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Nuclear Power Dossier: Conversion and Enrichment

Jon Hughes

1st June 2006

The secretive side of nuclear power that uses chemicals 10,000 times more potent greenhouse gases than CO2...and is fuelling a nuclear arms race

Milled uranium is commonly called ‘yellowcake’, which describes its characteristic appearance. It still has a long journey to take – both in terms of processes and physically – before it can be used in a reactor. At the milling plant the yellowcake is packed in drums and shipped to a conversion plant. This is a highly risky business, because while yellowcake is the key ingredient for creating nuclear fuel, it is also a key ingredient for making nuclear weapons. It is worth considerably more than its weight in gold on the black market.

Enrichment is a process similar to distilling. Yellowcake contains only about 0.7 per cent uranium-235, the vital ingredient for nuclear fi ssion. In order to bring the concentration of uranium-235 up to the required 3.5 per cent, the oxide is mixed with fluorine and heated to form uranium hexafluoride, a gas commonly known as ‘hex’. While in this gaseous state the lighter molecules of uranium-235 are separated from the heavier uranium-238 by forcing them through a membrane with tiny openings. As it cools the enriched uranium returns to a solid state and is ready for conversion into fuel rods.

The remaining 85 per cent, on cooling, becomes what is known as depleted uranium. It ought then to be placed in sealed containers for final disposal in a geological depository. However, owing to the cost of doing this, and the scarcity of suitable places for it, much of it is held in interim storage: in the United States, during the last 50 years, 500,000 tonnes of depleted uranium have accumulated in cool storage (to stop it becoming gas), designated as ‘temporary’. The UK is estimated to have 30,000 tonnes of depleted uranium stored around the country in 10 tonne casks.

Contamination issues

Enrichment plants are highly toxic environments, using myriad chemical compounds such as fluorine and chlorine alongside other solvents. Around half a tonne of fluorine is used to turn one tonne of uranium into hex.

The global warming potential of fluorine and its halogenated compounds is nearly 10,000 times that of C02. While the nuclear industry keeps no records of such emissions, there can be no doubt that substantial amounts enter the atmosphere. In the US, the government owned US Enrichment Corporation is to pay £7bn over the next 50 years cleaning up after its two enrichment plants. Throughout the 1980s and 1990s both were exposed for releasing radioactive waste and cancer-causing chemicals into the environment.

In Ohio, the soil and underground water around the Piketon plant was found to be extensively contaminated with such cancer-causing chemicals as trichloroethylene, a solvent, and PCBs. It estimated that each day the cooling towers released 30 to 40 pounds of chromium, a toxic and cancer-causing element, into the air.

Another plant in Kentucky has an even worse rap sheet. The Washington Post reported that between between 1952 and 1987, 61,000 pounds of radioactive uranium flowed out of the Paducah plant and into the Ohio River. In 1988, aquifers near the plant were found to be contaminated with technetium and chemical carcinogens, which prompted a multimillion-dollar clean-up operation led by the US Environmental Protection Agency (EPA).

When it has left the enrichment plant, the uranium has to go through further chemical processes at a fabrication plant. This is where it is converted into ceramic pellets of uranium dioxide and packed in zirconium alloy tubes to make fuel rods, which are finally bundled together to form fuel assemblies for reactors. Zirconium alloy is another mineral that has to be mined and purified for use in the fuel fabrication process.

This is yet another heavy duty chemical process for which the nuclear industry doesn’t keep figures on emissions. However, all such plants rely heavily on air and water filters to stop such deadly emissions reaching the environment. When environmental tests were conducted round a fabrication plant outside St Louis in America, the monitoring well was found to be contaminated with radioactive technetium-99, a radioactive and potentially carcinogenic by-product of nuclear fission known to enter the thyroid gland and intestines.

Piracy risks

Mines and mills use their remoteness as security, but this could also hide a multitude of sins. We only know how much ore has been milled from the mine records. In politically unstable, impoverished countries, such as the former Soviet Union, where weapons grade plutonium has found its way onto the black market, there is clearly a potential for milled uranium to be diverted or hijacked en route to the enrichment plant.

All the processes required to prepare the fuel for a nuclear power station don’t occur in the same location. The Australian uranium industry describes a typical journey for yellowcake destined for Belgium: first it is shipped to the US for conversion to uranium hexafluoride; the ‘hex’ is then sent from the US to Russia for enrichment, then on to a fuel fabrication plant in Germany to be turned into uranium dioxide, before going into the core of a reactor in Belgium. The opportunity for piracy is all too apparent. It is a problem the International Atomic Energy Agency is aware of, but is finding increasingly difficult to police as the number of enrichment plants in the world increases.

In 1983, the prestigious Stockholm International Peace Research Institute (SIPRI) called for a worldwide ban on centrifuge enrichment technology because of its potential for nuclear proliferation. In its book Uranium Enrichment and Nuclear Weapon Proliferation, SIPRI said that existing centrifuge facilities ‘should be shut down and dismantled’. If that were impossible, then SIPRI recommended that the facilities be ‘internationalised’ and ‘managed in such a way as to prevent the further dissemination of this process… the objective should be to phase out the gas centrifuge technique for uranium enrichment.’

SIPRI’s recommendation fell on deaf ears. At that time only three commercial scale centrifuge enrichments plants existed, all owned by the European consortium Urenco. Now the technology has spread to at least 10 countries, most of which obtained the technology either directly or indirectly from Urenco.

The first nation to do so was Pakistan, after Abdul Qadeer Khan famously stole centrifuge blueprints from Urenco and used them as the basis for Pakistan’s successful programme to develop and produce nuclear weapons. The respected Nuclear Information and Research Service says these blueprints were then made available for sale. Only this year, not only Iran but also Brazil became countries with enrichment capabilites. An American consortium is currently building such a plant in New Mexico, at a cost of $1.4 billion. The problem is that price or expertise is proving no barrier to any state determined to have an enrichment plant.

‘We just cannot continue business as usual, in that every country can build its own factories for separating plutonium or enriching uranium,’ Mohamed El Baradei, head of the International Atomic Energy Agency warned late last year.

‘Then we are really talking about 30, 40 countries sitting on the fence with a nuclear weapons capability that could be converted into a nuclear weapon in a matter of months.’

To read the full Nuclear Power Dossier click here

This article first appeared in the Ecologist June 2006

 

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