In this type of accident a reactor or other critical assembly releases far more fission power than was expected , or it becomes critical at the wrong moment in time . The series of examples of such events include one in an experimental facility in Buenos Aires , Argentina , on September 23 , 1983 ( one death ) , and during the Manhattan Project several people were irradiated ( two , Harry Daghlian and Louis Slotin , were irradiated fatally ) during " tickling the dragon 's tail " experiments . These accidents tend to lead to very high doses due to direct irradiation of the workers within the site , but due to the inverse square law the dose suffered by members of the general public tends to be very small . Also , very little environmental contamination normally occurs as a result of these accidents . For instance , at Sarov the radioactivity remained confined to within the actinide metal objects which were part of the experimental system , according to the IAEA report ( 2001 ) . Even the SL-1 accident ( meltdown of experimental nuclear reactor in Idaho , 1961 ) failed to release much radioactivity outside the building in which it occurred
SL-1
SL-1
Comparison of Chernobyl and other radioactivity releases