The Three Mile Island nuclear accident has caused a slowdown in Japan's atomic power program, prompted antinuclear demonstrations around the world and added emotional force to demands that the construction of new reactors be halted.

Nonetheless, the French government defied environmental groups and opposition politicians yesterday to give its formal approval to the construction of two more reactors cooled with pressurized water, similar to the one at Three Mile Island.

In oil-starved Japan, though, Atomic Energy Safety Commission Chairman Tokuo Suita said the nuclear power program there will be slowed down because of the Three Mile Island accident.

The Japanese government had planned to more than double the amount of energy produced by atomic reactors in the next six years. But officials there said local residents will put up stiffer resistance to new plants and will force stricter safety measures.

As an indication of the spillover from the American accident, a group of Japanese environmentalists, trade union leaders and Communist Party members Monday demanded that government and utility company executives stop operations at the country's 19 nuclear plants.

These incidents highlight a worldwide debate that has gained force with the detailed reports of the American nuclear accident as nations try to strike a balance between the possible hazards of nuclear power and the ever increasing cost and dwindling supplies of oil.

This debate started long before the accident, but antinuclear forces have seized on it as added ammunition in their fight.

In West Germany, for example, where 35,000 antinuclear activists demonstrated Saturday against plans to build an underground nuclear waste dump in the northern part of the country, one newspaper suggested that Three Mile River accident "may signal an early end to the nuclear age."

Court rulings and demonstrations in West Germany already have discouraged the construction of new nuclear plants although 15 are presently in operation.

The nuclear waste issue caused voters in Austria to reject by a bare majority government plans to place in operation a $600 million nuclear plant that is already built.

In sweden, the State Power Board closed one of two reactors that are the same type as the one at Three Mile Island. Officials at the Ringhals nuclear power station on Sweden's west coast said they were forced to close the reactor because of a leak in a steam generator-the second one since January.

While Lars Gustafsson, the technical director of the power board, said the leak is another like the Pennsylvania accident and the reactor should be working again in a week, that incident, coupled with the Three Mile Island accident is expected to breath, new life in Sweden's nuclear power debate.

As in other countries around the world, the government there faced demands from its opposition that a referendeum be held on the disposal of nuclear wastes.

Swiss voters last month narrowly rejected complicated new requirements for nuclear plant construction, including provisions that would give nearby residents veto power over each plant's location. The government feared this would have shut down the three existing Swiss reactors and prevented any new ones from being built.

Another referendum is scheduled for May on a new nuclear safety law in Switzerland, and a Swiss government official said the Three Mile Island accident casts a "a long shadow over that vote."

Denmark's parliament is in the midst of a debate on nuclear power, with a final decision on whether to build reactors scheduled for next year. Newspaper and opposition politicians called the Three Mile Island accident a dark warning of what could happen if Denmark goes nuclear.

British Prime Minister James Callaghan assured Parliament that an accident similar to the Pennsylvania mishap could not happen in Britain because it uses different kind of nuclear reactors-ones that are cooled by gas instead of water, which reduces the danger of a high pressure or temperature buildup.

"I can assure the country that the incident which took place in Harrisburg could not take place here because of the different type of reactors," said Callaghan. "We have been very wise in concentrating on a safer type of reactor.

Callagan's confident words were echoed by his energy secretary, Tony Wedgwood Benn, who said he has resisted great pressure to switch to American reactor technology.

"A lot of people will be looking at British gas-cooled technology with great interest." said Benn.

Nonetheless, Liberal Party leader David Steel questioned Callaghan about the construction of a new nuclear plant in Scotland without public hearings. Callaghan replied that the plant's construction had been carefully considered by the government.

A number of countries have rushed nuclear experts to the United States to provide first-hand reports to their governments on the Three Mile Island accident.

Among others, these include France, West Germany, Denmark, Japan and Belgium, and are in addition to scientific and energy attaches regularly attached to the embassies here. The Nuclear Regulatory Commission ran a special briefing yesterday for the foreign experts.