In order to be fully contained, nuclear explosions at the Nevada Test Site must be buried at a depth of 650 feet for a 5 kiloton explosive 1300 feet for a 100-kiloton explosive. Even then, there are many documented cases where carefully sealed shafts ruptured and released radioactivity to the local environment. Therefore, even if an earth penetrating missile were somehow able to drill hundreds of feet into the ground and then detonate, the explosion would likely shower the surrounding region with highly radioactive dust and gas. Long-Rod Penetration Fig. Underground nuclear tests must be buried at large depths and carefully sealed in order to fully contain the explosion.
Shallower bursts produce large craters and intense local fallout.
The situation shown here is for an explosion with a 1 KT yield and the depths shown are in feet. Even a 0.1 KT burst must be buried at a depth of approximately 230 feet to be fully contained. It is straightforward to show, however, that the maximum penetration depth is severely limited if the missile casing is to remain intact. The fundamental parameter R is the ratio of the projectile ram pressure to the yield strength of the material. The target material yields, and penetration occurs, when R is greater than one.