Experimental and Modeling Review of the Plutonium-Zirconium (Pu-Zr) System: Lost in Translation and Over Time?

Abstract

This article presents a review of the phase equilibria of the Pu-Zr system and discusses the contradictory reports on the experimental phase diagram and misinterpretations that have led to confusion over time. In addition, a review of the few Pu-Zr CALculation of PHAse Diagrams (CALPHAD) assessments is presented with emphasis on the heat of formation of the bcc phase, highlighting a disagreement between CALPHAD and ab initio calculations. Based on the information gathered in this study, a critical re-assessment of the Pu-Zr system involving the f (Pu 28 Zr), h (Pu 4 Zr), kinetically hindered j (PuZr 2 ), and once observed i phases is called for.This article is an invited paper selected from presentations at ''PSDK XIV: Phase Stability and Diffusion Kinetics-Gibbs: Phase Equilibria, Diffusion and Materials Design'' held during MS&T'19, September 29-October 3, 2019, in Portland, Oregon. The special sessions were dedicated to honor Dr. Patrice Turchi, recipient of the ASM International 2019 J. Willard Gibbs Phase Equilibria Award ''for outstanding and pioneering contributions in the application of first-principles, quantum-mechanical calculations to the modeling of phase equilibria and thermodynamic behavior of alloys.'' It has been expanded from its original presentation.