Queensland test 'was not a nuclear bomb'

Confusion surrounded claims yesterday that Britain, Australia and the United States exploded a nuclear bomb in a tropical rainforest in Queensland in the 1960s.

An article in New Scientist magazine quoted declassified Australian cabinet documents, which it said revealed that a 50-ton nuclear bomb was detonated in 1963 at Iron Ridge as part of a secret military experiment codenamed Operation Blowdown.

It said the records, which are in the National Archives in Canberra, described the operation as "an investigation into the effects of nuclear explosions in a tropical forest", while a medal citation for a sergeant who supervised it referred to "an airburst nuclear device".

However, both the Ministry of Defence and the Australian Defence Department insisted that a conventional bomb made of TNT had been detonated close to the ground to simulate the effects of a 10-kiloton nuclear explosion in the air.

An Australian National Parks and Wildlife Service ranger, Mick Blackman, who is based near Iron Ridge, said records in his office showed that the test used conventional weapons to simulate the effects of a small nuclear explosion. He said soldiers and scientists built a 126ft observation tower which extended above the canopy of the rainforest, and that its remains could still be seen at the site.

Meanwhile, Australian journalists who examined the same cabinet papers yesterday said they made no mention of testing a nuclear weapon, but instead discussed a proposal by the US to use Iron Ridge to test nerve gases.

The idea was rejected in 1965, partly because of the difficulties foreseen in keeping the operation secret.

One cabinet submission said: "We would think in view of our recent commitments in South Vietnam, we would do well to remain free of being open to charges from Communist propaganda among Asians of preparing the ground for use of chemical or biologicalweapons."