CHAPTER 7 RADIOACTIVITY OF CRATERS OF MULTI-MEGATON EXPLOSIONS There are a number of considerations that make a general knowledge of close-in fallout levels desirable. They include the need to rescue and evacuate people from badly damaged central areas; the need to fight fire there lest it spread into otherwise habitable areas and there destroy precious resources of people, food, and equipment; and even the possible use of the crater itself as a ready-made trash dump during subsequent cleanup. Knowledge of crater exposure levels, though poor, is sufficient to answer the question for civil-defense planning: radiation-exposure rates in and near surface-burst nuclear craters will be in the order of 10°R/hr at 1 hour,,and fallout there will be substantially complete in 20-30 minutes.’ (Actual data vary from 3000 to 40,000 R/hr.) Any such level like Ghat yen 25 ¥ 4 precludes the use of the crater and approaches to it for times wecks, even on an emergency basis.