 At the University of Birmingham in March 1940 , Otto Frisch and Rudolf Peierls examined the theoretical issues involved in developing , producing and using atomic bombs in a paper that became known as the Frisch – Peierls memorandum . They considered what would happen to a sphere of pure uranium @-@ 235 , and found that not only could a chain reaction occur , but it might require as little as 1 kilogram ( 2 @.@ 2 lb ) of uranium @-@ 235 to unleash the energy of hundreds of tons of TNT . The first person they showed their paper to was Oliphant , and he immediately took it to Sir Henry Tizard , the chairman of the Committee for the Scientific Survey of Air Warfare ( CSSAW ) . As a result , a special subcommittee of the CSSAW known as the MAUD Committee was created to investigate the matter further . It was chaired by Sir George Thomson , and its original membership included Oliphant , Chadwick , Cockcroft and Moon . In its final report in July 1941 , the MAUD Committee concluded that an atomic bomb was not only feasible , but might be produced as early as 1943 . 
