Transportation vessel for spent nuclear fuel - has heat shield protecting contents from external fire by bulging bimetal plate

摘要

The container comprises a bimetal plate fitted to the external surface of the container. This bimetal plate is composed of two metal plates possessing different coeffts. of thermal expansion; the outer plate has a larger coefft. of expansion than the inner plate and both the plates are firmly connected together at their edges and fixed to the outer face of the container. The surface of the bimetal plate facing inwards towards the container and the external surface of the container itself are finished to a high polish and are in intimate thermally conducting contact. There may also be a further metal plate between the bimetal plate and the outer face of the container; this plate has a high polish on the side facing away from the container. If the container is subjected to an external fire, the outer bimetal plate immediately buckles outwards and creates a void (virtually a vacuum) between it and the inner plate or surface of the container. Since the two surfaces of this void are highly polished, very little radiation of heat across the void takes place and the contents of the container are largely protected from the external heat.