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.
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[edit] Manufacture
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 1150–1200 °C (2102–2192 °F).
The result is a cylinder of hard, dense, black synthetic rock.
[edit] Comparisons
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.
Different types of Synroc waste forms (ratios of component minerals, specific HIP pressures and temperatures etc.) can be developed for the immobilisation of different types of waste.
Synroc is not a disposal method. Synroc still has to be stored, often underground. Even though the waste is held in a solid lattice and prevented from spreading, it is still radioactive and can have a negative effect on its surroundings. Synroc is a superior method of nuclear waste storage because it minimises leaching.
[edit] Production Use
In January 2010, the United States Department of Energy selected Hot Isostatic Pressing (HIP) for processing waste at the Idaho National Laboratory. [1]
In April 2008, the Batelle Energy Alliance signed a contract with ANSTO to demonstrate the benefits of Synroc in processing waste managed by Batelle as part of its contract to manage the Idaho National Laboratory. [2]
Synroc was chosen in April 2005 for a multi-million dollar "demonstration" contract to eliminate 5 t (5.5 short tons) of plutonium-contaminated waste at British Nuclear Fuel's Sellafield plant, on the northwest coast of England.
[edit] References
- ^ US Department of Energy (January 4, 2010), Federal Register (excerpt), Vol. 75/1, pp. 137–140, http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=2010_register&docid=fr04ja10-38.pdf, retrieved May 5, 2010
- ^ "ANSTO Inc HIP demonstration contract award" (Press release). ANSTO. April 1, 2008. http://www.synrocansto.com/Download/files/Idaho_release_Mar08.pdf. Retrieved May 5, 2010.
