TRANS URANICS FROM NUCLEAR WEAPONS OPERATIONS 8 7 



fission process; in addition, an unknown amount became environmentally inaccessible 

 because of the circumstances under which the tests were done. However, even with these 

 limitations, certain approximations can be made. 



About 195 (Glasstone, 1962) U. S. nuclear tests have been conducted in emplacement 

 locations from which transuranic materials might have reached the environment, 

 including all atmospheric and most underwater and cratering tests.* Allowing for as many 

 nuclear tests by other countries as the United States has conducted brings us to an 

 approximate worldwide total of about 400 tests. [Carter and Moghissi (1977) reported 

 389 such tests through June 1975.] 



Some of the devices tested have been of a pure fission design. Many others, however, 

 probably reflected a variety of designs involving combinations of fission and fusion 

 processes. The transuranic material released to the environment per test certainly has 

 varied considerably through the range of tests that have been done. For this discussion I 

 have assumed that, as an order of magnitude, more than 100 Ci and less than 1000 Ci of 

 transuranic source material was residual to each test. Hence a residual of between 4x10"* 

 and 4x 10^ Ci (1 Ciof^^^Pu= 16 g) of transuranic materials might remain environmen- 

 tally available from worldwide nuclear weapons testing in the atmosphere; however, only 

 a small part of the real total may remain accessible to the human environment today. 



The nature of individual test emplacements has a considerable influence on the 

 amount of the residual transuranic material that actually becomes environmentally 

 available. Of the 195 U. S. tests (Glasstone, 1962), 60 were fired at or near the earth's 

 surface and 45 were fired atop steel towers. About 90 others were detonated in a way 

 that would make most residual material environmentally available, e.g., devices emplaced 

 on tethered balloons and those positioned by airdrop, rocket, or gun. 



The fraction of transuranic material released to the world environment from nuclear 

 tests fired very close to the surface has probably been relatively small (Glasstone and 

 Dolan, 1977). Plutonium particles in particular have a strong tendency to attach to other 

 materials; hence most of the residual plutonium from a near-surface explosion would 

 become attached to the enormous amount of earthen material disturbed by the 

 explosion. Most of these plutonium-laden earthen materials, which were in the form of 

 large particles, remained fairly close to the detonation point after the test explosion. (A 

 different but somewhat comparable situation exists with the near-surface explosions on 

 moored barges in the shallow lagoons of Bikini and Enewetak.) Part of the work that has 

 been done by the Nevada Applied Ecology Groupt (NAEG) (Dunaway and White, 1974; 

 Wliite et al., 1975; 1976; 1977) at Nevada on the behavior of this earth-entrained 

 plutonium has been aimed at defining the nature of these distributions. 



The nuclear explosives detonated on steel towers represent an intermediate situation 

 wherein relatively little surface material was disturbed and the fraction of transuranic 

 residue that became associated with earthen materials was much smaller. However, the 

 towers used in these tests furnished materials that probably influenced the behavior of 

 those transuranics. The typical tower was made of heavy structural steel with an open 



*ror this discussion, there would be no point in including the contained nuclear tests from which 

 plutonium does not become environmentally available. 



fThe Nevada Applied Ecology Group was established in 1970 within the Nevada Operations Office 

 of the U. S. Atomic Energy Commission to design a comprehensive studies program looking into 

 specific environmental problems that might already exist or that might arise in connection with 

 nuclear weapons test activities. 



