 Graves was badly injured in the 1946 laboratory criticality accident at Los Alamos that killed Louis Slotin . Slotin , who was training Graves to replace him in his position as chief bomb assembler for Los Alamos , was demonstrating the dangerous " tickling the dragon 's tail " test to Graves and several other scientists when the accident occurred . Graves , who was nearest to Slotin , suffered an estimated dose of 390 roentgens , and was given a 50 percent chance of survival . This caused severe radiation poisoning , loss of hair and a zero semen count . After two weeks of hospitalization and a several weeks of convalescence , he seemed to have recovered fully , and in a few months was back at work and skiing vigorously , with only a bald spot on the head to show for the experience . Two years later he fathered a healthy child , their second , a son they named Alvin Palmer . 
