London — Margaret Thatcher has decided that the British Royal Navy should no longer have to depend on the United States to supply fuel for its nuclear submarine fleet.
In a fresh indication that the Thatcher government means what it says when it talks of maintaining a truly independent British deterrent, the Prime Minister has given the go-ahead for building a uranium- enrichment plant to produce nuclear-submarine fuel.
Since Britain's Polaris fleet was established in the 1960s, the ships have used fuel supplied under contract by the US. This has made them dependent on American good will.
But beginning in the mid-'80s that situation will change radically. A uranium enrichment plant at Capenhurst, Cheshire, will produce the fuel, using the gaseous diffusion technique.
According to defense experts, the enriched uranium could also be used in the construction of a new generation of nuclear weapons, including the so-called neutron bomb, but there appear as yet to be no plans to use the Capenhurst facility for bombmaking.
Nuclear experts privately admit, however, that the facility will probably be used to produce nuclear fuel for a new fleet of British submarines equipped with US-supplied Trident C-4 missiles.
Such a fleet is expected to begin going into service in the '90s, and Britain may decide to build its own Trident warheads.
Orders to build the nuclear-fuel factory were issued by Defense Secretary Francis Pym, a strong advocate of an independent British deterrent.But Mrs. Thatcher has been showing close personal interest in Britain's future nuclear-defense program and chairs the Cabinet subcommittee that makes top-level defense-policy decisions.
The Thatcher government has yet to make the formal decision to build a Trident nuclear fleet. But in defense circles there is a strong belief that the Capenhurst project means the decision now can be taken for granted.
The project gives an indication of Britain's attitude to a possible SALT III treaty between the US and Russia. If negotiation of SALT III became a reality, the Americans could expect to find themselves under pressure from Moscow to end the arrangement whereby they currently supply Britain with missile fuel for submarines.
With its own enriched-uranium factory, Britain would not be affected by those Soviet pressures.
The Capenhurst facility will be operational by 1985. Until 1963 the British Defense Ministry maintained Capenhurst as a uranium plant, then shut it down. Nuclear engineers will thus not be starting entirely from scratch in implementing the new program.
By the time a Royal Navy Trident is due to go into service, Capenhurst should be capable of operating at its planned full capacity.