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Just-released documents reveal that six more Army weapons trials likely scattered radioactive dust to the Utah winds in the 1950s. They were so big they released 11 times more radiation than all the other 68 known similar tests combined.

The newly uncovered Dugway Proving Ground tests released more than 141,000 curies of radioactive tantalum-182, compared with between 12,400 and 13,000 curies released by the 68 others. A curie is the unit used in measuring radioactivity.The combined amount from all tests - more than 153,000 curies between 1949 and 1953 - is 10,000 times more than the 15 curies of radioactive iodine released by the infamous near-meltdown of the Three Mile Island nuclear reactor in Pennsylvania.

The information comes from Energy and Defense departments documents requested and obtained by Sen. Bob Bennett, R-Utah, which he released Friday.

A year ago, all of the now 74 known or suspected weapons trials were secret. But congressional and Deseret News probes have revealed them piecemeal since then.

The tests were designed to develop non-nuclear bombs and other weapons that could scatter radioactive dust over an enemy. President Clinton has already ordered the Advisory Committee on Human Radiation Experiments, which he formed last year, to review the danger and ethics of such tests at Dugway.

The new documents also contain some good news. They outline Army studies in 1987 and 1989 that concluded that no lingering radiation threat still persists today from the tests at Dugway - even though they were potentially very dangerous at the time.

"My first concern - and the reason I pushed for the documents - is to make sure no danger exists now," Bennett said.

While Army studies concluded that it does not, Bennett said his staff is working with scientists at the Army's Aberdeen Proving Ground in Maryland to provide one more review of data.

If it also concludes no current danger exists, Bennett said he then wants to find "whether anyone was damaged by the tests and how to make sure we're not that sloppy in the future."

He said he will keep pressuring for more information until those questions are answered. Bennett is on the Senate Governmental Affairs Committee, which has for years been investigating government radiation experiments.

The two biggest tests mentioned in the new documents were apparently planned for or near May 23, 1953. Documents do not confirm whether they actually occurred, but an Army study in 1989 about potential lingering radiation assumed that they did.

Little information about them is given in that 1989 report except that one test planned to deposit 100,000 curies of radioactive tantalum over 4 square miles at the Dugway base. The other planned to deposit 10,000 curies over 1 square mile.

The 1989 report said it found mention of plans for those two tests in another report about a related field experiment in March 1953 at Yuma Proving Ground, Ariz. It was designed to see if the Dugway tests would create a problem with airborne radiation.

"The report concluded that there was little likelihood of airborne radioactivity hazard from the proposed operations," the 1989 report said.

The four other newly revealed weapons were much smaller and occurred on Nov. 7-8, 1952. In them, different shapes of munitions were exploded to see which would spread radiation the farthest. They released a total of between 1,100 and 1,612 curies.

The Army studies about possible lingering threats from the old tests noted that the tantalum-182 used has a half-life of only 115 days - meaning it loses half its radioactivity by decay in about three months. And the tests occurred 40 years ago.

"With this in mind, the level of radioactivity today resulting from these tests is, of course, completely negligible and is undetectable with the most sensitive radiation counting instruments," Assistant Defense Secretary Harold P. Smith Jr. wrote Bennett.

In the 1989 radiation hazard study, Army officers walked and drove throughout the test areas with sensitive radiation-measuring devices - and found nothing except normal background radiation, except in one area where beryllium waste had been buried in a trench.

While test areas may not be dangerous today, documents show the Army believed it was dangerous back in the 1950s. Several tests were conducted to develop con-tamination methods by taking advantage of radiation in the test areas.

Also, tests evaluating how well different construction techniques protected against radiation were also conducted in the test areas.

Some documents about such tests - released previously - show photos of workers without shirts in the hot desert having co-workers hold Geiger counters near them to see how well different materials were shielding radiation.