HARRISBURG, Pa. (AP) _ Nearly two decades after the accident at the Three Mile Island nuclear plant, area residents who believe it made them ill have not presented cases strong enough for trial, a federal judge has ruled.

U.S. District Judge Sylvia H. Rambo Friday dismissed all 2,000 damage claims against the plant, saying she had tried in vain to find a legally acceptable way to allow the cases to continue.

``The grave consequence of the court's decision ... is obvious,'' Rambo wrote in a 97-page memorandum accompanying her one-paragraph order. ``Thousands of individuals who believe that they have suffered adverse medical effects as a result of the TMI accident will not have an opportunity to have their claims heard by a jury of their peers.''

But ``the scarcity of evidence'' supporting their claims, and legal standards governing the award of summary judgment, made dismissal of the lawsuits necessary, she said in a decision released Friday evening.

The lawsuits were filed by central Pennsylvanians who blamed exposure to radiation released in the March 1979 nuclear accident for health problems including leukemia and other cancers.

They had been consolidated into one case. A trial had been scheduled to begin this month.

Ray Dotter, a spokesman for General Public Utilities Corp., of Parsippany, N.J., which owns the plant, said the ruling reflected scientific findings.

``Thousands of pages of evidence were submitted, the judge heard many days of expert testimony, but no valid reliable evidence was submitted to contradict what science has said about the accident,'' he said.

Laurence S. Berman of Philadelphia, one of the plaintiffs' attorneys, said he was unaware of the decision and declined comment. Two other plaintiffs' lawyers did not return phone messages late Friday.

Eric Epstein, who serves as chairman of the Three Mile Island Alert watchdog group, predicted the plaintiffs will appeal.

``Clearly there's enough evidence to substantiate the claims of adverse physical as well as adverse psychological effects.'' he said.

The U.S. Supreme Court in April refused a request to rule out possible punitive damages awards for the plaintiffs.

Rambo said the plaintiffs could not show that the public was exposed to a 10-rem radiation dose, which both sides have agreed can cause physical harm.

The defense said repeated studies showed the public received no more than 100 millirems of radiation. A rem equals 1,000 millirems; the average American is naturally exposed to about 360 millirems each year.

Rambo earlier this year dismissed the plaintiffs' expert witnesses, saying the methods and opinions of the experts _ including including some Russian scientists who had studied Chernobyl and other accidents _ were scientifically unsound.

Plaintiffs were unable to persuade the 3rd U.S. Circuit Court of Appeals to reinstate the experts.

A combination of mechanical and human failures allowed Three Mile Island's Unit 2 reactor to lose cooling water in March 1979. Part of the core melted and some radioactive gases were released into the air near Harrisburg.

It remains the nation's worst commercial nuclear accident. It took almost $1 billion and more than a decade to remove the damaged nuclear fuel.

State health officials have said studies show no evidence to link the radiation release with any adverse health effects other than stress.