Synroc

Synroc, a portmanteau of "synthetic rock", is a means of safely storing radioactive waste. It was pioneered in 1978 by a team led by Dr Ted Ringwood at the Australian National University, with further research undertaken in collaboration with ANSTO at research laboratories in Lucas Heights.

Synroc is composed of three titanate minerals – hollandite, zirconolite and perovskite – plus rutile and a small amount of metal alloy. These are combined into a slurry to which is added a portion of high-level liquid nuclear waste. The mixture is dried and calcined at 750 °C (1,380 °F) to produce a powder.

The powder is then compressed in a process known as Hot Isostatic Pressing (HIP), where it is compressed within a bellows-like stainless steel container at temperatures of 1,150–1,200 °C (2,100–2,190 °F).

The result is a cylinder of hard, dense, black synthetic rock.

If stored in a liquid form, nuclear waste can enter the environment and the waterways, and cause widespread damage. As a solid, these risks are greatly minimised.

Unlike borosilicate glass, which is amorphous, Synroc is a ceramic that incorporates the radioactive waste into its crystal structure. Naturally occurring rocks can store radioactive materials for long periods. The aim of Synroc is to imitate this by converting liquid into a crystalline structure and use to store radioactive waste. Synroc-based glass composite materials (GCM) combine the process and chemical flexibility of glass with the superior chemical durability of ceramics and can achieve higher waste loadings.

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