the required NEM could be supplied from existing undeclared stocks or could be newly produced at undeclared production facilities. We first discuss tools and techniques for detecting clandestine stocks of nuclear weapons or NEM, if they exist, and then turn to the problem of detecting clandestine production of weapons and NEM. In both cases, we attempt to estimate very roughly the maximum size of an undeclared stockpile or production activity that might go undetected.

TABLE 4-1 Routes to Undeclared Nuclear Weapons

Route to undeclared nuclear weapons

Source of NEM


  • Move existing weapons to a clandestine storage or deployment facility

None Required


  • Transfer of weapons from another state



  • Assemble new weapons at clandestine facility


  • Existing, undeclared stocks at clandestine storage facility

  • New, undeclared production at clandestine facility

  • Covert diversion from declared stocks or production facility

  • Transfer from another state

These highlighted routes to undeclared weapons are the principal focus of this chapter. Covert diversion of NEM from declared stocks or production facilities was considered in Chapter 3, where we concluded that the application of safeguards like those used by the International Atomic Energy Agency (IAEA) should be able to detect any significant diversion. We also do not consider here the problem of overt breakout—that is, the open diversion of NEM from declared stocks or production facilities—because this would provide timely warning that the state may be producing undeclared nuclear weapons, which is the purpose of the monitoring system. Nor do we discuss the possibility of theft or transfer of nuclear weapons or NEM from other states. We assume that any significant theft would be detected, and the transfer of weapons or NEM would only shift the problem of detecting a false declaration from one state to another (provided that all such states were subject to equivalent monitoring and safeguards arrangements).

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