The seemingly insurmountable problems experienced in most industrialised countries about the disposal of high-level radioactive waste were thrown into the local spotlight recently when the Cape Town city council cited them as a reason for its intention to refuse land development rights for the proposed pebble bed nuclear reactor.
The government is pondering the wisdom of plans by power utility Eskom, the Industrial Development Corporation and British Nuclear Fuels to establish a pilot R3.5 billion pebble bed reactor at Koeberg.
Like all nuclear projects, the pebble bed reactor has faced an uphill battle against environmental groups, even though the developers claim to be confident the reactor has the potential to rake in billions of rands in exports.
A government decision on the project is believed to be weeks away, but the Cape Town city council has already thrown down its gauntlet.
According to the city, the pebble bed reactor's environmental impact report does not address adequately the fate of 800 tons of high-level nuclear waste that is expected to accumulate at Koeberg over the reactor's 40-year lifetime.
Spent fuel, like all radioactive materials, continues to generate heat long after it is lifted out of the reactor. The rate of heat emission must be allowed to diminish for several decades (50 years is often mentioned) before the waste fuel can be placed in rock for ultimate disposal. The waste then remains radioactive, slowly cooling off for thousands of years.
In a sense, the city council has hit the soft underbelly of the pebble bed reactor project. Nuclear waste is an emotive and politically sensitive subject. This is to a large extent why the government has taken three years to prepare another draft policy document on the matter, after the first draft was released in November 2000.
The new draft policy compiled by the department of minerals and energy has not yet been made public. It is being perused by the departments of health, environmental affairs and tourism, and water affairs and forestry. Those in the know reckon it will probably see the light of day before the end of June.
The storage of nuclear waste is authorised by the national nuclear regulator. High-level waste from Koeberg is stored on site, and low and intermediate nuclear waste is stored underground at Vaalputs in the northern Cape.
The pebble bed reactor is expected to generate 19 tons, or 270 000 spent fuel pebbles a year, of which less than 1 ton is depleted uranium. The spent fuel is much easier to store than fuel rods from conventional nuclear reactors because the silicon carbide coating on the fuel particles keeps the radioactive decay particles isolated.
The developers believe the pebble bed reactor can handle nuclear waste efficiently and safely. Spent fuel will be stored in dry storage tanks and no spent fuel will be removed from the reactor site.
After 40 years, if the reactor is shut down, the spent fuel can be stored on site for another 40 years before being sent to a final repository. And herein lies the crunch.
Around the world, governments are wrestling with only four known final solutions for the disposal of high-level nuclear waste: deep holes in the ground, reprocessing and recycling, transmutation and long-term extended storage.
At present most nuclear reactors store their own waste.
The options in the local context are far narrower. Transmutation of high-level nuclear waste is not an option here because the processes are still a long way off in terms of research and development.
The reprocessing of nuclear waste is also hardly an option because of international constraints on the production of plutonium and because the reactor pebbles cannot be reprocessed.
The second option, storage of high-level nuclear waste on site, is safe. But some countries view it as a security and environmental hazard, while there is a perception among the public that nuclear agencies keep spent nuclear fuel on site because they do not know what else to do with it.
Internationally, nuclear authorities recognise that it is safe to keep spent nuclear fuel on site, but eventually the waste will have to go somewhere, most likely deep underground.
Although such a solution is technically feasible, the probability of such a site being established still seems some way off.
An example of this approach to the disposal of nuclear waste can be seen in the US, where the Nuclear Regulation Commission's waste confidence rule, adopted in the 1980s, states: "If necessary, spent fuel generated in any reactor can be stored safely and without significant environmental impacts for at least 30 years beyond the licensed life of that reactor at its spent storage basin, or at either onsite or offsite independent spent fuel storage installations."
The commission "believes there is reasonable assurance that at least one mined geological repository will be available within the first quarter of the 21st century and sufficient repository capacity will be available within 30 years beyond the licensed life for the operation of any reactor to dispose of the high-level waste".
US President George W Bush recently authorised the use of the Yucca Mountain site in Nevada as a final repository, but the decision still has to be ratified by congress.
The proposal to dump 77 000 tons of spent fuel in casks at the Yucca site took 24 years to plan and $4 billion in studies.
The Finnish parliament recently ratified a decision to construct a spent nuclear fuel storage facility at Olkiluoto. Research and development for this site took 20 years and the application for government approval was the subject of wide public scrutiny. The site is expected to start operating in 2020.
How will these underground sites work? According to the local branch of the Institution of Nuclear Engineers, potentially suitable rock formations (between 500m and 1km underground) are under investigation in several countries. The ideal rock formation is an essentially unfractured rock body not subject to groundwater flow.
The nuclear waste may be packaged in massive steel containers, such as have been proposed in Switzerland, or 6cm copper containers, which Sweden believes will insulate the nuclear material for a million years. Other materials such as titanium are also mentioned.
The containers are placed in pigeon holes and packed with a material such as bentonite clay, which swells on contact with water. Water is thus excluded and the corrosion of the containers is delayed. When the repository is full, the tunnels and shafts are filled, possibly with a mixture of sand and bentonite, and plugged with concrete.
The nuclear industry argues that delaying the decision to build a final waste disposal site gives it time to improve the technology involved - although there is acknowledgement that this presents a picture to the public that the industry does not know what to do with its waste.
Some argue that the reason the US has been tardy in commissioning disposal facilities is simply that there is no urgent technical need for a disposal site.
What has been clearly established in local environmental legislation, however, is the principle that the generator of the waste must pay for its disposal.
The government is not in favour of allowing power utilities to operate their own nuclear waste programmes because it fears the companies might cut corners on costs and compromise safety.
However, it has not yet been determined whether the private sector will be allowed to operate low or intermediate nuclear waste sites like Vaalputs.
It seems South Africa won't need to take a decision on a final nuclear repository until 2030. It may even be possible by then to sell the waste to another country.