GB1465630A - Nuclear reactor fuel elements and their manufacture - Google Patents

Abstract

1465630 Fuel elements SAES GETTERS SpA 1 May 1974 [2 May 1973] 19120/74 Heading G6C A fuel element contains a non-evaporable getter material which, as the temperature of the fuel element is increased, starts to sorb active gases at a temperature lower than that at which the fuel element walls start to do so, and at a rate such as to prevent the said walls sorbing any appreciable amount of said gases, the said getter material having a sorptive capacity of at least 5 c.c.-torr./g. of CO at 20‹ C. By "non- evaporable getter material" is meant one which acts as a getter below its vaporization temperature. The fuel element (Fig. 1, not shown), comprises a hermetically sealed metallic container having walls forming a fuel-containing chamber and a plenum chamber. The getter device is placed within the plenum chamber, being separated from the end closure member by a helical spring and from the fuel by a ZrO 2 insulating pellet. Suitable getter materials are those described in Specification 1,463,538). The getter material may be housed in a container of e.g. molybdenum or graphite (Fig. 2, not shown), or be surrounded by one or more metal support rings (Fig. 5, not shown). In a further embodiment, shown in Fig. 3, a getter device 30 comprises an activated non-evaporable getter material 31 held within a metal container 32 by springs 33, 33<SP>1</SP>. One end of the container 32 is sealed by a thin metal foil 36 welded at 53 and having score lines defining an area of structural weakness which can be preferentially ruptured. The container interior 37 is either evacuated or filled with an inert gas, e.g. He at slightly above atmospheric pressure via a metal pumping stem 38 which can be pinched-off. During its manufacture, the fuel element is filled with He to 20 atmospheres pressure whereupon the foil 36 is ruptured and the getter material 31 exposed to the gases in the plenum chamber. In a still further embodiment, shown in Fig. 4, getter material 41 is held within a glass container 42 by springs 43, 43<SP>1</SP>. End 44 of container 42 is sealed by normal glass blowing techniques while the other end is a dome 45 of prestressed glass. The glass container 42 is placed within a metal holder 46 terminating at the end adjacent dome 45 in a wire mesh 47. The filling with He in this case causes the dome 45 to break into a large number of small pieces thus ensuring complete contact of the getter material 41 with the plenum chamber atmosphere.