Borosilicate Glass-Ceramics Containing Zirconolite and Powellite for RE- and Mo-Rich Nuclear Waste Immobilization

• Published in: Materials Vol. 14; no. 19; p. 5747
• Main Authors: Wan, Wei, Zhu, Yongchang, Zhang, Xingquan, Yang, Debo, Huo, Yonglin, Xu, Chong, Yu, Hongfu, Zhao, Jian, Huo, Jichuan, Meng, Baojian
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.10.2021; MDPI
• Subjects: Borosilicate glass; Ceramics; Cooling; Crystallization; Glass ceramics; Heat; Heat treatment; in situ heat treatment; In situ leaching; Leaching; Microstructure; Molybdenum; multi-phase glass-ceramics; Multiphase; Nuclear energy; Nuclear power plants; Perovskites; powellite; Radioactive wastes; Titanium dioxide; Zirconium dioxide; zirconolite; United Kingdom > UK; United States > US; China
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma14195747

In order to increase the loading of rare earth- and molybdenum-rich high-level waste in the waste forms, zirconolite- and powellite-based multi-phase borosilicate glass-ceramics were synthesized via an in-situ heat treatment method. The effects of the CTZ (CaO, TiO2 and ZrO2) content on the crystallization, microstructure and aqueous durability of the multi-phase borosilicate glass-ceramics were studied. The results indicate that the increase of CTZ content can promote crystallization. The glass-ceramics presented even structures when the CTZ content was ≥ 40 wt%. For the glass-ceramic with 40 wt% CTZ, only zirconolite and powellite crystals were detected and powellite crystals were mainly distributed around zirconolite, whereas for the glass-ceramics with 50 wt% CTZ, perovskite was detected. Furthermore, the leaching rates of Na, Ca, Mo and Nd were in the ×10−3, ×10−4, ×10−3 and ×10−5 g·m−2·d·−1 orders of magnitude on the 28th leaching day, respectively.