The Virginia nuclear disaster that the Pentagon simulated in Nevada last week turned out to be not as disastrous as first feared, a federal agency said yesterday.

The Federal Emergency Management Agency said that Port Gaston--the fictitious Navy town that was site of the mock accident--has been declared safe for rehabitation, four days after the "crash" of a military helicopter carrying three nuclear weapons spread radioactive debris throughout the test area.

Because almost all of the debris has been cleared, "people will now be allowed back in," said Jim Holton, spokesman for the exercise dubbed NUWAX-83. NUWAX, which involved more than 1,100 federal, Virginia state and local officials, was designed to test government responses to a real nuclear emergency by simulating a disaster with as much realism as possible.

To do this, the Pentagon created Port Gaston on a test site that was used for atmospheric atomic bomb tests in the 1950s. Virginia officials were flown to the site by the Defense Department and participated in the $3.6 million exercise.

Holton said a final "casualty" report showed that seven people would have died and seven would have been injured as a direct result of such an accident.