Patent GB-1403338-A (GB)
Title: Flasks for the confinement and transport of radioactive materials
IPC: G21F9/36
Filed: 1973-11-12
Abstract: 1403338 Containers for radioactive materials ROBATEL SLPI 12 Nov 1973 [28 Nov 1972] 52339/73 Heading B8C [Also in Division B4] A flask for enclosing and transporting radioactive materials comprises a container 1 which is surrounded by an anti-radiation, heat-conducting, shield 2, made, e.g. of lead, and spaced internally from a protective metal jacket 3 to form an annular space which accommodates a heat protection device 4 for simultaneously allowing heat emitted by radioactive material in the container 1 to be discharged and the said shield 2 to be insulated against externally generated heat, the heat protection device comprising internal and external concentric rows of metal vanes orientated to extend radially the internal and external vanes being in good heat-conducting relation to the shield and metal jacket respectively with the spaces between the vanes of the rows being filled with endothermic insulating material 8. As shown, the heatprotective device includes an external ring of profiled copper sections 5 which are of U crosssectional shape, extend over the entire height of the flask and are joined together, e.g. by welding at 5, so that the adjacent flanges of the sections 5 define vanes which are orientated radially towards the centre of the container. The web portions of the sections 5 are perforated at 5a. The device 4 also includes a second internal ring of angle profiles 6 which are preferably made of copper and which are joined to each other, at 6, so that their wings project radially outwardly between the web portions of the sections 5. The external and internal rings 5, 6 respectively are wedged together by grooved plates 7, 7 of high heat insulation material, such as wood, the spaces between the vanes of the two rings being filled with masses 8 of material of an endothermic nature. The rings 5, 6 are sealed in place by means of internal and external layers of good heat-conducting material, e.g. a composition of metal billets 50%, cast cement 33%, and reinforced plaster, the whole being mixed with 25% of water relative to the volume of dry mixture. In a modification, Fig. 3 (not shown), the shield (2) is lined with a protective neutron screen (10) the angle profiles (6) being provided with very long radial wings to define a space for suitable material between the heat protection device 4 and the outer-radiation sleeve 2. Examples of suitable neutron-screen compositions are given. The wedges, or rods, 7 ensure that heat, emitted by the radio-active material in the container 1 is discharged radially to the outer jacket 3 through the massess 8 of endothermic material the external and internal rings 5, 6, Fig. 1, providing large heat exchange surfaces and the circumferential thickness of each mass being low to provide good heat-transmission characteristics. If the packaging becomes surrounded by fire heat passes through the jacket 3 and the layer 9 to the external ring 5 the heat of which causes the water contained in the endothermic mass 8 to vaporize so that the angle profiles 6 are only heated to a moderate degree, the steam escaping through the orifices 5a, which are normally closed by fusible stoppers 3a. The endothermic material may consist either of calcium sulphate or, of a mixture formed by a suspension of aluminium trihydrate and iron, or mild steel powder in water.