Much of the stimulus for the treaty was increasing public unease about radioactive fallout as a result of above-ground or underwater nuclear testing , particularly given the increasing power of nuclear devices , as well as concern about the general environmental damage caused by testing . In 1952 – 53 , the US and Soviet Union detonated their first thermonuclear weapons ( hydrogen bombs ) , far more powerful than the atomic bombs tested and deployed since 1945 . In 1954 , the US Castle Bravo test at Bikini Atoll ( part of Operation Castle ) had a yield of 15 megatons of TNT , more than doubling the expected yield . The Castle Bravo test resulted in the worst radiological event in US history as radioactive particles spread over more than , affected inhabited areas ( including Rongelap Atoll and Utirik Atoll ) , and sickened Japanese fishermen aboard the '' Lucky Dragon '' upon whom " ashes of death " had rained . In the same year , a Soviet test sent radioactive particles over Japan . Around the same time , victims of the atomic bombing of Hiroshima visited the US for medical care , which attracted significant public attention . In 1961 , the Soviet Union tested the Tsar Bomba , which had a yield of 50 megatons and remains the most powerful man-made explosion in history , though due to a highly efficient detonation fallout was relatively limited . Between 1951 and 1958 , the US conducted 166 atmospheric tests , the Soviet Union conducted 82 , and Britain conducted 21 ; only 22 underground tests were conducted in this period ( all by the US )
Castle Bravo
Castle Bravo
Partial Nuclear Test Ban Treaty