The Supreme Court yesterday ruled that the government need not consider the "psychological stress" suffered by neighbors of a nuclear power plant before authorizing the plant to begin operation.

The court struck down a controversial order of the Court of Appeals for the District of Columbia, handed down after the Three Mile Island nuclear power accident in 1979. The appeals court decision was an unprecedented extension of the law requiring environmental impact statements for major projects involving the federal government.

Stress among those living near a plant arising from the fear of another accident, the appeals court said, must be taken into account in preparing an impact statement.

Yesterday's unanimous decision was an important victory for both the Nuclear Regulatory Commission (NRC), which had opposed the requirement, and the nuclear power industry, which said it would drag out an already cumbersome regulatory process.

In addition, it removed the possibility that difficult psychological considerations--fear of crime stemming from construction of a housing project, for example--might be required for all major federal projects. This prospect had caused considerable stress and fear among many officials and industries.

Justice William H. Rehnquist, writing for the court, said the National Environmental Policy Act, which requires impact statements, mandated assessment only of the direct physical and environmental impact, not of "every impact." The relationship between a project and psychological stress is too vague and indirect to be included, he said.

"Anyone who fears or dislikes a project may find himself suffering from 'anxiety, tension, fear and a sense of helplessness,' " Rehnquist wrote. Those sentiments are policy matters for Congress, he said. The law, he added, was not "intended to give citizens a general opportunity to air their policy objections to proposed federal actions."

The psychological stress requirement was sought by a group of residents of the Harrisburg, Pa., area near Three Mile Island when they were trying to prevent the Metropolitan Edison Co. from restarting the reactor left undamaged by the accident there. After the NRC rejected the request, the group, called People Against Nuclear Energy, went to court, arguing that their concern about a "recurring catastrophe" could cause them significant psychological harm.

"We do not mean to denigrate the fears of PANE's members, or to suggest that the psychological health damage they fear could not, in fact, occur," Rehnquist said in reversing the appeals court. "Risk is a pervasive element of modern life," Rehnquist said.

But "it would be extraordinarily difficult for agencies to differentiate between 'genuine' claims of psychological health damage and claims that are grounded solely in disagreement with a democratically adopted policy," he said in Metropolitan Edison vs. PANE.

In other action yesterday, the court significantly limited the ability of the federal government to investigate the basis of the prices it pays contractors for billions of dollars worth of supplies.

The justices said government auditors may have access only to business records directly related to the manufacturing costs of the products it purchases, not to broader information concerning indirect costs, such as advertising and research and development.

The decision stemmed from a long-standing dispute between the pharmaceutical industry, which sells drugs on a fixed-price basis to the Defense Supply Agency and the Veterans Administration, and the General Accounting Office, which was attempting to conduct a broad probe of pharmaceutical pricing in the United States.

The government argued that the "direct costs" covered only about 9 percent of the actual price paid for the products. But Justice Sandra D. O'Connor, writing for the 5-to-4 court in Bowsher vs. Merck & Co., said Congress purposely limited access to private industry records to prevent unnecessary "snooping" by the government.

GAO officials said the decision applied only to fixed-price purchases and not to such massive projects as weapons and aircraft procurement.

Justice Byron R. White, joined by Justice Thurgood Marshall, dissented from much of the decision, saying it could deny the government access to records that have "a critical bearing on the prices charged and that would be of central importance to a GAO inquiry into the fairness of these prices."

Justices Harry A. Blackmun and John Paul Stevens also disagreed with parts of O'Connor's ruling.