The draft report of a year-long scientific study by a Defense Department contractor, completed last November, has concluded that GIs at the 1957 nuclear weapons test called Smoky may have received twice the external radiation to their bodies that was shown by film badges worn at the time.

The study, according to the Defense Nuclear Agency officials who have reviewed it, noted that the badges, which were the only record made of radiation exposure, did not pick up neutron doses.

Many of the Smoky participants, the study found, had been at other Nevada test shots during the summer of 1957, including one where they were close enough to get a dose of immediate neutron radiation.

In addition, the study found that the GIs either had their backs to the blast or were bending over and thus the badges on their chests recorded radiation that had already passed through their bodies.

Agency officials, who had contracted for the study, said yesterday it was a "competent piece of work" which "showed in a broad sense the badges are about right."

They had feared that doses might have been "10 times what was measured," one source said.

Even at twice the currently recorded dose levels, the agency sources maintained, radiation exposures for the Smoky GIs would still be well below levels now considered safe from any health effects.

Despite the official view, the study is bound to fuel the existing controversy over whether leukemia and other cancers that have turned up in Smoky veterans can be traced to low levels of radiation absorbed during the Nevada nuclear tests.

Hundreds of such veterans or their widows have filed for service-connected disability benefits, saying their cancers or other ailments stem from radiation exposure during the tests.

Until now, the Veterans Administration has turned down almost all cases, often citing low film-badge readings as proof that the subsequent cancer could not have been connected with test exposures.

The traditional government position, that low-level radiation exposure could not cause cancer over the long term is now under challenge from a number of sources.

Eight Smoky participants have, in the intervening 20 years, developed leukemia. A Department of Health, Education and Welfare study, now almost completed, has already determined the eight leukemias are more than twice the number that should normally have occurred in a group the size of Smoky.

A White House-ordered task force is studying what should be done to settle what has become a heated medical controversy over the long-term health effects -- if any -- of low-level radiation.

Its findings are expected to be circulated in the next week and its final recommendations thereafter.

The study sponsored by the Defense Nuclear Agency was designed to identify the radiation levels to which the soldiers at Smoky were exposed.

Science Application Inc., the McLean, Va., firm that made the study, reconstructed Smoky and nine other shots from the summer of 1957. The firm traced the radiation levels and the movements of troops in order to determine the levels of exposure.

One of the first discoveries was that many of the Smoky troops had observed other shots and had had additional exposure from residual radiation picked up while rehearsing for Smoky in areas dosed during previous tests.

At one of the shots prior to Smoky, called Doppler, a number of soldiers were in trenches close enough to the explosion so that they were exposed to immediate, or prompt, neutron radiation. Their badges were not equipped to record neutrons and the firm's study only estimated the effects from that blast.

Nuclear agency officials said yesterday that the study is being reviewed by the Army, and some of its assumptions will be checked through ex-GIs who took part in the tests.

The study is not expected to be publicly released by itself. Rather it is scheduled to be published later this year as part of a much larger report on Smoky and other 1957 tests.

Meanwhile, Science Application Inc. is now looking into what additional radiation -- if any -- soldiers may have received internally by inhalation, which could not be recorded by the external film badges.

Soldiers and observers have said radioactive dust was present in the air while troops went through their postshot maneuvers at Smoky and other Nevada tests.