Two years ago, a Western world worried by its growing dependence on Arab oil thought it saw a ray of hope on nuclear power, which, the Organization for Cooperation and Development predicted, would expand rapidly. By 1985, the OECD said, the nuclear energy would provide the equivalent of 15 million barrels a day of oil, more than all of the Western Europe now imports.

Just last wqeek, OECD gave its patrons, the rich West and Japan, the bad news. By 1985, nuclear power is expected to supply only the equivalent of little more than 9 million barrels a day, a staggering drop of nearly 40 per cent.

What has happened in two short years? OECD begins its list of explanations this way:

"The continual markdown of nuclear expansion results from resistance to nuclear energy by conservationists and environmentalists. . . "

A key policy urged to expand energy supply is "moderation of environmental requirements of new energy development, partivularly coal and nuclear power."

The report reflects thinking in the nuclear power establishment of OECD member governments. So it probably exaggerates the importance of the nuclear opposition whilt simultaneously ignoring its political concrens.

John Surrey of the Science Policy Research Unit at Sussex University has made the most thorough study yet compiled of the resistance to nuclear power. He is convinced that =nearly all the cutback would have taken place anyway" for economic reasons. "The opposition was the icing on the cake that contributed to increased capital costs."

Like other students of the nuclear slowdown, Surrey believes that the more modest growth noe foreseen in Western economics coupled with an inflationary buildup of financing and construction costs - both due in considerable measure to the big jump in oil prices since 1973 - have been far more important than citizen opposition in curbing the plants.

But the OECD has put its finger on a central point. There has been a climbdown in plans for nuclear expansion and determined groups of citizens have played some part in this.

The opposition has taken dramatic form in France and West Germany, two nations like Japan that bet heavily on nuclear power, to escape the Arab and oil company yoke.

At Brokdorf, West Germany, last fall, 600 security guards turned tear gas, water cannons and dogs on several thousand demonstrators trying to halt the building of a plant on a site surrounded by a moat and a 10-foot high concrete wall topped by barbed wire.

The governor of North Rhine-Westphalia, West Germany's most industrialized state, has refused to license any more nuclear plants until the problem of their radioactive waters is solved. Dump your "atomic excrements" somewhere else, he declared.

At least three nuclear installations in France were bombed in 1975. The government there has cut back from 40 to 25 or 30 the number of plants it expects to order by 1980.

The is no evidence, however, of a widespread public demand to halt nuclear power. Its opponents lost a half dozen referenda in the United States last year. But where the opposition forms, as economist Surrey has observed, it is acute and effective.

Four rural communities in France held votes on nulear plants in 1975. Three largely well off and stable voted against. But a fourth, in an area where worked-out iron mines had left a residue of big umemployment, approved the building.

In Britain, a royal commission under Sir Brian Flowers recently delivered a terrifying report on the dangers from plutonium economy, one that uses nuclear plants breeding large quantities of the poisonous, explosive man-made element.

Flowers foresaw the possibility of accodent on a catastrophic scale, terrorists stealing the stuff of which bombs are made, a clampdown on civil liberties to protect plants from theft or sabotuers, plutonium in the hands of a Col. Muammar Qaddafi or an Idi Amin.

The report create barely a ripple. A call for a "mass" demonstratrion in Trafalgar Square brought out only a few hundred and on a Saturday, too.

Britain had not ordered a new nuclear plant since 1969 because its sluggish economy does not need one. This lack of visibility had muted the foes.

Sweden is frequently cited as an example of a nation that has voted against nuclear power. The facts, in that land of hard-headed materialists, are otherwise.

It is correct that Thorbjorn Falldin, campaigning on apledge not only to stop but roll back nuclear plants, is now premier. But for the first time in 12 years, his party's share of the vote dropped and three-quarters of the Swedes voted for parties favoring nuclear expansion.

Falldin, in office, has had to junk his pledge. He has charged one reactor and approved building of others, although he says they will not be turned on until their safety is assured.

Despite this mixed picture, the nuclear foes can claim considerable success. They can do so even in the face of well substantiated claims that the nuclear industry so far has a better safety record than most.

A study for the ole U.S. Atomic Energy Commission calculated that the worst imaginable reactor accident could cause 3.300 deaths and injure or poison 45,000. But this was likely to happen only once in a billion years of reactor operation. The low probability, however, may still sound unconvincing to those at a site where a new plant is going up.

