Synroc technology: Perspectives and current status (Review)

Abstract

Dr Eric (Lou) Vance spent 32 years at the Australian Nuclear Science and Technology Organisation (ANSTO), where he was dedicated to the development of Synroc technology, a waste treatment solution for intractable nuclear wastes. The original form of Synroc, a multiphase ceramic wasteform based on stable and leach resistant titanate minerals, was invented by Australian scientists in the late 1970s. This formulation was directed toward the immobilization of PUREX wastes from the reprocessing of nuclear fuels. Synroc at ANSTO under the scientific leadership of Dr Vance since evolved beyond these original titanate ceramics into a waste treatment technology platform. This platform can be applied to produce glass, glass‐ceramic and ceramic wasteforms and offers distinct advantages in terms of waste loading and suppressing volatile losses. The platform therefore provides an opportunity to treat those waste streams that are problematic for glass matrices alone or existing vitrification process technologies. Such wastes include, for example, actinide‐bearing wastes, those that contain large proportions of refractory elements, those with significant fission product or corrosive volatile emissions and those wastes resulting from radiopharmaceutical production. The implementation of the latter will see the industrialization of Synroc technology via a first‐of‐a‐kind Synroc Waste Treatment Facility that is currently under construction at ANSTO. This paper will review Synroc technology, particularly noting the substantial and essential contributions from the late Dr Vance. The review will also provide some perspective on the development of the technology for nuclear waste immobilization and describe the significant recent advancements at ANSTO.

Vitrification of wastes: from unwanted to controlled crystallization, a review

“…Related mineral species are generally considered as "zirconolites" including monoclinic, trigonal, and orthorhombic phases including related minerals like zirkelite [cubic (Ca,Th,Ce)Zr(Ti,Nb) 2 O 7 or (Ti,Ca,Zr)O 2−x ] [Stefanovsky . Zirconolite and the related cubic pyrochlore (see below) have been among the most studied crystalline phases for nuclear waste ceramics, as zirconolite is one of the key phases produced in the multiphase titanatebased ceramic waste form called Synroc [Gregg et al, 2020a, Ringwood et al, 1979b, Vance, 1994, Vance et al, 2017.…”

“…Waste form design generally targets immobilization of Cs and Rb with hollandite, rare earths and actinides with zirconolite and perovskite, Sr with perovskite, and platinoid metals and Tc with an alloy phase [Vance et al, 2014]. Usually some Ti oxide phases like rutile (TiO 2 ) and reduced TiO 2−x phases, Magnéli phases Ti n O 2n−1 , are also present due to interactions with HIP cans or addition of Ti powder to reduce the oxidation state of metals cations [Carter et al, 1996, Gregg et al, 2020a. Other minor titanate phases, which can accommodate large ion fission products, lanthanides, and actinides, are sometimes observed, such as loveringite and related minerals of the crichtonite group such as davidite [Lumpkin and Geisler-Wierwille, 2012].…”

Thermal treatment of Cs-exchanged chabazite by hot isostatic pressing to support decommissioning of Fukushima Daiichi Nuclear Power Plant

“…At present, there are no full-scale HIP plants operational for nuclear waste treatment, however the Australian Nuclear Science and Technology Organisation (ANSTO) are commissioning a HIP plant (Synroc Waste Treatment Plant; SWTF) that is expected to be completed in 2020, with an estimated annual capacity to process ~5000 L of wastes generated from medical isotope production [20]. The UK Nuclear Decommissioning Authority (NDA) have proposed HIPing as a credible option for processing a portion of the civil PuO 2 stockpile [21] (and plutonium-residues) with several research programmes underway.…”

Hot isostatic pressed pyrochlore glass‐ceramics: Revealing structure insides at the reaction interface

“…The high-level wastes generated from the reprocessing of spent nuclear fuels contain minor actinides with long halflives requiring immobilization in a stable solid matrix and isolated from the bio-environment for hundreds of thousands of years. [1][2][3] Apart from the conventional borosilicate glasses, 4,5 various durable crystalline ceramic phases [6][7][8][9][10][11][12][13][14][15][16][17] as well as glass-ceramics (GCs) [18][19][20][21][22][23][24][25][26] have been investigated as potential waste forms for HLWs. More recently, pyrochlore-based GCs as emerging waste forms for immobilizing minor actinides were developed.…”