A new scientific solution for preventing the misuse of reactor-grade plutonium as nuclear explosive

Yield analyses of nuclear explosions and thermal analyses of hypothetical nuclear explosive devices (HNEDs) based on reactor-grade plutonium are examined in a common approach. Three different levels of HNED technology are defined by criteria of geometric dimensions and thermodynamic characteristics of the chemical high-explosive implosion lenses. The results show the content of Pu-238 and the heat it generates in reactor-grade plutonium to be the key parameter. Low-technology HNEDs based on reactor-grade plutonium from spent low-enriched uranium (LEU) or MOX LWR fuel with burnups of 30 GWd/t or more are technically unfeasible. For medium technology, this limit rises to approximately 55 GWd/t burnup. Special cooling applied to such HNEDs would increase these burnup limits still further. Higher Pu-238 contents in reactor-grade plutonium are required to make such HNEDs technically unfeasible. Only for high-technology HNEDs, which could only be built by Nuclear Weapon States (NWSs), the limit to the Pu-238 content of reactor-grade plutonium would rise to approximately 9%.The paper discusses scientific lower limits of alpha-particle heat power or Pu-238 contents above which reactor-grade plutonium can be considered denatured or proliferation-resistant. However, eventually such limits could only be determined by IAEA in agreement with the countries concerned.Such denatured, proliferation-resistant reactor-grade plutonium, which makes reactor-grade plutonium HNEDs technically unfeasible, can be produced by various fuel cycle strategies employing enriched reprocessed uranium (ERU) or minor actinides (MAs). An interim phase of denatured proliferation-resistant plutonium production can be envisioned. A fully proliferation-resistant civil plutonium fuel cycle will become possible later. The use of MAs creates additional proliferation problems. While americium cannot be misused for weapon purposes, neptunium may well be. The neptunium actinide, therefore, must be avoided in an appropriate strategy of a future proliferation-resistant civil nuclear fuel cycle. A fuel cycle strategy of this type is proposed.