Operation Morning Light--""the most massive search for nuclear debris ever undertaken""--was conducted after the Russian Cosmos satellite disintegrated over northern Canada last January. Leo Heaps presents a straightforward account, quoting officials and engineers by name, and managing at the same time to point up the ludicrousness of our nuclear society. The Russians really had claimed that their satellite was ""fail-safe,"" but an ""unpredictable fault"" led to the accident, and we learn that neither President Carter nor Canadian Prime Minister Trudeau was given all the facts about the impending disaster ""until the very last day."" The full ramifications of the event may never be known. By April, particles of enriched uranium were turning up hundreds of miles from the original site, and subsequent checks of areas once declared ""clean"" were revealing new radioactivity. Even now, only ten percent of the radioactive core has been recovered, and officials admit they don't know where the rest of it is. While the satellite was still on one of its last erratic orbits, there was even worry that its core might heat up and cause an explosion ""many times more powerful"" than Hiroshima. The significance of all this goes beyond the Cosmos incident. Heaps shows us the many unknowables and risks involved in dealing with nuclear materials, noting that by 1985 more than 10,000 man-made satellites will be orbiting the earth. A quick but responsible wrap-up.