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1.2 Conversion

The next step in the chain is conversion of the solid yellowcake, uranium oxide U₃O₈, into a gas, uranium hexafluoride UF₆, also known as hex for short. The reason for this step is that it makes it easier to do enrichment when the uranium is in a gaseous form.
Converting yellowcake (U₃O₈) powder to uranium hexafluoride (UF₆) gas

1.3 Enrichment

Nuclear energy can only be produced when the isotope U-235 is present in a concentration of between 3 to 4%. When uranium is mined, U-235 is only present at a concentration of around 0.7%. So the hex is passed through a number of machines to reduce the concentration of U-238 and to raise the concentration of U-235 isotopes in the mix. This is a very costly, energy-intensive and difficult process to accomplish. We call this link in the chain enrichment because it is enriching the amount of fissile U-235 in the mix. If the users of the same technology enrich the U-235 in the mix to a concentration of 90%, it is possible to make nuclear weapons, as happened in the case of South Africa during apartheid.
Valindaba enrichment facility outside Pretoria (closed during the 1990s)

1.4 Fuel fabrication

The next link in the chain is to take the enriched uranium and make it into nuclear fuel. This involves shaping the uranium into fuel pellets and inserting these into fuel rods. The rods are manufactured of elements such as hafnium (Hf) and zirconium (Zr).
Fuel rods for use in a pressurized water reactor

1.5 The nuclear reactor

Once the fuel has been manufactured it can be transported to and inserted into the nuclear reactor. Nuclear reactors are the technology used to generate power from uranium. There are different types of reactors. Some early reactors such as the Canadian CANDU used raw (unenriched) uranium as its nuclear fuel. More modern reactors rely on enriched uranium. A few ‘fast breeder’ reactors use plutonium for their nuclear fuel.

We also distinguish different reactors by the type of coolant the use. The coolant is the substance used to transfer the heat generated by the nuclear chain reaction into electricity. Some reactors use gas as a coolant, others boiling water, but the majority use pressurized water. The two reactors at the Koeberg power station outside Cape Town are pressurized water reactors (PWRs). Generally, PWRs use two coolant loops because the primary loop takes on some of the short-term radioactivity from the reactor.

The companies that manufacture reactors are few, and orders have slowed down considerably after the Three Mile Island accident in the US in 1979, Chernobyl in the Ukraine in 1986 and Fukushima Daiichi in Japan 2011.

Key global vendors of nuclear reactors in 2013
Company	Nationality
Areva	France
China Guangzhou Nuclear Power Company	China
General Electric-Hitachi	USA-Japan
Korean Electrical Power Co. (KEPCO)	South Korea
Rosatom	Russia
Toshiba-Westinghouse	Japan-USA

1.6 Radioactive waste disposal

The use of a nuclear power station generates radioactive wastes which need to be disposed of so that they do not enter the environment for a considerable time. Dedicated facilities must be created for the disposal of radioactive waste. The wastes generated by the mining of uranium are disposed of in tailings dams. These are generally open air dumps formed from the ore and the liquid wastes generated during the mining and milling. Often radioactive dust is blown into nearby communities and the liquid wastes may contaminate local fresh and underground water supplies.

The wastes from the reactor are generally classified as low-, intermediate- and high- level wastes. The low-level wastes consist of items like tools and work clothing that have been contaminated during use. They are stored in metal drums similar to petrol drums.

Intermediate-level wastes include used filters, steel components from within the reactor and some liquid effluents. They are stored in larger drums filled with a concrete mix. The low- and intermediate-level wastes generated at Koeberg and other nuclear sites in South Africa are transported to the Vaalputs disposal site in Namaqualand.

The high-level wastes mostly consist of the used fuel rods after all the energy has been generated from them. These are stored for initial cooling purposes in ponds on site at the reactors. However, because there is no adequate facility for their safe storage elsewhere in Africa, the spent fuel from the Koeberg plant ahs remained in the on-site ponds. There seems to be no site in preparation for the high-level waste.

Very few sites exist around the world for the long-term deep geological disposal of high-level nuclear waste. In the US, a site was identified at Yucca Mountain, but in 2011 President Obama withdrew financial support and it will no longer be used. The site at Gorleben in Germany, based on a salt mine, has been contested vigorously by protest movements.

Classification of nuclear waste and levels of radioactivity
Type of waste	By volume	By radioactivity
Low-level waste	90%	1%
Intermediate-level waste	7%	4%
High-level waste	3%	95%

Source: World Nuclear Association