Contractors working in protective, pressurised suits have been painstakingly sifting radioactive waste and toxic chemicals yards from children running around in a school playground.

But nuclear experts insist there is no danger to pupils at Chilton Primary School -- despite the discovery of live war-time munitions, including 1,100 small practice bombs, 12,000 rounds of small arms ammunition, and mines, on the site.

Paul Atyeo, Atomic Energy Authority project manager, said the main risk to children and the public -- including householders in nearby Severn Road -- was the accidental release of hazardous dust from the 18-acre former bomb dump, on the edge of the Harwell International Business Centre site.

"All the work has been carried out in temporary, tented buildings designed to prevent dusts leaving the site," he said.

"The two-year project has been subject to very careful checking and monitoring for radioactivity and air quality." Last year, the school, houses in Severn Road and Chilton Garden Centre were evacuated when what proved to be an empty 500kg German bomb casing was unearthed at the site.

The area is known locally as the bomb dump because of its use as a war-time ammunition store by the RAF.

After the war, the RAF airfield was taken over by scientists as Britain's main centre for research into nuclear power.

For a number of years a cocktail of chemical and laboratory waste was dumped into unlined pits next to the school site.

The materials included potentially lethal beryllium, which is widely used in the nuclear industry. Some of the materials were contaminated with low-level radioactivity -- all of which is now being excavated for removal to licensed landfill sites, or in the case of the radioactive waste, to a specialist site at Drigg, in Cumbria.

During a media tour of a multi-million-pound project to clean up parts of the former Harwell Laboratory complex, Mr Atyeo said work on two of the main areas was now nearing completion.

The restoration of the southern storage area, or bomb dump, adjacent to the school, and a concrete bunker under the Harwell Rugby Club pitch known as the 'catapult pit', is the largest and most complex environmental clean-up project of its type in the country.

It will pave the way for the redevelopment of part of the site with 275 new homes.

The Chilton Field housing scheme is part of a long-term programme to redevelop most of the Harwell and Chilton site as a hi-tech technology and science park, including housing and a 240-bedroom hotel.

But, in granting outline permission for the scheme, the Vale of White Horse District Council made it a condition that the southern storage area be cleaned up and landscaped as a recreation area.