A Simple Relationship of Maximum Δk due to Compaction of Unmoderated Fissile Materials

A simple formulation is developed that permits a quick and accurate estimate of the maximum increase in reactivity that an unmoderated fissile system can experience if subjected to high compaction forces. The k_eff estimates from the proposed model are compared with Monte Carlo and transport theory values and indicate that for low-density fissile systems and realistic compressions, there is excellent agreement. Good agreement is achieved for denser systems up to ∼20% compression. Some practical areas of application and extension of the model are indicated in which large uniform external pressures may exist.