Nuclear Tests Conducted by U.S., Soviets

The United States and the Soviet Union both conducted underground nuclear tests Saturday, the two governments announced.

The American test was conducted 1,030 feet beneath the surface of Rainier Mesa at the Nevada Test Site, a Department of Energy spokesman said.

The 9 a.m. blast, code-named Mission Ghost, was a weapons-effect test with a yield of less than 20 kilotons (equivalent to 20,000 tons of TNT), spokesman Jim Boyer said.

It was the eighth nuclear test in Nevada announced this year and brought to 667 the number of announced nuclear tests at the site since testing began there in 1951, Boyer said.

The official Soviet news agency Tass said the Soviet test, held at the main Soviet test grounds in the Gegelen Hills near Semipalatinsk, in Central Asia, had a yield of between 20 kilotons and 150 kilotons--within the limits of the 1974 Soviet-U.S. Threshold Test Ban Treaty.

The blast, the seventh since Moscow suspended a 19-month moratorium on testing earlier this year, was aimed at “upgrading military technology,” Tass said.

Military analysts say that means the blasts were specifically aimed at improving warheads.

Three others were said by Tass to have been linked to “fundamental research” or to “checking the physics of nuclear explosions”--apparently a reference to the effect of nuclear blasts.

The unilateral test moratorium was first proclaimed by Kremlin leader Mikhail S. Gorbachev in August, 1985, and extended several times as he sought to persuade the United States to join in.