Heat and dust cast a pall over ground zero: Thirty years after nuclear testing laid waste to Maralinga in central Australia, doubts remain over plans for a clean-up, says Gren Manuel

PHOTOGRAPHS of the former British nuclear test site at Maralinga in central Australia usually show a barren desert, just red sand and dust. But before the Aboriginal people were cleared from the area in 1953, it was relatively fertile, with tall mulga trees, native yams and tomatoes, and a water hole or two.

It is possible that these people will eventually be able to return to their traditional land, 3,000 square kilometres of which is now fenced and patrolled. The area could again be the hive of activity it was during the Fifties and Sixties, but this hinges on talks between the British and Australian governments, which have been taking place at a diplomatic snail's pace since last November.

In an attempt to move things along, and prop up his government's position, Robert Tickner, Australia's Minister for Aboriginal Affairs, will raise the issue at a United Nations conference on indigenous peoples in Geneva at the end of this month.

The nuclear contamination took place during the Fifties, when the British, under an agreement with the Australian government, tested nuclear weapons and components. Testing continued until the Partial Test Ban Treaty in 1963. The Australian government has favoured a partial clean- up scheme, costing about Adollars 100m ( pounds 45m) at 1990 prices, but this seems to depend on a large contribution from the British government.

A clean-up would have the site resembling the cover of a science-fiction book about mining on the moon. Giant plastic bubbles would be used to contain dust sifted by truck-sized vacuum cleaners. The most contaminated area, however, would receive a low-tech treatment: a high fence.

The problem area is not the explosion zone, known as 'ground zero', of the bomb tests at Maralinga and the nearby Emu Fields. A report by the Technical Assessment Group (Tag), a team of Australian and British scientists, said the major components of fallout have short half-lives and decay quickly, and therefore 'radiation levels close to all nine ground zeros at Maralinga and Emu Fields are now low'.

The problem was the additional tests, mostly done in 1960 and 1961, designed to find out, for instance, whether a warhead travelling on a truck would detonate in a road accident. Warheads containing plutonium were set on fire or destroyed with chemical explosives.

The charts produced by Tag show that these trials, known as Vixen B, resulted in radioactivity levels above the 5 millisieverts- a-year safety limit. The Vixen B tests involved more than 20kg of plutonium and an equal amount of enriched uranium.

The only practical treatment for these areas, the Tag scientists decided, was to bulldoze the topsoil away and bury it. Scraping a foot of soil from an area of 300 square kilometres (115 square miles) and burying it in trenches would cost a staggering Adollars 450m ( pounds 200m) - perhaps two or three times as much if the trenches need extra lining for water run-off.

Luckily for the Australian government, the local Aboriginal people have said this is unacceptable. Denuded of its topsoil and vegetation, the area would be an open wound on the Earth's surface for at least a century. 'They don't want one natural disaster after another,' says Archie Barton, administrator for the Maralinga Tjarutja, a landholding and representative body. So a fence will go up. Date of removal: about 250,000 AD.

A cheaper solution involves removal of only the top few centimetres of contaminated material. Two US companies are offering vacuum-cleaner systems that are said to be capable of doing this. But these truck-sized monsters still require the vegetation to be stripped away, and cause significant environmental damage.

Mike Costello, a scientist at the Australian Nuclear Science and Technology Organisation and a programme manager in Tag, watched one of the devices suck up a pile of sand on a flat surface - a long way from a full test. Dr Costello says he has little confidence in vacuum technology's abilities over large areas.

The immediate area of the Vixen B tests, where surface radioactivity is many times the safe level, has been ploughed as part of Operation Brumby, the British clean-up in 1967 which, under the original agreement, legally freed Britain from all further liability for the site. The result is a radioactive mixture of soil and rubbish, such as wire cable and steel sheet.

One problem with areas such as this is their attraction for souvenir hunters. It sounds unlikely - but it has been a frequent concern both at Maralinga and the Monte Bello islands off the coast of Western Australia, site of Britain's earliest bomb tests. Rob Rawson, head of the Test Site Management Unit in Canberra, receives occasional requests from four-wheel-drive clubs wanting to hold rallies, which are always turned down. Other visitors include camels, wild descendants of those brought to take supplies to desert towns before the coming of the railways.

But the greatest complexity and risk lies not in surface contamination, but in pits scattered across the site, used to dump radioactive materials and general rubbish. Record keeping has been poor. The quantities are large: pits near the Vixen B site contain almost 2,000 tons of contaminated soil and debris, while a pit at nearby Kuli contains seven tons of uranium in what one report describes as 'shallow burial'.

The problem is that normal weathering processes can bring items to the surface, including, in one case, a whole Land Rover.

One option is to dig up and classify the debris and then rebury it more carefully. But this would be expensive. Dust would be a serious problem, so the Tag reports show how plastic bubbles, 24 metres long and five metres high, could be placed over the pits by crane during excavation. Air locks and extensive air filtration would be needed, as would careful attention to control of the microclimate: working in a protective suit inside a plastic bubble in central Australia during midsummer could be dangerous.

But new technology might offer an alternative. Pacific Northwest Laboratory, a company based in the US, has developed a technique known as in situ vitrification (ISV), which turns soil into a hard, crystalline solid without it being touched. 'We're very interested in ISV because we don't want to put people at risk,' Dr Costello says. The technique involves pushing electrodes into the soil and passing gigantic electric currents through them. The soil is heated to 2,000 C - hot enough to burn any plant or animal matter and actually melt the earth. When it cools, any radioactive substances are trapped inside a solid block of earth. A recent test consumed power at 3.8MW - enough for a large housing estate in mid-winter - and produced a block weighing 700 tons.

The availability of cash will determine which, if any, of these techniques is used. Mr Tickner says 'Maralinga is of enormous concern to Aboriginal people', but his own government is not prepared to do any work until the question of Britain's contribution is settled. A relatively small sum of Adollars 13m ( pounds 6m) would give the Aboriginals two-thirds of the area back simply by realigning the existing fences to allow access to 1,920 square kilometres (740 square miles) of uncontaminated land. But Mr Tickner says this 'would not provide a comprehensive solution'.

The Ministry of Defence says its obligations have been fulfilled, although it is still considering making a contribution to costs. This could result in British companies being awarded some of the contracts, an attractive political side-effect.

(Photograph omitted)