Structure and leaching characteristics of basaltic glass-ceramics for immobilizing simulated actinides La, Ce and Nd

Basaltic glass‑ceramics were prepared by melting basaltic glass, cooling the melt to the nucleation temperature, followed by a two‑stage nucleation‑crystallization heat‑treatment. Ce, Nd, and La were used to simulate U, Np, and Am in high‑level nuclear waste (HLW), respectively. The structure and leaching characteristics of basaltic glass-ceramics with different contents of simulated Actinides were investigated. The XRD and SEM results indicated the simulated actinides loading reaches 40 wt.%. When the content of simulated actinides exceeded 20 wt.%, the main crystal phase of the basaltic glass-ceramics was oxyapatite. As the content of the simulated actinides increases, the content of oxyapatite crystals increases, which indicates that an increase in the simulated nuclides content actually promotes the formation of basaltic glass-ceramic. The Raman results showed when the amount of simulated actinides exceeds 20 wt.%, the characteristic spectra of oxyapatite crystals appeared in the Raman spectra. The PCT test results showed the normalized mass loss of Na is the greatest, and the normalized leaching rates of rare earth elements are 4 orders of magnitude lower than that of Si and Na.