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4 ii. Enrichment
This section looks at:
A. What is enrichment?
After the production of yellowcake – which is currently exported from Australia – the next two steps in the nuclear fuel cycle are:
- Conversion of yellowcake to uranium hexafluoride gas – UF6
- Enrichment, which increases the proportion of the fissile Uranium-235 from 0.7% to 3-5%
The enrichment process is carried out to produce fuel for power reactors or nuclear weapons. It involves partial removal of the non-fissile Uranium-238 in order to increase the proportion of the fissile U-235. It therefore produces two streams of product: enriched uranium and depleted uranium (DU).
At a commercial scale level, there are two methods of enrichment:
- Gaseous diffusion
- Centrifuge
Gaseous diffusion is an obsolescent method of enrichment. No new plants use this method. Gaseous diffusion plants are still in operation in the US and France. Centrifuge technology is used in Russia, the UK and Japan.
Gaseous diffusion
The diffusion process involves forcing uranium hexafluoride gas (UF6) under pressure through a series of porous membranes. As U-235 molecules are lighter than U-238 molecules, they move faster and have a slightly better chance of passing through the pores in the membrane. The UF6 which diffuses through the membrane is thus slightly enriched, while the gas which did not pass through is depleted in U-235. This process is repeated some 1400 times to obtain a product with a concentration of 3 - 5% U-235.
Source: www.uic.com.au/...
Centrifuge
The centrifuge process involves feeding the UF6 gas into a series of cylinders. The cylinders are spun around at supersonic speeds (400 and 500 metres per second). The heavier U-238 concentrates towards the cylinder’s outer edge, and the lighter U-235 concentrates towards the cylinder’s centre. Eventually the two streams of uranium – enriched and depleted – are drawn from the series of cylinders. In the centrifuge process, the number of stages may be only 10 to 20, instead of a thousand or more for diffusion.
Source: www.uic.com.au/...
Both technologies
“Current uranium enrichment methods are expensive, technically difficult and reliant on components engineered to exceedingly high standards. The process consumes vast amounts of energy and requires large infrastructure. These factors have limited the acquisition of enrichment plants and therefore slowed the proliferation of nuclear weapons. It is traditionally assumed that only the most economically and technologically advanced countries could ever develop enrichment capabilities and make it impossible to covertly develop enrichment plants.” Source: sites.greenpeace.org.au/...
B. Australia and Enrichment
Australia has been deeply engaged in enrichment, despite a lack of public awareness of our role. Silex Systems, a private Australian company operating out of the Australian Nuclear Science and Technology Organisation (ANSTO) facility at Lucas Heights, has developed a new method of enrichment using laser technology. On 22 June 2006, Silex Systems announced US government approval for an agreement giving exclusive commercialisation rights to General Electric Company. The Silex-GE agreement will result in commercial deployment of laser enrichment in the US. Download: www.silex.com.au/...pdf
There is one very major problem with laser enrichment: the far greater potential for weapons proliferation. Laser enrichment:
- Is much cheaper than diffusion or centrifuge
- Is much more energy efficient
- Produces considerably fewer greenhouse gas emissions
(See Silex systems submission to the UMPNER inquiry at: http://www.pmc.gov.au/...)
A diffusion or centrifuge plant requires a large industrial complex. Laser technology could be carried out in a small warehouse and go easily undetected. A Greenpeace report on the Silex project at ANSTO quotes a 1981 declassified CIA report on threats posed by laser enrichment of uranium: “Any country might acquire the necessary technology to set up a garage sized plant to produce weapon grade uranium anywhere in the world”. Source: sites.greenpeace.org.au/...
The Greenpeace report documents the development of the Silex project in Australia, including:
- Australian government funding support;
- A special nuclear agreement between Australia and the US to allow the transfer of technology between Silex Systems and the US Enrichment Corporation – the agreement was announced in May 2000 by Minister Downer; and
- Classification of the Silex process as RD – Restricted Data – by the US Secretary of Energy in 2001. The first time in history that privately held technology was given this classification.
According to the UN Secretary General, Kofi Annan, the Nuclear Non-Proliferation Treaty regime faces a twin crisis of compliance and confidence. Now is not the time to be taking actions that result in greater proliferation risk. Read his recent address on this subject at Tokyo University: http://www.un.org/News/Press/docs/2006/sgsm10466.doc.htm
C. Waste
Depleted Uranium (DU) is a toxic heavy metal similar to lead and mercury that accumulates in the ground and waterways and consequently has the potential to enter the food chain. If DU is inhaled or ingested (eg in dust after the explosion of DU munitions), it is a significant health hazard, potentially causing kidney damage and lung cancer.
See: www.who.int/mediacentre/factsheets/...
See: web.ead.anl.gov/uranium/pdf/...
The global DU stockpile is large: at least 1.5 million tonnes globally. Each year another 50,000 tonnes of DU is added. More recently in the US, DU has been used for various industrial purposes including ballast in commercial aircraft and ships (because of its high density) and use in the manufacture of pigments and glazes. The US has also used DU in munitions in the Middle East. However, most DU is stored as waste.
DU in the US had been stored at three Department of Energy (DoE) facilities at Portsmouth, Ohio; Paducah, Kentucky; and Oak Ridge, Tennessee, with the intent of using it. DoE is now rethinking this strategy, after increased controversy about DU contamination. The half life of DU is 4.5 billion years.
See: www.ead.anl.gov/project/...
See: www.hps.org/publicinformation/...l
See: www.ead.anl.gov/project/...
(Glossary – see Uranium-238 (DU) for 4.5 billion year half life)
D. Weapons
Aside from waste, the enrichment process leads to nuclear weapons proliferation. This is because the technology to produce fuel for a nuclear power plant and the technology used to produce fuel for a nuclear weapon is the same. The enrichment process continues until the fuel contains more than 90% of the fissile U-235.
A report by the Australian Strategic Policy Institute released in August 2006 found that the development of the nuclear supply chain in Australia could lead to the proliferation of nuclear weapons in our region.
See: www.aspi.org.au/publications...
Read Max Walsh’s recent article on Australia and nuclear weapons in The Bulletin website: The Nuclear Club
See: www.bulletin.ninemsn.com/bulletin/...
Australia’s domestic debate on enrichment has forced the Federal Government to assure its neighbors, in particular Indonesia, that it is not intending to develop nuclear weapons.
See: www.abc.net.au/news/...
