LONDON — BRITAIN has decided to halt research on fast nuclear reactors and mothball the know-how already achieved in a field in which it was once a world leader. The decision to withdraw from the European Fast Reactor program (EFR), announced Nov. 20 by Tim Eggar, minister of energy, is the latest sign that a source of power once thought to hold enormous promise has lost its attraction in Britain.
It is also being seen as further evidence that the British nuclear industry is being thrust onto the defensive by conservationist pressure and by reassessments of Europe's future energy needs.
British nuclear scientists who have contributed to 40 years of research on so-called fast-breeder reactors have attacked the pull-out from the EFR, on which Britain spends l13 million British pounds ($20.5 million) a year.
Clifford Bloomfield, former director of a prototype fast reactor at Dounreay, Scotland, which is to be shut down, said pulling out of the EFR was "irresponsible and unwise" and would enable France and Germany, which plan to remain in the program, to benefit from research that has cost Britain l4 billion British pounds since the early 1950s.
To a chorus of approval from supporters, Mr. Eggar told the House of Commons that there was no foreseeable future for nuclear plants that make more efficient use of fissionable material than conventional reactors.
"We have consulted the nuclear-power industry, which did not see fast reactors as a high priority and was unwilling to commit funds to further research. The government has decided to withdraw funding for fast breeder research after March 1993," Eggar said.
His comments drew a rebuke from leaders of Britain's nuclear industry, who issued a joint statement saying they greatly regretted the move.
Brian Eyre, director of AEA Technology, Britain's main nuclear-research agency, said he was "deeply disappointed" because the EFR project was "within reach of building a commercial demonstration plant."
The economic case for fast-reactor technology, a British energy official said, had been undermined in recent years by the plentiful supply of uranium used in old-style magnox reactors, pressurized-water reactors, and advanced gas-cooled reactors. The demonstration plant that the EFR team is working on, he said, might be able to produce electricity more cheaply than a pressurized-water reactor, but capital costs would be much higher.
Even dedicated supporters of nuclear energy concede that the industry has entered a difficult phase in which its future is by no means assured.
Lord Marshall, a nuclear engineer and former chairman of Britain's Central Electricity Generating Board, said that until stocks of North Sea natural gas began to run down, nuclear energy would have problems justifying itself.
But Mr. Bloomfield noted that ending Britain's part in the EFR would cost nearly 300 jobs, nearly all of them highly skilled. He forecast a "new brain drain" as British scientists and technicians moved to France, Germany and Japan, where their talents would be "properly recognized."
Britain's withdrawal from the EFR was announced as doubts began to grow about the future of a huge new nuclear-reprocessing plant at Sellafield, Cumbria. The l1.8-billion British pounds plant - built with the help of funds from European countries and Japan, which want to use it to reprocess spent fuel from their nuclear-power stations - has been attacked by environmental groups that say it will produce unacceptable levels of toxic gases.
The plant, which is set to open in 1993, was to have produced plutonium for use in fast reactors, but that option is fading. British Nuclear Fuels, the operator, says it has reprocessing contracts for 10 years, but after that little is known about world requirements for reprocessing facilities.
Forecasts published by the Organization for Economic Cooperation and Development suggest that, with few exceptions, countries will scale down their use of nuclear-generated electricity in coming years. Britain currently derives about 24 percent of its electricity from nuclear sources, but that is set to fall to about 17 percent over the next decade.
Sweden, the United States, and Germany also anticipate percentage cutbacks. Japan, France, and Canada are planning to increase their percentages over the same period.