More recently citizens and politicians have began to worry about atomic garbage, the wastes that must be buried for thousands of years before their radioactivity dies out. In West Germany, that waste has been buried in salts cavern in Lower Saxony that are siad to be geologically stable. But there, too, the governor has said he will take no more until he is convinced there is no risks of leaks.

Apart from those frightened by their nearness to nuclear installtions, a new wave of opposition has been building largely on political grounds.

These people worry about nuclear explosives falling into the wrong hands.

Fuel burned in today's nuclear plants is chemically cooked or reprocessed to be used again, thereby saving on limited uranium. But in this reprocessing, plutonium, the ingredient of bombs, is created and shipped to the nuclear plant for reuse.

What if a terrorists siezed a shipment, nuclear foes ask. Twenty pounds are enough to make a crude but devastating bomb, and the technique for making one is now weell known.

Another private study has predicted that Britain could, by the end of the century, destroy its civil liberties to protect its plutonium. The report envisages thousands of armed guards, widespread wiretapping, opening of mail and similar techniques to guard against and detect theft.

Governments are also concerned about the misuse of nuclear power and its prospect for enlarging the select club that can now make bombs. That is why the United States has called for halting the sale of reprocessing plants, the plutonium producers, to nations that lack the bomb. In Britain, the government has stopped the planned expansion of its plant that reprocesses fuel for Japan and others.

A new type of power plant, the fastbreeder reactor, lies in the heart of the concern expressed by Britain's royal commission. It creates more plutonium than it burns, an economical technology that also multiplies bomb-making capacity around the world.

The royal commission urged the government to postpone "as long as possible" any decision to plunge ahead with fastbreeders. Eminent scientists from East and West at the Pugwash conference last summer took a similar stance. They agreed that both reprocessing of used fuel and the introduction of fastbreeders could be put off for 10 years without any shortage of uranium for existing plants.

It was once taken as an article of faith that fastbreeders would not only provide most of the nuclear power of the future but also meet growing demands for all energy until the end of the century. Now Surrey of Sussex thinks the scientific doubts are so strong that fastbreeders may never come into widespread use.

The mounting tide of opposition, both scientific and lay, has alarmed the atomic establishment - govenrments, energy commisssions, reactor builders and electric utilities. They are engaged in unpublicized studies of ways to nuetralize it.

One of the most provocative is conducted by the Risk Group, an international collection of anthropologists, economists, social psychologists, physicists and others in Vienna. The Risk Group was set up by the International Atomic Energy Agency, the U.N. body devoted to promoting nuclear energy in the Third World, and the International Institute for Applied System Analysis. This last is a product of the Lyndon Johnson's administration, a think tank that draws on scholarss from both East and West to apply for the business-school technique of systems analysis to social problems.

The Risk Group leaderr is Harry Otway, an American nuclear physicist. He says, "we are simply trying to understand how peoples' attitudes are framed, how to integrate their social values with technological systems."

He vigorously denies that his project aims at defusing nuclear opposition, but at least some of its work points in that direction.

Are governments then faced with a Hobson's choice, either taming their opponents or halting nuclear expansion? Surrey says, "No, there is another route, meeting the legitimate concerns of the nuclear foes."

He points to several instances where this is being done or considered.

The U.S. Arms Control and Disarmament Agency, for example, suggest that fears over reprocessed plutonium could be allayed by a new technique. It would cook spent fuel but not separate plutonium from uranium. Then the product could be used again, but its bomb making substance would be difficult to extract.

The safety and civil liberties problems might be eased through nuclear parks, grouping huge complexes of plants in one remote and more easily guarded place.

Governments have already yielded to the fears of those near nuclear plants. Five years ago, they planned to build new ones in the center of towns and cities: nobody makes blueprints for that anymore.

Finally, a host of safety rules have been introduced, both for domestic reactors and export sales. They make nuclear energy more costly and prolong its birth, but they also meet some of the oppositions demands.

The sharp slowdown in nuclear output, largely a product of the world economic situation but partly due to the protests of scientists and citizens, also forcing attention toward new energy sources.

Research and development of energy from the sun, wind and waves has been starved of funds, Surrey observes. Nuclear power has gobbled io a lion's share. But with the pressure to slow nuclear growth, some shift in research money is now likely.