Patent Number: 046541918
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a small portion of the wall 1 of the safety containment of a pressurized water nuclear reactor. The wall 1, that is, the safety containment, has a spherical shape and consists of construction steel of medium quality. A pressure release pipe 2 extends through the containment wall 1 into the interior 20 of the containment and has an inner end 3 in an area where its axis is disposed about parallel to the wall 1. A closure plate 4, with which the pipe 2 is closed, extends essentially normal to the wall 1. The closure plate 4 is welded to a girder beam 6 of a U-shaped mounting structure 5 having a sturdy reinforced bracket section 8 welded to the inside of the containment wall 1 so as to extend normal therefrom and an intermediate section 7 provided with a flex joint area 9, the intermediate section 7 of the U-shaped structure 5 being remote from the wall 1 so that the open area 10 of the U-shaped structure is adjacent the wall 1. From its inner ends with which the pipe 2 is welded to the girder beam 6, the pipe extends through the bracket section 8 to which it is also welded. In the area of the pipe 2, which is disposed between the girder beam 6 and the bracket section 8, the pipe is provided with at least one circumferential groove 11 providing a reduced thickness wall area so as to form a breaking point, adapted to rupture when the girder beam 6 is pulled away from the bracket section 8 as it is shown in FIG. 2. Next to the welded closure plate 4 the girder beam 6 has an opening 12 through which one threaded end section 15 of a drawbar 13 extends which is provided with counternuts 14 tightened together with predetermined free motion gap to the girder beam 6. The drawbar 13 extends chord-like with respect to the spherical containment walls and has its other end section 16 mounted to a wall bracket 18 to which it is fastened by nuts 17, the wall bracket 18 being welded to the containment wall 1. OPERATION OF THE VALVE During an increase of pressure in the safety containment beyond its predetermined design limits, the containment wall 1 begins to stretch and grow. The drawbar free motion length is so selected that containment wall growth within elastic or even within slight plastic deformation is permitted without opening of the valve but that, at about 0.5% containment wall stretch, the pipe is ruptured at the design breaking point 11 by lever action of the girder beam 6 engaged by the drawbar 13. At 2% containment wall growth the pipe walls are separated at the breaking point to such a degree that, with a pipe diameter 20 of 20 cm, an annular gap 19 with a release flow cross-section of about 200 cm.sup.2 is formed. The play at the end of the drawbar may be set as desired by adjustment of the counternuts 14. Accordingly, the point of valve opening may be adjusted in either direction as desired. With regard to their geometry and materials, the drawbar and wall breaking point area are so dimensioned and designed that the pipe ruptures at the breaking point, preferably after a containment wall growth of at least 0.5% whereas the drawbar 13 remains in an elastic stress range. cl LIST OF REFERENCE NUMERALS 1 Containment wall PA0 2 Release pipe PA0 3 Inner end PA0 4 Closure plate PA0 5 Mounting structure PA0 6 Girder beam PA0 7 Intermediate section PA0 8 Bracket section PA0 9 Flex joint area PA0 10 Open area PA0 11 Breaking point PA0 12 Opening PA0 13 Drawbar PA0 14 Counternut PA0 15 One drawbar and section PA0 16 Other drawbar and section PA0 17 Nut PA0 18 Wall bracket PA0 19 Annular gap PA0 20 Containment interior