Thin plates or foils of beryllium are sometimes used in nuclear weapon designs as the very outer layer of the plutonium pits in the primary stages of thermonuclear bombs, placed to surround the fissile material.
Tynde plader eller folier af beryllium anvendes undertiden i atomvåbendesign som de alleryderste lag af plutonium-pit'en i den primære stadier af termonukleare bomber, placeret omkring det fissile materiale.