The Supreme Court yesterday ruled unanimously that courts cannot require the Food and Drug Administration to ensure that injections used to execute death row inmates are "safe and effective."

The decision overturns a 1983 ruling by a federal appeals court here that temporarily had blocked states from using lethal drugs until they were tested by the FDA. Chief Justice Warren E. Burger had blocked that ruling pending a full review by the high court.

In another case, the court ruled, 5 to 4, that the U.S. Court of Appeals for the Federal Circuit has the power to review decisions by the Office of Personnel Management and the Merit Systems Protection Board that deny retirement benefits to federal employes.

The court also ruled, 8 to 1, that federal appeals courts can review decisions by the Nuclear Regulatory Commission not to suspend the licenses of nuclear power plants.

Lethal injections, permitted in about 15 states, have been used eight times in executions since the Supreme Court reinstated capital punishment nine years ago.

The latest use occurred last week in Texas. In that case, it took an orderly more than 30 minutes to find a vein in the arm of a convicted murderer in which to insert a needle because, officials said, his veins had collapsed from drug abuse. Witnesses said the man died calmly once the needle was inserted.

Death row inmates in Texas and Oklahoma had asked the FDA to review the drugs, saying that they had not been approved for such use and that it was likely they would not cause a quick, painless death.

The FDA declined to review the drugs, saying it had the discretion to decide not to do so. But U.S. Court of Appeals Judge J. Skelly Wright ordered the agency to study the drugs to ensure that prisoners would not suffer cruel or unusual pain during an execution.

Justice William H. Rehnquist, writing for the court yesterday, said agencies, like prosecutors, have substantial discretion in deciding when to launch investigations, such as the drug study. The court said judges, as a general rule, should not overturn those decisions unless Congress has indicated that an agency's discretion is limited. The case is Heckler v. Chaney.

The retirement benefits case came after the OPM denied retirement disability pay to a civilian Navy employe, saying that his chronic bronchitis was not severe enough for him to qualify.

The man's appeal to the MSPB was turned down and the U.S. Court of Appeals for the Federal Circuit said Congress had declared that MSPB decisions were final and not subject to court review.

Justice William J. Brennan, writing for the majority, said that although the appeals court could not review factual issues, it had the power to review MSPB and OPM decisions if legal issues were raised.

Michael J. Kator, an attorney for the 500,000-member National Association of Retired Federal Employes, said the case could reach beyond the issue of court review of disability retirements.

The appeals court had ruled previously "with a view that its powers in reviewing the MSPB were limited," Kator said. "I think this ruling will mean that the Federal Circuit is going to have to keep an eye on the MSPB."

Justice Byron R. White, writing in dissent, said the law made clear that Congress intended to block judicial review of MSPB decisions.

The case is Lindahl v. Office of Personnel Management.

In the nuclear plant case, Florida Power & Light Co. v. Lorion, a woman wrote the NRC in 1981 about her concerns over safety at a nuclear reactor near her home outside of Miami. She asked the NRC to investigate, but the commission declined.

The federal appeals court here declined to intervene, saying it lacked the power to do so.

The high court, in a decision written by Brennan, yesterday reversed the ruling, concluding that Congress intended to have appeals courts review such decisions.