The Nuclear Regulatory Commission, reversing its position of 11 months ago, yesterday approved the export of eight tons of enriched uranium to India.

The action came despite the fact that India in 1974 successfully tested an atomic bomb and so far has not agreed to comprehensive safeguards the new U.S. Nonproliferation Act will require of all nations receiving American enriched uranium.

When a similar application was made last year, the commission refused on a 2-to-2 tie to approve the necessary export license. President Carter then authorized the shipment; Congress, which under the law could have blocked it, did not, and the uranium was exported to India.

India needs enriched uranium to fuel its nuclear power plant at Tarapur.

The plutonium India used in its bomb is believed to have come from spent nuclear fuel originally supplied by Canada. The contract under which the United States sells uranium to India prohibits such reprocessing, but there are nagging fears that without effective safeguards, India could violate the restrictions.

The approval yesterday afternoon came on a 3-to-2 vote, with Commissioners Victor Gilinsky and Peter Bradford voting against the license as they did last time, and NRC Chairman Joseph M. Hendrie and Commissioners Richard Kennedy and John Ahearne voting for the license.

This time, the difference was Ahearne, who was appointed by President Carter to fill the fifth seat on the NRC last July after the tie in April.

In a written opinion explaining his vote for the license, Ahearne said that while India has not agreed to allow the United States to inspect all its nuclear facilities, talks are going on that could lead to such a development.

"Although the degree of optimism (in the negotiations going on) fluctuates from day to day, I believe progress has been made," Ahearne wrote. "Congress clearly understood that difficult negotiations would be required with India, provided a grace period for those negotiations and in general expected exports could continue to India during this period."

In the Nonproliferation Act of 1978, Congress specified that no application could be granted for the export of enriched uranium to any country not agreeing to "full-scope" safeguards 18 months after enactment of the law. It also specified no uranium export could be made to such a country two years after enactment.

The fuel export license that NRC approved yesterday was the 28th such shipment marked for the Tarapur nuclear station in India. The 29th export application for eight more tons of enriched uranium is already on file with the NRC, meaning it will come to a vote before the Nonproliferation Act deadline in September.

But if India has not agreed to allow all its unclear facilities to be inspected, including its reprocessing plant outside Bombay where it extracted the plutonium for its first bomb, the 30th export application it makes for uranium to refuel the Tarapur facility may well be denied.

"We are faced with the distinct possibility that India will interpret this result as freeing it of any reciprocal obligations under the U.S.-India agreement," Commissioners Gilinsky and Bradford wrote in their dissent. "In that event, the protection now afforded all U.S. nuclear exports to India under the agreement may well cease to exist."

Bradford said after the vote that India has implied that if the United States cuts off fuel shipments, then India is free to extract plutonium from any spent fuel it has from previous shipments. Before yesterday, the United States had shipped 95 tons of enriched uranium to India for the Tarapur station, enough to produce several tons of plutonium in the spent fuel after the uranium is burned up.