The Clinton administration yesterday acknowledged the federal government has a responsibility to help private workers who were injured, some fatally, by exposure to the metal beryllium while laboring at nuclear weapons plants.

"We made a mistake in not recognizing that our nuclear weapons workers were injured in the course of their work," said Energy Secretary Bill Richardson. "That is stopping today."

Richardson made the admission at a news conference, where he announced the administration's support for a bill that would treat these ill "contract workers" as federal employees for purposes of medical benefits and disability claims.

Beryllium, a light and brittle metal, is a component in nuclear bombs, as well as in satellites, missiles and weapons guidance systems. Although the Department of Energy is the sole American manufacturer of atomic weapons, most of the work is actually done by private contractors.

The department estimates about 26,000 workers have been exposed to beryllium at federal sites, the most important of which are in Colorado, Washington, Tennessee, Ohio, Pennsylvania and New Mexico. About 120 people have been diagnosed with berylliosis, although a senior Energy official said he expects the number to reach at least 500 in the next few years if the bill passes.

About 10 percent of the people exposed to beryllium dust develop something akin to a low-grade allergic reaction. However, in some cases, this can lead, decades later, to permanent scarring of the lungs. Sufferers are often breathless with mild exertion, and many die of respiratory failure.

Traditionally, workers with berylliosis found it hard to collect under state worker's compensation laws, which were created to handle workplace accidents, not diseases appearing decades after a toxic exposure. When they turned to the federal government for help, beryllium's victims were rebuffed with the argument that they were private, not public, employees.

"This is a new era in the Department of Energy in its treatment of workers," Richardson said. "Those who fell ill from occupational illnesses during the Cold War were as much casualties of war as those who fell in Europe, in the Pacific, in Korea, in Vietnam or in Desert Storm."

The proposed bill would provide the workers with the same benefits federal workers get. Those include tax-free recompense of up to 75 percent of lost wages; no-deductible medical treatment by doctors of the patients' choice; and a provision to "make whole" the wages of beryllium workers found to be sensitive to the metal and forced to take lower-paying jobs. Survivors of people who died from toxic exposure to beryllium are eligible for lump-sum payments.

The exact details of the bill haven't been worked out. It will be offered by Rep. Paul E. Kanjorski (D-Pa.), who described its genesis as a "classic, Civics 101 case" of representative democracy.

A year ago, a constituent, Alfred Matusick, of West Hazleton, contacted Kanjorski with a story of his illness and unsuccessful attempts to get compensation. He had worked at a beryllium processing plant for 24 years. Soon after he started work in 1957, he was severely poisoned in a beryllium dust accident that caused a temporary illness called pneumonitis.

Kanjorski said he was convinced Matusick was "an average American citizen who had been harmed by his government and his employer."

Now 67 and unable to walk up three stairs without getting winded, Matusick yesterday said he was "very grateful" for the government's change of attitude.

The proposed legislation apparently will have bipartisan support. Among those at yesterday's news conference was Rep. Zach Wamp (R-Tenn.), whose district includes the nuclear plant at Oak Ridge.

"That these people have been affected [by beryllium] there is no question," Wamp said. "We can't make it right, but we can make it economically just."

Richardson said the White House will convene officials from several agencies to decide whether the benefits proposed for contract beryllium workers should be also offered to workers exposed to radiation, asbestos and other toxic materials at defense plants.

Beryllium's hazards were recognized in the late 1940s. Massachusetts General Hospital kept a national registry of people with berylliosis between 1950 and the early 1970s. The list, now held by the National Institute for Occupational Safety and Health, in Morgantown, W. Va., may help survivors of victims prove their cases.

CAPTION: Energy Secretary Bill Richardson, with new Assistant Secretary Carolyn L. Huntoon, backs legislation to help workers injured by exposure to beryllium.