[en] An 18 sided hull approximately 4 metres in diameter formed in prefabricated watertight sections from GRP has been designed for burying underground to withstand an overpressure of 12P.S.I above normal atmospheric pressure for human protection against a nuclear explosion and resultant radioactivity. The pre-fabricated sections are so designed to be stacked together prior to assembling and the assembled hulls can also be stacked together both vertically and horizontally in a honeycomb formation to form a multiple chamber. (author)