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Some Lim itations of Safeguards 



Control of nuclear materials, both because of their monetary value 

 and for their utility to make nuclear weapons, would seem to require a 

 combination of accounting and physical controls and protection. This 

 double control is not now in practice. Safeguards systems do not 

 extend to physical protection against theft or diversion, but are 

 designed only to detect such theft or diversion. The hope for safe- 

 guards is that their detection capability will deter a would-be diverter 

 by his risk of early detection and unmasking in the world community. 

 This limitation of safeguards has important consequences. It means 

 that assuring the physical security of nuclear materials is a separate 

 responsibility of the possessing nation. 



A second limitation of safeguards is technical and statistical. Ex- 

 perience indicates that large users and producers of nuclear materials 

 can never know precisely how much materials they have ; there can be 

 no assurance of the detection of every slight diversion. Unavoidable 

 process losses and statistical errors in sampling and measurement set 

 limits on accuracy. These limitations do not mean that safeguards 

 cannot achieve a high level of effectiveness. They do mean that some 

 margin of error is inescapable which might mask some small diver- 

 sions. The diversion of substantial amounts of plutonium or highly en- 

 riched uranium-235 would probably be detected, but there remains the 

 nagging possibility that enough materials might be diverted without 

 detection to make a few nuclear weapons. The possession of a few illicit 

 weapons by a smaller nation, or possibly a non-national organization 

 which might obtain the nuclear materials on a nuclear black market, is 

 a real disadvantage of nuclear power to be weighed when considering 

 the balance of cost and benefit from a policy of promoting its world 

 use. Moreover, the higher the rate at which atomic fuel is used, re- 

 processed, and increased by breeding, the larger will be the margin 

 of uncertainty attributable to statistical error and the greater the 

 chance of undetected diversion. 



