Arizona National Guardsmen moved into the American Atomics Corp. plant yesterday to begin packing radioactive tritium for removal in a takeover of the plant ordered by the governor.

A company official had warned the takeover could result in "big releases" of tritium, and American Atomics issued a statement later saying any future releases would be the governor's responsibility.

Gov. Bruce Babbitt used emergency powers to order seizure of the tritium, saying he was unhappy with the slow progress toward decommissioning the plant. State officials had alleged the facility leaked radioactive material used to make lighted watches and self-illuminating signs.

In early June, tests found radioactivity in food prepared in the Tucson public schools' central kitchen, across the street from the plant, in a nearby church swimming pool and in urine samples from area residents. The Arizona Atomic Energy Commission voted two weeks later to suspend the plant's tritium operations.

Babbitt said the tritium would be moved to an undisclosed rural location outside the city.

"You can expect big releases. You can expect as much as 100,000 curie releases if they push the wrong valve," said Tom Caffarella, assistant to American Atomics president Peter J. Biehl. A curie is a unit of measure of radioactivity.