The nuclear fast breeder reactor, once the nation's highest energy research priority, is in deep trouble, and some administration officials are saying privately that it may, in fact, be dead.

At best, these and other officials say, the breeder will not be needed until the end of the century, and possibly not until as late as 2025. By that time, many in the field believe, some other, more attractive technology, such as solar power or nuclear fusion, will have made the breeder unnecessary.

On the record, the Department of Energy says it is now spending $14 million a month on the Clinch River, Tenn. breeder reactor President Carter set out to kill, and this year will spend more than half a billion dollars on overall breeder research and development.

But at the department, questions about the long-term future of the breeder program are met with measured answers. Energy Secretary James R. Schlesinger Jr. says the administration does have a breeder policy, and that policy is to continue studying options.

At the State Department Joe Nye, one of the architects of the administration's nonproliferation policy, offers another view, "We are agnostic on the breeder reactor." Nye opposed the Clinch River breeder because it would have generated plutonium, which in turn can be used to fabricate atomic weapons.

Back at the Energy Department Deputy Secretary John F. O'Leary says, "You have a lot of time before you have to make a hard decision on the breeder." Asked when a decision would have to be made at the earliest about commercialization, O'Leary says, "It is something like 1990."

But the Energy Department's operative approach, laid out in closely held briefing papers, is the "hedge option." That strategy comes down to avoiding a toe-to-toe confrontation with the nuclear industry, the research community, and the Congress over funding, while putting off the critical decision to license a demonstration reactor until the next decade.

This is not lost on the nuclear industry.

"Without licensing there can be no breeder," says Milt Shaw, former head of the Atomic Energy Commission.

Carl Walske, head of the Atomic Industrial Forum, offers another view: "It is like being told you can't have grandchildren."

Some anti-breeder lobbyists, such as Jim Cubie of the Union of Concerned Scientists, agree with Shaw and Walske's assessment. "The administration strategy has been to put off a forced decision on the breeder; instead they have gone along with the Congress on funding."

In the industry's view, breeders are synonymous with the future of nuclear power, because they literally "breed" their own fuel, stretching known supplies of uranium. "Without the breeder we have decades; with it we have centuries," adds Walske.

Why has the breeder skidded so much from its position as President Johnson's, Nixon's, and Ford's top energy research project? And why has the Carter administration, which initially sought to shelve the Clinch River breeder reactor in March, 1977 for proliferation reasons, found still other reasons to put off licensing a breeder?

The reasons are varied, but in the end come down to economics and new findings about the extent of uranium resources.

A major attraction of the breeder is the fact that it creates new fuel, thus easing the nation's dependence on natural uranium.

But DOE and some nuclear industry officials say there is more reason for optimism about recoverable uranium than there was a few years ago. A study recently completed by University of Arizona geologist DeVerle Harris concluded that there are between 12 and 32 million tons of U308 "yellowcake" at a cost of $50 a pound or less. This projection of supply is sharply higher than an earlier study performed by the National Academy of Sciences.

These optimistic uranium forecasts, buoyed by new discoveries in Canada and Australia, have O'Leary saying, "The more you know about uranium the more there is." Bullish uranium forecasts, at the least, undercut the urgency of the breeder program. If proven correct, they could push back by decades the time when a breeder would be necessary.

There have also been sizeable cuts in anticipated uranium demand in the United States and elsewhere.There has been an unannounced moratorium in the United States simply because few new nuclear plants have been ordered.Projected demand for uranium has fallen off elsewhere as well. James Reddington of the Paris-based International Energy Agency says the IEA has reduced its forecasts of installed nuclear capacity in the industrial countries in 1985 by a third over the last years.

Another obstacle to breeder development that tends to undercut the short-supply uranium argument is anticipated gains in conventional reactor efficiency.

Nearly two years ago the Energy Research and Development Administration (a DOE predecessor agency) estimated that the efficiency of conventional reactors could be increased by about 8 percent.

Today, according to John Deutsch, DOE's director of basic research, efficiency can be increased up to 30 percent by the end of the century. "This makes a difference," says DOE's Marvin Moss. "We could improve efficiency by 15 percent by 1985, and add another 15 percent by the year 2000."

So far, adminstration funding for boosting reactor efficiency has been meager: next year's budget increases the amount spent from $10 million to $18 million.

Princeton's Frank Von Hipple, an outspoken breeder opponent, says new efficiency could allow "putting off a decision on the breeder a long time, possibly as much as 50 years."

Most troubling for the breeder's supporters, however, are the growing worries about the breeder's own economics.

A DOE strategy paper now making the rounds concludes that the breeder could cost as much as 1.75 times more than a conventional reactor. And a yet unpublished IEA study has concluded that breeder-reactor-generated electric power could end up costing twice as much as electricity from conventional reactors. Even more troubling is an IEA finding that the cost reduction, expected as reactor production is increased, would not take place until the 95th reactor were constructed.

Breeder proponents such as Wallace Behnke disagree. "No one knows for sure how much it will cost to build a commercial fast breeder reactor; we would expect costs 25 to 50 percent more than today's reactors" says Behnke, head of the Clinch River project's management group.

There are also growing -- or at least slight cracks -- in the nuclear industry's oft-repeated charge that the Europeans, Japanese, and Soviets are going ahead with their breeders, while the United States breeder program is not moving towards licensing.

England's electric utility industry within the last weeks called for shelving it's four-reactor $10 billion breeder program. Sir Francis Tombs, chairman of England's Electricity Council, said, "There is no point in building a breeder reactor now and then wait 20 years until we need to use it." North Sea oil discoveries account for some of this, but Tombs lave the cutbacks to uncertainty over rising costs and public acceptance of nuclear power.

Meanwhile, some American officials say in private that French officials running the West's most aggressive breeder program say that part of the rationale behind the French program is to provide "insurance" against manipulation of France's uranium supply -- all of which has to be imported. A similar argument is being made by Japan, which also is resource-short.

Both countries are also keenly aware of what happened to uranium prices, which rose from $6 to $41 when the so-called uranium cartel, including Gulf Oil, Canada, Australia, and South Africa, was ruling the world uranium market.

(Even then, DOE officials are quick to point out that the French are only spending $365 million this year on the breeder, compared with more than $500 million for the United States.)

While the breeder program is caught in uncertainties over economics and the availability of uranium, to say nothing of the will of the Congress -- which increasingly regards Energy Department research and development spending as a warmly eyed political dollop for the folks at home -- one thing is clear: the gloss on the breeder program has worn off.

Next year the administration and the Congress are likely to spend as much if not more on fusion than on the breeder. Following a major breakthrough in fusion last summer, elated DOE officials and Princeton scientists said that fusion generated electrical power could be commercial by 2025.