WORLDWIDE FALLOUT 39 



TABLE 2 United Kingdom Nuclear Detonations 



nation and include the yield of each device. During the course of nuclear weapons testing 

 from 1945 through 1976, it has been estimated by Harley (1975) and updated by using 

 announced nuclear tests that approximately 230 Mt of fission yield were introduced into 

 the atmosphere, which produced approximately 360 kCi of 239,240py ^^ lesser 

 amounts of other transuranic elements. 



Prior to the detonation of the first thermonuclear device (Mike) in 1952, atmospheric 

 injections were confined mainly to the troposphere, and the mass of most of the 

 transuranic isotopes was lower than about 243. In debris from the Mike, which was 

 detonated at the Enewetak Atoll on Nov. 1, 1952, transuranium elements with masses 

 through 255 were observed. The much higher neutron yield of the Mike and subsequent 

 fusion devices than that of earlier fission devices permitted very substantial multiple 

 neutron capture by uranium, which allowed production of the very heavy elements. In 

 the detonation process, multiple neutron capture by ^^*U results in the production of 

 extremely neutron-rich products, the beta decay of which produces nuclides along the 

 line of greatest stability. Table 6 shows the relative abundance of the transuranium 

 isotopes that were formed in the Mike test (Diamond etal., 1961) as well as those 

 measured in fallout debris. The isobars of significant half-Ufe are shown together with 



