One of the Carter administration's top concerns now that the United States is terminating its defense commitment to Taiwan is how to keep the Taipei government from trying to develop nuclear weapons, authoritative sources said yesterday.

U.S. experts believe that if Taiwan decided to launch a major effort to acquire nuclear weapons, it could produce its first atomic device in less than two years.

The question of how to dissuade Taiwan from taking this step is a very real one, for knowledgable sources believe that following President Nixon's visit to Peking in 1972, Taipei decided to move closer to a nuclear weapons capability.

On two separate occasion, the United States learned of Taiwanese efforts to develop a plutonium reprocessing capability-a process that would give Taipei material suitable for atomic bombs.

The United States brough strong pressure on the Taipei government following the most recent incident in 1977, arguing that Taiwan could better servve its security interests by maintaining its relationship with the 1nited States that by trying to develop nuclear weapons.

Top U.S. officials say that the Taipei government apparently came to this same conclusion, and for the past year-and-a-half, Taiwan has made no further effort along these lines.

But now that the United States has been decided its commitment to defend Taiwan, some experts fear the Taipei government may re-examine this question.

One member of the ruling Nationalist Party's Central committee called yesterday for immediate development of nuclear weapons to help increase the island's security.

Beyond having a large number of trained nuclear scientists and engineers, Taiwan has accumulated enough spent fuel from the large research reactor at its Institute for Nuclear Energy Research to provide the plutonium for a least a half-dozen Hiroshima-sized atomic bombs.

While Taiwan's first bombs would be bulky devices that probably would be deliverable only by large transport planes or commercial airliners, they still would pose a threat to Shanghai, Canton and other major population centers of eastern China.

The Taipei government might conceivably decide that even such a primitive nuclear capability would be sufficient to deter the Peking leadership from launching an invasion of Taiwan.

U.S. experts, however, feel the idea that Taiwan could develope a credible nuclear deterrent is unrealistic.

Most believe that long before Taiwan actually achieved such a nuclear capability, China-which already has an inventory of several hundred atomic and hydrogen weapons-would take military action to bring such a threat to an end.

Thus, the task facing the Carter administration, in the view of one key government official, is to persuade Taiwan that its best interest continues to lie in a "declining, residual American relationship rather than in a effort to develop a weak, vulnerable nuclear deterrent."

Despite the changes that will take place in the formal relationship, the United States will continue to have considerable leverage.

Taiwan has alreaddy put one American-built nuclear power plant into operation, and five additional U.S. atomic power stations are either on order or under construction.

Taiwan's only source of the low-enriched unranium fuel for these power stations-which by the mid-1980s will be generating about one-third of the island's electricity-is the United States.

Carter administration officials says there is no reason why U.S. cooperation with Taiwan's civilian nuclear power program should not continue under the revised legal arrangements to be worked out between the two countries.

In fact, officials privately express the hope that no effort will be made by Congress or the Nuclear Regulatory Commission to block a continuation of the civilian nuclear relationship.

"This nuclear cooperation provides us with a lot of leverage," a key U.S. source said.

For one thing, the U.S. Nuclear Nonproliferation Act passed last spring mandates a cut-off of all nuclear supplies to any state that appears to be trying to develop an atomic weapons capability.

"The price of any future misstep by Taiwan would be the loss of a significant part of the country's electrical capacity," a U.S. source said.

The United States might also decided if it detected any nuclear moves of a disturbing nature to end whatever continuing arrangements may be made to supply American conventional arms, ammunition and spare parts to Taiwan.

The Carter administration will also insist as part of the arrangement for civilian atomic cooperation that Taiwan continue to allow all its nuclear facilities to be "safeguarded" and inspected regulary by the International Atomic Energy Agency.

This will not create any new legal problems for Taiwan. It has continued to allow the IAEA to inspect its facilities even though it was ousted from the agency in 1972, at the time Peking was admitted to the United Nations.

But perhaps the strongest argument the United States can be make against any Taiwanese inclination to develop nuclear weapons is that such a move would almost certainly provoke the military showdown it would be designed to deter.

Beyond the chance of detection at an early stage by China's own intelligence agents on Taiwan, the Taipei government would certainly have to consider the possibility that any suspicious nuclear activity uncovered by the United States might be passed along to Peking.

Yet another argument against Taiwanese pursuit of a nuclear capability is the feeling of many people on Taiwan that their government should not even consider using such weapons against fellow Chinese.

But for all the factors arguing against Taiwanese development of nuclear weapons, U.S. experts feel this is a "major concern" that bears extremely close watching in the years ahead.

"There indeed is a very serious danger," a top U.S. official said yesterday. "And the only thing we can do is caution them against it, watch and worry."