A radiation shielded vault structure includes a rigid outer structure comprising a plurality of rigid structural components that are interconnected at elongated joints to define an interior space. The structural components include a layer of lower atomic number (Z) material such as aluminum alloy and one or more layers of higher atomic number (Z) material titanium and/or tantalum. The vault structure may include radiation shield members extending along the elongated joints to provide radiation shielding at the elongated joints. The shield members comprise a higher atomic number (Z) material such as titanium or tantalum. The rigid structural components may comprise plate members that are interconnected along side edges thereof. End plates may be attached to the plate members to close off the interior space.