The Reagan administration is considering a controversial application by Westinghouse Corp. to provide a wide range of technical, training and maintenance services for South Africa's two atomic power plants.

The 10-year contract, which would be worth an estimated $50 million, would call for Westinghouse to provide technical assistance, supervisors, technicians and engineers, train South African personnel, make modifications to the plants, and procure equipment and spare parts.

Although the arrangement would not violate the 1978 U.S. Nuclear Nonproliferation Act, U.S. companies are barred from selling nuclear reactors, major components or fuel to South Africa because of that country's refusal to open all its atomic facilities to international inspection.

As result, the United States has backed out of a contract to supply enriched uranium fuel for the two plants, which are being constructed by a French company at Koeburg 17 miles north of Cape Town.

Moreover, a year ago, South Africa was placed on a new list of 63 countries that need specific U.S. Energy Department approval to obtain any American technology for their atomic power programs.

These countries appear to be attempting to develop atomic weapons, or have not signed the Non-Proliferation Treaty or accepted international safeguards on all their facilities. South Africa falls into both categories.

Nevertheless, the Reagan administration, which has been far more flexible than its predecessors in permitting nuclear commerce with South Africa, reportedly would like to approve the Westinghouse application.

The State Department for days has been on the verge of sending the Energy Department its recommendation that the U.S. government approve the Westinghouse application, according to informed sources.

They said that the delay stems less from concern over erosion of nonproliferation policy than from White House uneasiness over the potential political fallout of appearing to be eager to do nuclear business with South Africa.

A group of about 30 congressmen was rushing a letter to the State Department late yesterday expressing "deep dismay" at the prospect of imminent approval of the Westinghouse application.

Although the two power reactors are not likely to be used to aid a South African nuclear weapons program, they will be the first atomic power plants on the African continent and are viewed as of symbolic importance by the Pretoria government and opponents of the apartheid regime.

Last December, the African National Congress, an outlawed black guerrilla group, claimed responsibility for four explosions that damaged one of the Koeburg reactors, forcing South Africa to postpone the start of operation of the power plant until early next year.

Two House Foreign Affairs subcommittees are scheduled to open hearings today on legislation that would tighten the 1978 nonproliferation act and close loopholes that permit the administration to authorize contracts such as the one pursued by Westinghouse.

Tom Christopher, general manager of Westinghouse's nuclear services integration division, said yesterday that the services his company would offer the South Africans are "primarily training in maintenance and management of maintenance. There is very little associated with nuclear per se."

Christopher said the number of Westinghouse employes who would be based in South Africa would range from six to a maximum of 15, depending on the services desired, and that a small number of South Africans probably would visit Westinghouse facilities in its headquarters city of Pittsburgh from time to time for training.

The other two competitors reported in the running for the contract are Framatome and Kraft Werk Union, a German nuclear company.