Study on Structure and Properties of La2O3-Doped Basaltic Glasses for Immobilizing Simulated Lanthanides.

Qin Tong,Yongchang Zhu,Xingquan Zhang,Zhu Cui,Jichuan Huo

doi:10.3390/ma14164709

Abstract

The La2O3-doped basaltic glass simulated high-level waste form (HLW) was prepared by the solid-state melt method. The simulated waste La2O3 maximum loading and the doping effect on structure, thermal stability, leaching behavior, density, and hardness of basaltic glasses were studied. XRD and SEM results show that the simulated waste loading of La2O3 in basaltic glass can be up to ~46 wt.%, and apatite (CaLa4(SiO4)3O) precipitates when the content of La2O3 reaches 56 wt.%. Raman results indicate that the addition of La2O3 breaks the Si–O–Si bond of large-membered and four-membered, but the number of A13+ involved in the formation of the network increase. Low content of La2O3 can help to repair the glass network, but it destroys the network as above 26 wt.%. DSC results show the thermal stability of simulated waste forms first increases and then decreases with the increase of La2O3 content. With the increase of La2O3 content, the density of the simulated waste form increases, and the hardness decreases. The leaching chemical stability of samples was evaluated by the ASTM Product Consistency Test (PCT) Method, which show that all the samples have good chemical stability. The leaching rates of La and Fe are three orders of magnitude lower than those of the other elements. Among them, L36 has the best comprehensive leaching performance.

Highlights

Published: 20 August 2021The disposal of high-level nuclear wastes (HLW) coming from the reprocessing of spent nuclear fuel is still an international problem, which is characterized by strong radioactivity, long half-life and tremendous harm
High Level Liquid Waste (HLLW) from the reprocessing of spent fuel is rich in dozens of elements [4,5,6], among which lanthanides make up a significant proportion
The La2 O3 -doped basaltic glass simulated waste forms were prepared by the solidstate melt method

Summary

Introduction

The disposal of high-level nuclear wastes (HLW) coming from the reprocessing of spent nuclear fuel is still an international problem, which is characterized by strong radioactivity, long half-life and tremendous harm. High Level Liquid Waste (HLLW) from the reprocessing of spent fuel is rich in dozens of elements [4,5,6], among which lanthanides make up a significant proportion. As a typical representative of lanthanide elements, it is of great significance to study the effect of lanthanum content on the structure and properties of glass. Basalt has existed for more than 100 million years in nature with holocrystalline texture, hypocrystalline texture and glassy texture, which has stable chemical and physical properties and strong weathering resistance [9]. Through the high temperature melting in nature, basalt has a good ability to form glass network [10].

Methods

Results

Conclusion