Reports from the plant, which is about 25 miles west of Pittsburgh, indicated there had not been a radioactive release from the plant, said David Smith, director of the Pennsylvania Emergency Management Agency.

The emergency was declared at the plant's No. 2 reactor unit at 5:36 a.m. The leak was called an "unusual event," the least serious of four classifications of power plant emergencies.

At one point, radioactive water was spilling onto the floor of the containment building at the rate of 12 to 20 gallons a minute, said Neil Sheehan, federal Nuclear Regulatory Commission spokesman. No workers were exposed.

The reactor was shut down and workers in protective suits were checking the leak, Sheehan said.

The other three classifications of emergencies are an alert, a site-area emergency and a general emergency. Only one general emergency has ever been declared at a U.S. nuclear plant, after the March 1979 accident at Three Mile Island near Harrisburg.

Rocky Flats was one of a series of weapons plants built after World War II for the cold war nuclear arms buildup. Now, it is one of 113 sites in 30 states that the Energy Department is cleaning and rehabilitating, an undertaking that includes treating huge amounts of contaminated ground water, weapons-grade plutonium and spent nuclear fuels. By some estimates, it will cost the federal government as much as $212 billion over the next seven decades.

The main activity at Rocky Flats, which opened in 1951 and closed 48 years later, was building plutonium detonators, or "pits," that were then shipped to Texas for assembly into nuclear weapons. It was a complex process to complete and, now, to dismantle, involving the stabilization and packaging of tons of leftover toxic metals as buildings were razed and areas were cleared. The materials are trucked to disposal sites in New Mexico and Georgia.

Over the years, several incidents have reflected the dangerous nature of the mission. Among hundreds of small fires that occurred through spontaneous combustion of toxic substances, three — in 1957, 1965 and 1969 — burned out of control, sending radioactive dust skyward. In 1966, officials found that 5,000 drums of radioactive material left outside of buildings had leaked in the previous 12 years, causing the largest plutonium contamination on the site.

More recently, Kaiser-Hill has been fined more than $700,000 for safety violations on the project.

The Chernobyl complex, 75 miles north of the Ukrainian capital of Kiev, has suffered a series of accidents since reactor Number Four caught fire and exploded 14 years ago, sending a radioactive cloud across much of Europe.

The station said it had measured no increase in radioactivity after Wednesday's shutdown, but it came on the eve of a decision by the European Bank for Reconstruction and Development on lending $215 million for the completion of two more Soviet-designed reactors.

Ukraine says it cannot afford to switch off Chernobyl, which provides five percent of all its electricity, without Western loans for decommissioning the plant and completing the reactors.

"The reason for shutting down the unit was the discovery of steam in an unstaffed room, number 404," a statement from the station said. The room contains pipes from the primary cooling system, electricity distributors and other equipment, it said.

"Now we are cooling the energy block to find the exact point of the steam leak," it said.

The 1986 Chernobyl disaster immediately killed around 30 firemen, and radiation has since been blamed for the deaths of thousands and a sharp increase in thyroid cancer and other diseases affecting one in sixteen Ukrainians.

SECOND SHUTDOWN IN TWO WEEKS

The unexpected shutdown was the second in as many weeks after cold weather froze and snapped power lines last week, forcing the station to close down because it had nowhere to feed its power.

The last reactor, Number Three, was restarted Friday for its final weeks of operation.

The shutdown took place at 11:04 a.m. in accordance with accident prevention procedures, the station said. A spokesman for Ukraine's atomic energy regulator said technicians would have to inspect the reactor before deciding whether or not to restart it.

Environmentalists in Kiev made a last ditch effort on Thursday to persuade the EBRD not to fund the completion of reactors at Khmelnitsky and Rivne (known as K2R4), which are of a more modern design than those at Chernobyl but designed by Soviet engineers in the 1970s.

The EBRD is due to announce its decision Thursday and its president, Jean Lemierre, has said he backs the move.

A report to the Austrian government, leaked last week by the environmental group Greenpeace, described the K2R4 reactors as hazardous and listed 29 safety issues which were not adequately dealt with, including the safety of steam tubes, fire prevention and seismic activity.

Austria's EBRD representative was due to vote against the loan, and a Dutch EBRD spokesman said the Netherlands would also oppose it. But votes from France, Britain and the United States were expected to be in favor.

A few dozen Ukrainian environmentalists protested outside the EBRD's Kiev office, waving banners saying "No more Chernobyls."

"The EBRD knows it doesn't make economic sense and that it does not guarantee nuclear safety," said protester Yuri Urbanksky. "But it's blackmail from the Ukrainian side in return for shutting down Chernobyl."

