A nuclear weapon that is exploded underground can destroy a deeply buried bunker efficiently and requires significantly less power to do so than a nuclear weapon detonated on the surface would, says a new report from the National Academies' National Research Council. However, such "earth-penetrating" nuclear weapons cannot go deep enough to avoid massive casualties at ground level, and they could still kill up to a million people or more if used in heavily populated areas, said the committee that wrote the report.
