Patent Number: 044217145
Section: summary

BACKGROUND The present invention relates to nuclear power plant systems and more particularly to a nozzle penetration device for a nuclear reactor pressure vessel closure head. Such a nozzle penetration is known from Swiss Pat. No. 38 37 06. The penetration, which consists of an austenitic material, is screwed into the ferritic portion of the closure. This tension coupling is subject to great stress during temperature changes due to the different coefficients of expansion. The groove provided in the region of the joint weld provides no compensation for the stresses on the screw coupling, since the differences in stress are present in this region also. There is no possibility of influencing the stresses with this design, nor for constructing e.g., a desired prestressing in the region of the tension coupling. SUMMARY OF THE INVENTION The task of influencing the heat stresses on the bearing coupling regions with a nozzle penetration of the type given above is the basis for the present invention. This task is solved according to the invention by providing a compensating ring between the shoulder of the penetration and the contact surface of the closure. The compensating ring, depending on its composition and height, permits a variation of stresses in the tension coupling area until complete equilization of stress is achieved. The device according to the invention will now be described on the basis of two examples of embodiment.