"Measures have been taken to limit access to the area of the water outlet and to contaminated points. Work is going on to remove contaminated soil.''

But the source of the pollution was still unclear.

"It has been established that the cause of the contamination is not linked to the operations of the active three reactors at the station. Work is continuing to find the source of the contamination,'' the statement said.

It said there was no radioactivity in the water and fish of the nearby River Don, which flows into the Black Sea.

The ministry said the problem arose on November 30 and work began the next day to gauge the extent of the contamination..

"These individuals, many of whom were neither protected from nor informed of the hazards to which they were exposed, developed occupational illnesses as a result of their exposure to radiation and other hazards unique to nuclear weapons production and testing,'' the president said in a statement.

"While the nation can never fully repay these workers or their families, they deserve fair compensation for their sacrifices. I am pleased to take the next critical step in ensuring that these courageous individuals receive the compensation and recognition they have long deserved.''

The order directs three federal agencies -- the departments of energy, labor and health and human services -- to implement the compensation program.

The White House gave no exact estimate of the cost of the compensation program, but the administration last year estimated the cost to U.S. taxpayers would be about $13 million a year for the next decade.

Energy Secretary Bill Richardson last year apologized to former and current nuclear workers suffering from chronic beryllium disease, various radiation-linked cancers and other occupational illnesses, reversing a decades-old U.S. policy of resisting injury lawsuits from workers who were once employed by private companies contracted to build nuclear weapons.

Since the Manhattan Project developed the first nuclear bombs in the mid-1940s, U.S. workers have been exposed to beryllium, a rigid, lightweight silver-gray metallic element used to make precise nuclear weapons components.

PROGRAM WILL AFFECT THOUSANDS

"We've come a long way since I apologized on behalf of the government last year. This is one of the most meaningful new federal programs in decades, impacting the lives of thousands of Americans,'' Richardson said in a statement.

He said the executive order would ensure that all weapons plant workers -- past, present and future -- would be compensated for illnesses linked to their work, even after the sites where they once worked has shut down.

Chronic beryllium disease is a treatable but incurable disease that destroys the lungs and eventually suffocates the victim. It takes between 10 and 15 years from the inhalation of beryllium to the onset of the terminal illness.

Radiation exposure is also linked to various kinds of cancer.

A report released in September concluded that U.S. nuclear weapons workers may have been exposed to as much potentially deadly radiation as their Soviet counterparts in the early Cold War, and without knowing the risks they ran.

Some of the U.S. workers were exposed to far higher levels of radioactivity in the 1940s and 1950s than prevailing standards prescribed -- comparable to tens of thousands of times the radiation from a dental X-ray -- and rather than being warned of the risk, were deceived about it, said the Institute for Energy and Environmental Research, an environmental watchdog group.

That exposure meant an increased risk of potentially lethal cancer and kidney damage, the institute said in its report.

Under the order, the Department of Health and Human Services (HHS) will provide the scientific analysis and information needed for the Labor Department to appropriately adjudicate claims.

HHS will develop guidelines to determine whether a cancer is likely to be related to a worker's occupational exposure to radiation, establish methods to estimate worker exposure, and develop estimates for those who have applied for compensation.

The White House said a presidential advisory board will be set up to oversee the scientific validity and quality of this work. The order also creates an interagency working group, and directs the Department of Energy (DOE) to publish a preliminary list of facilities where workers may be eligible for benefits, including private contractors.

DOE officials have said 26,330 workers were exposed to beryllium at the 20 nuclear production sites it administers.

Most of the 120 cases of chronic beryllium disease were discovered among current and former workers who worked at DOE plants in Rocky Flats, Colorado; Hazelton, Pennsylvania; and Oak Ridge, Tennessee.

Sue Martin, a spokeswoman for Private Fuel Storage, said the consortium is following an established process for licensing the facility and that the state is a participant. She said the facility will be operated safely.

“What the governor seems to want to do is short-circuit the process and try to replace the established process with politics and legal action,” Martin said.

While details of the lease between the Skull Valley Goshutes and PFS have not been released, the tribe is expected to make a hefty profit.

Leavitt said he is considering new taxes, regulations and possibly even criminal measures to regulate the transportation and storage of nuclear waste under state law.

Opponents worry the Skull Valley site could become a permanent storage site if a proposed site in Yucca Mountain, Nev., is blocked by that state's political leaders.

Critics fear that storage casks could fail, water and air could be contaminated, property values could drop and cruise missiles or jets tested in the area could crash into the site.

However, the Nuclear Regulatory Commission declared the site safe and the casks sturdy. The military said the chances a jet would crash into the casks are extremely low.

The NRC's final decision on the site isn't expected until sometime in 2002. Three other federal agencies must then approve the proposal.