First-Principles Study of Thermo-Physical Properties of Pu-Containing Gd₂Zr₂O₇.

Pengcheng Li,Sa Zhang,Hengfeng Gong,Fengai Zhao,Zijiang Liu,Xiaotao Zu,Haiyan Xiao,Haibin Zhang

doi:10.3390/nano9020196

Abstract

A density functional theory plus Hubbard U method is used to investigate how the incorporation of Pu waste into Gd2Zr2O7 pyrochlore influences its thermo-physical properties. It is found that immobilization of Pu at Gd-site of Gd2Zr2O7 has minor effects on the mechanical and thermal properties, whereas substitution of Pu for Zr-site results in remarkable influences on the structural parameters, elastic moduli, elastic isotropy, Debye temperature and electronic structure. The discrepancy in thermo-physical properties between Gd2−yPuyZr2O7 and Gd2Zr2−yPuyO7 may be a result of their different structural and electronic structures. This study provides a direct insight into the thermo-physical properties of Pu-containing Gd2Zr2O7, which will be important for further investigation of nuclear waste immobilization by pyrochlores.

Highlights

As the nuclear industry develops fast, ways to treat spent fuel and nuclear waste safely, such as plutonium and minor actinides (Np, Am, Cm), has become an important environmental conservation issue [1,2,3]
One method proposed for the treatment of plutonium is immobilization in zirconate pyrochlores, Gd2Zr2O7, which has high thermal stability, high chemical durability, and high radiation tolerance [6,7,8,9]
Zhao et al synthesized (Gd1−xCex)2Zr2O7+x (0 ≤ x ≤ 0.6) solid solutions, indicating that Ce3+ ions can be incorporated into the Gd3+ sites

Summary

Introduction

As the nuclear industry develops fast, ways to treat spent fuel and nuclear waste safely, such as plutonium and minor actinides (Np, Am, Cm), has become an important environmental conservation issue [1,2,3]. Zhao et al synthesized (Gd1−xCex)2Zr2O7+x (0 ≤ x ≤ 0.6) solid solutions, indicating that Ce3+ ions can be incorporated into the Gd3+ sites. Similar solution behavior and structural properties for Pu incorporation in Gd2Zr2O7 have been obtained by first-principles calculations [15,16,17].

Results

Conclusion