January 25, 2003 By THE ASSOCIATED PRESS LONDON, Jan. 24 - Alan Nunn May, a British atomic scientist who spied for the Soviet Union, died on Jan. 12 in Cambridge. He was 91. The Times and the Daily Telegraph reported his death but did not give a cause. One of the first Soviet spies uncovered during the cold war, Dr. Nunn May worked on the Manhattan Project and was betrayed by a Soviet defector in Canada. His unmasking in 1946 led the United States to restrict the sharing of atomic secrets with Britain. His discovery ignited a search for other spies inside the Manhattan Project and led indirectly to Britain's producing its own weapon. Born in Birmingham, in central England, Dr. Nunn May won a scholarship to study physics at Cambridge University, where he was a contemporary of another future spy, Donald Maclean. While lecturing at King's College in London, Dr. Nunn May joined a Communist Party group. By World War II, he was working on a secret British project to develop radar and had allowed his party membership to lapse. In 1942, he joined a team of Cambridge scientists who, as part of the Manhattan Project, were studying the feasibility of German plans to use heavy water to build an atomic reactor. A year later, we was transferred to Montreal, where he was recruited by Soviet military intelligence. In July 1945, when Dr. Nunn May told his Soviet controller that he was due to be sent home soon, Moscow decided to get as much out of him as it could. On July 9 of that year, a week before the Americans tested an atomic bomb, he passed small amounts of enriched uranium to his Soviet handler, later providing details of the bomb dropped on Hiroshima. In return, he received $200 and a bottle of whiskey. Shortly after the war ended, Igor Gouzenko, a lieutenant in the Soviet military intelligence agency, and cipher clerk at the Soviet Embassy in Ottawa, defected with documents giving details about Soviet agents, including Dr. Nunn May. By then, Dr. Nunn May had returned to Britain, where he was arrested and put on trial and sentenced to 10 years' hard labor, of which he served six. He always insisted that he was simply sharing vital scientific knowledge. "The whole affair was extremely painful to me, and I only embarked on it because I felt this was a contribution I could make to the safety of mankind," he once said. "I certainly did not do it for gain." After leaving jail, Dr. Nunn May returned to Cambridge, where he married Hilde Broda, a doctor. Dr. Nunn May is survived by his wife, a son and a stepson. Copyright 2002 The New York Times Company