noun
nuclear bomb shelter
A shelter designed to protect against nuclear explosions and fallout.
冷戦時代には多くの国が核シェルターを建設した。
During the Cold War, many countries built nuclear bomb shelters.
防空壕 is a more general air-raid shelter, while 核シェルター specifically refers to a shelter against nuclear attacks.
Compound of 核 (kaku, 'nuclear') and シェルター (shelter, from English).