Shipping container for radioactive materials and methods of fabrication

The shipping container includes an outer container body, an inner containment vessel housing a pair of superposed product pails and a self-extinguishing fire-retardant foam insulation layer between the outer container and inner vessel. The inner vessel includes a gusseted upper flange and a lid bolted to the flange with a sealing gasket therebetween. Upper and lower dunnages are provided at the upper and lower ends of the outer container. The upper dunnage includes ceramic fiberboard panels and foam material straddled by steel sheets and additional ceramic fiberboard panel to separate the lid of the vessel and the top of the container. The top is secured to the outer container body by bolts passing through the top and internally into tapped bolt brackets along an interior wall of the outer container body. A retaining ring secures the arcuate overlying rolled edge of the top about the beaded rim of the outer container body. A reinforced plate covers the seam of the outer container underneath the retaining ring bolt for additional container integrity. Vent holes with plastic plugs which melt in response to a predetermined temperature vent the container body to preclude pressure buildup within the container body by expanding gases.