U.S. Tests Released Radioactive Isotopes, Soviets Say

The Soviet Union accused the United States on Thursday of releasing radioactive isotopes into the atmosphere in connection with nuclear tests conducted in February and March.

A formal Soviet protest was delivered to U.S. Ambassador Jack F. Matlock Jr. It charges the United States with violating a 1963 treaty banning tests in the atmosphere.

Gennady I. Gerasimov, chief spokesman for the Soviet Foreign Ministry, told reporters that Soviet monitors had verified the presence of radioactive isotopes in the atmosphere.

“No state except the United States . . . was testing nuclear weapons” at that time, he said, adding that “the discharge was greatest on March 18, following a nuclear explosion that day.”

The isotopes detected by the Soviets could not have resulted from an accident at a nuclear plant, Gerasimov said, but only from a nuclear explosion. He did not say whether the radiation level was high enough to be a danger to human beings.

The Soviet government, after failing to persuade the United States to join it in a moratorium on nuclear testing, began testing again in February. The United States promptly charged that the Soviets had contaminated the atmosphere beyond Soviet territory. Moscow denied the charge.

Gerasimov said that Washington made the charge in an effort to detract attention from its own tests.

“The Soviet Union,” he said, “condemns Washington’s violations of its international responsibilities, which are of special concern because they are regular and systematic.”