Immobilization of the rare earth fraction in lanthanide phosphates LnPO4. Radiation and hydrolytic resistance of the matrix

TL;DR

This study investigates the radiation and hydrolytic stability of a lanthanide phosphate ceramic matrix, demonstrating its resistance to high-dose electron irradiation but noting increased leaching and reduced mechanical strength post-irradiation.

Contribution

It provides new data on the radiation and hydrolytic resistance of monazite-structured lanthanide phosphates, relevant for nuclear waste immobilization.

Findings

Irradiation up to 10^9 Gy does not destroy the phase.

Leaching rate increases by an order of magnitude after irradiation.

Mechanical properties decrease by 32% post-irradiation.

Abstract

Radiation and hydrolytic resistance of Eu0.054Gd0.014Y0.05La0.111Ce0.2515Pr0.094Nd0.3665Sm0.059PO4 with monazite structure has been studied. The powders were obtained by deposition from solutions. Ceramic specimens with relative density ~97% were obtained by Spark Plasma Sintering (heating rate Vh = 50 {\deg}C/min, sintering temperature Ts = 1070 {\deg}C, sintering time ts = 18 min). Irradiation by accelerated electrons up to dose of 10^9 Ge was found not to result in a destruction of the target phase. After the irradiation, an increasing of the leaching rate by an order of magnitude (up to ~10^{-8} g/(cm2*day)) and a reduction of the mechanical properties by 32% as compared to the non-irradiated ceramic specimen were observed.