Early tests in the seas where a Soviet nuclear submarine caught fire and sank near the Arctic Circle last week fortunately show no signs of major radiation contamination, although Norwegian scientists are preparing measurements at greater depths.

The probes appear to bear out Soviet assurances that there is no danger of radiation leaks from the submarine's nuclear power plant or any nuclear warheads that might have been aboard.However, it's better not to be too complacent in the light of environmental disasters on the high seas in recent months, including the oil spills at Valdez, Alaska, and earlier in the Antarctic.

The sinking of the unnamed Soviet sub, which killed 42 of the 69 crew members, apparently was not connected to any nuclear mishap. Fire reportedly broke out as a result of electrical short circuits while the vessel was cruising underwater. It surfaced long enough for some of the crew to escape and sank when explosions cracked the submarine's hull.

According to reports from Moscow, the crew was able to safely shut down the nuclear reactor before the ship went to the bottom.

But it's not the only N-sub to go down at sea. The Soviets have lost three other nuclear-powered submarines, and the United States has lost two. Whatever radiation is leaking - if any - from these other disasters has not been measured, but radiation has been loosed in other accidents, including a 1961 incident in which a Russian submarine crew died from radiation poisoning after a mishap in the Baltic Sea.

Aside from concerns about radioactivity, the loss of the latest submarine may be a serious setback to the Soviets. The Kremlin had been using the ship - built in 1983 - for experimental purposes to improve its submarine fleet and to test advanced weapons. The sunken ship was the only one of its kind in the Soviet navy and won't be easy to replace.

This is only the latest problem in the Soviet submarine program. Some U.S. experts say the Soviet navy has had 200 serious accidents with submarines since 1975. Norwegian specialists say that 85 percent of the Soviet strategic submarine fleet is in the dock for repairs at any one time, a stunning number, if accurate.

While those figures may ease U.S. concerns about Soviet military capability and readiness, it is not exactly reassuring to know that such an accident-prone navy is sailing the world's seas in nuclear-powered ships and carrying nuclear-tipped missiles.