Patent Number: 053923235
Section: description

As shown in FIG. 1, a cylindrical reactor pressure vessel 1 of a nuclear reactor plant is provided with a pipe socket 2, which is welded in a known manner into the vessel wall 1'. The left-hand end of the pipe socket 2 in FIG. 1 is connected to a feed-water supply line 3, e.g. by a weld 3', whereby the internal and external diameters of the line 3 and of the end of the pipe socket 2 are substantially the same. Outside the region of this connection the pipe socket 2 is widened slightly on its inside and then passes into a cylindrical face 4, which the outer end of a protective sleeve 5 slidably abuts, which sleeve extends through the pipe socket 2 towards the interior of the vessel. During the operation of the reactor pressure vessel 1, the protective sleeve 5 is subject to temperature changes, and for this reason the term "thermal sleeve" is also used for the protective sleeve. Towards the interior of the vessel next to the cylindrical face 4 in the pipe socket 2 there is also a widened portion, which then passes into a cylindrical face 4, so that an annular gap 6 remains between the protective sleeve 5 and the pipe socket 2. The end of the protective sleeve 5 protruding into the interior of the vessel passes into a feed-water distributing ring 7 (not shown in further detail), which in the vessel 1 extends along the vessel perimeter. Close to the inner end of the pipe socket 2 the outer side of the protective sleeve 5 is provided with cams 8, which extend through the annular gap 6 and centre the protective sleeve in the socket bore. During the operation of the reactor pressure vessel 1, cold feed-water is supplied via the feed-water supply line 3 and the protective sleeve 5 to the distributing ring 7, from which the feed-water overflows into the interior of the pressure vessel. The interior of the pressure vessel is otherwise filled with hot reactor water, which is also situated in the annular gap 6. As the narrow gap between the outer end of the protective sleeve 5 and the cylindrical face 4 is not tight, cold feed-water also enters the annular gap 6. Thermal stresses, which can result in cracks in the material of the pipe socket, may occur in the pipe socket 2 by the meeting of cold and hot water in the annular gap 6. As shown in FIG. 2, between the outer end of the pipe socket 2 and the feed-water supply line 3 is inserted a pipe section 10, which is widened in its central part 10' in comparison with the internal and external diameters of line 3 and the socket end. The two ends of this widened part 10' pass into a hollow conical part 11 and 11', which are tightly connected to the line 3 and the end of the pipe socket 2 respectively, e.g. by welds 13 and 14. For reasons relating to production technology, a weld joint seam 12 is also provided between the hollow conical part 11 and the central part 10'. In the widened part 10' are disposed bellows 15, which at their left-hand end in FIG. 2 comprise a cylindrical pipe section 16, the diameter of which roughly corresponds to the internal diameter of the bellows. The left-hand end in FIG. 2 of the pipe section 16 is tightly connected to a ring 17, which is welded into the central part 10' and bridges the space between pipe section 16 and the internal diameter of the central part 10'. A pipe section 18 corresponding to the cylindrical pipe section 16 is provided at the right-hand end in FIG. 2 of the bellows 15, which extend over the pipe section 10 into the protective sleeve 5. The pipe section 18 is tightly connected on its inside to the protective sleeve 5, e.g. by welding. In this manner it is possible that the protective sleeve 5--as before--can expand in the pipe socket 2 under the affect of temperature changes and that at the same time cold feed-water is prevented from overflowing into the annular gap 6, because the bellows 15 also experience the thermal expansion, but are tightly connected to the pipe section 10 and the protective sleeve 5. For reasons relating to flow technology, in the bellows 15 is disposed a pipe 20, the external diameter of which corresponds to the internal diameter of the hollow conical part 11 in the region of the weld 13. The pipe 20 is tightly connected to the hollow conical part 11 at its tapered end and extends to the end of the cylindrical pipe section 18 of the bellows 15 situated in the protective sleeve 5. The right-hand end of the pipe 20 in FIG. 2 abuts the pipe section 18 and is connected thereto in a nonsecure manner. Thus the pipe 20 can freely expand, and therefore is also a thermal sleeve. Deviating from the described exemplified embodiment shown in FIG. 2, the pipe section 10 may have the same diameter measurements as the feed-water line 3 and pipe socket 2. In such a case the bellows 15 protrude slightly into the cross section of flow. The pipe 20, which is provided in appropriate circumstances, could then be expanded at its left-hand end in FIG. 2.