The Soviet Union has launched a new naval reconnaissance satellite with a nuclear reactor on board, the first time the Kremlin has taken such a step since the same kind of spacecraft ran into trouble and burned up over Canada two years ago, leaving a trail of nuclear debris on the ground.

Administration officials, who told reporters about the launching yesterday, were clearly unhappy with Moscow because the space shot came while the United States is working at the United Nations to try and develop internationally binding safety requirements for putting nuclear power sources into outer space.

The military significance and timing of the Soviet launching, however, may have more immediate significance.

The launching came on April 29, four days after the aborted U.S. effort to rescue the American hostages in the Tehran embassy.

Just before launching the rescue attempt, the U.S. aircraft carrier Nimitz sped away from a Soviet spy ship that had been trailing it, and apparently was able to launch the rescue helicopters on their secret mission without notice.

The use of nuclear power sources aboard reconnaissance satellites usually means that they carry high-powered radar aboard, which requires lots of power for operation. The new satellite is passing daily over the Iranian Ocean and Middle East area and may well be meant to keep the Kremlin from being surprised again by providing radar surveillance of the U.S. fleet.

The new satellite -- designated Cosmos 1176 -- is said to be a "twin" of Cosmos 954 which reentered the earth's atmosphere and burned up on Jan. 24, 1978, in one of the most spectacular accidents of the space age. Bits of radioactive debris were spread over a wide area of remote, northwest Canada, touching off widespread diplomatic protests.

To prevent such accidents, these satellites normally are supposed to be boosted from their operating altitude of about 150 miles above the earth to some 600 miles so that they stay in space for hundreds of years. But the boost mechanism on Cosmos 954 failed and the satellite came down.

Since then, the United States has argued at the United Nations to get an international agreement on safety standards for spaceborne reactors, notification of launch and responsibility for clean-up in an accident.

The Soviets argue that existing regulations -- which don't have agreed safety codes -- are sufficient.

The administration thus far has made no private protests to Moscow but officials said they did not rule that out. There is no indication of any problems thus far with the new satellite, they said.