-phase alloys, and the crystallography and morphology of the α’-phase resulting from the isothermal martensitic phase transformation. In addition, tremendous progress has been made, both experimentally and theoretically, in our understanding of the condensed matter physics and chemistry of the actinides, particularly in the areas of electronic structure and the phonon dispersion curves. Although these communities have made substantial progress, many challenges still remain. This brief overview will address a number of important challenges that we face in fully comprehending the metallurgy of Pu with a specific focus on aging and phase transformations.
INTRODUCTION In 1940, G.T. Seaborg, J.W. Kennedy, and A.C. Wahl created the first man-made Pu at the Cyclotron in Berkeley, California [1]. From this separation-chemistry start to the first 1gram quantity of metal to long after the end of the Manhattan Project, Pu metallurgical research was motivated by the requirement to produce a product. The production of a large quantity of material took precedence over quality, and there was limited extra material or time to conduct detailed basic research. From 1945 onward, the focus began to change. A higher level of effort was placed on determining the basic properties of the actinide metals and alloys with a particular focus on the phase diagrams [2-5]. The driving force and motivation for Pu metallurgical research has undergone a remarkable change in direction over the past two decades. The purpose is no longer to produce a large quantity of material, but rather to understand how plutonium’s properties might change with age [6-12]. The continuous radioactive decay of Pu produces impurity daughter products and lattice damage that accumulate with age. How the damage introduced by radioactive decay and the resulting impurities affect metallurgical aspects of Pu, such as mechanical properties, phase transformations and phase stability, and magnetic properties, are areas of intense research. In spite of these recent research activities, we still do not fully understand the basis of such features as the lattice parameter expansion with time, the volume increase which can be significantly different from that expected from the lattice parameter expansion, the vacancy migration energy, or the mechanism that appears to limit the size of the helium bubbles that form from alpha decay of Pu into U and He. * This article is adapted from “Plutonium Metallurgy: The materials science challenges bridgi
Data Loading...
