Patent Number: 044217145
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a partial section of the closure head 1 of a nuclear reactor pressure vessel (not shown), which is provided with a through-hole 2, shaped as stepped boreholes 3, 4 at its opposite ends. The closure consists of a ferritic material with a heat expansion coefficient of 13.times.10.sup.-6 and is provided with a plating 5 on its inner side, which extends to stepped borehole 3 of cover 1. A nozzle 6 comprised of a nonferrous base alloy of the DIN designation Ni Cr 15 Fe with a thermal expansion coefficient of 14.times.10.sup.-6 is inserted into through-hole 2 and projects at its end provided with a thread into the area of stepped borehole 3. A compensating ring 8 made of austenitic material with a thermal expansion coefficient of 17.times.10.sup.-6 is placed on contact surface 7 formed by stepped borehole 4, and nozzle 6 is braced on this ring by means of its shoulder 9. The nozzle is fastened in the cover by nut 10 engaging in the thread of support 6, which nut comes into contact with surface 11 of stepped borehole 3. With a weld seam 12 serving only for tightness purposes, nozzle 6 is connected to plating 5 with the interposing of a packing ring 13. Nut 10 consists of a ferritic material, which has the same thermal expansion coefficient as the closure material. If the distance denoted "1" between shoulder 9 and the tension coupling amounts to 80 mm in the above-named materials, then the height "h" of the compensating ring 8 must be 20 mm. An elongation of 0.336 mm is produced for the nozzle in the region of the 80-mm long distance upon heating to approximately 300.degree. C. This value is also obtained together with nut 10, projection 14, and compensating ring 8. In this way it is assured that no heat stresses occur in the region of the tension coupling. In the example of embodiment according to FIG. 2, nozzle 6 is screwed directly into the through-hole 2 provided with an inside threading. A compensating ring 8 is placed on contact surface 7, in the same way as in the embodiment example according to FIG. 1, and nozzle 6 is braced by its shoulder 9 on this ring. In this case also, the height "h" and the material of compensating ring 8 are selected in such a way that the elongation of the nozzle in the region of length "l" is equal to the elongation of projection 14 plus the height of compensating ring 8 upon a change in temperature. If a specific difference in stress is desired, then this can be accomplished by changing height "h" or the material composition of compensating ring 8. The heat stresses in the region of the tension coupling can be successfully controlled with the nozzle penetration according to the invention. The above description and drawings are illustrative of two embodiments which achieve the objects, features and advantages of the present invention, and is not intended that the present invention be limited thereto. Any modification of the present invention which comes within the spirit and scope of the following claims is considered part of the present invention.