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

Wei Wan,Baojian Meng,Yongchang Zhu,Chong Xu,Hongfu Yu,Debo Yang,Jichuan Huo,Jian Zhao,Xingquan Zhang,Yonglin Huo

doi:10.3390/ma14195747

Wei Wan, Baojian Meng + Show 8 more

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https://doi.org/10.3390/ma14195747

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Abstract

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.

Highlights

Nuclear energy as a net-zero carbon emission energy source brings convenience to industry and life, but a large amount of spent fuel is produced in the process of producing nuclear energy
All of the above have two exothermic peaks at around 776 ◦C and 941 ◦C, which corresponds to the crystallization of zirconolite [17] and powellite phase, respectively, and the peak at 776 ◦C strengthened with the increasing content of CTZ
The multi-phase borosilicate glass-ceramics containing zirconolite and powellite with different CTZ content were synthesized for rare earths (RE)- and Mo-rich high-level waste (HLW) immobilization by in situ thermal treatment

Summary

Introduction

Nuclear energy as a net-zero carbon emission energy source brings convenience to industry and life, but a large amount of spent fuel is produced in the process of producing nuclear energy. Some countries, including the US, Canada and Sweden, have decided to leave their spent fuel in interim storage, whereas other countries such as France, Russia, the UK and Japan reprocess their spent nuclear fuel in order to recycle U and Pu that is used in new nuclear fuel and to reduce the radiotoxicity of the ultimate waste [1,2,3]. There are many radionuclides in HLW, which have strong radiotoxicity and can cause heritable damage to the organism. Once these radionuclides spill, they will have a devastating impact on the biosphere. How to immobilize HLW safely is a hot topic for researchers

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