A separation fastener assembly includes a housing defining a cavity. A frangible nut is disposed in the cavity. The nut includes a plurality of nut segments. The one-piece frangible nut greatly reduces existing assembly problems and difficulties. Adjacent nut segments are interconnected at fracture lines. A bolt has an end coupled to the nut. A movable element is disposed in the housing and movable from a first position to a second position. In the first position, the nut segments are restrained from radial expansion. In the second position the nut segments are permitted to radially expand for releasing the fastener assembly.