Patent Number: 054426677
Section: claims

1. A reactor pressure vessel for a nuclear reactor, comprising an upper part and a lower part, said upper and lower parts having an outer surface, at least said lower part having first subregions with a lesser wall thickness and second subregions with a greater wall thickness, said first subregions having said lesser wall thickness being formed by recesses in said outer surface, and said lesser wall thickness being selected for a rated operation. 2. The reactor pressure vessel according to claim 1, wherein each of said recesses has a diameter being approximately in a range of from 0.5 to 2 m. 3. The reactor pressure vessel according to claim 1, wherein said recesses have a rounded inside, in particular being dome-shaped. 4. The reactor pressure vessel according to claim 1, wherein said recessed have a dome-shaped inside. 5. The reactor pressure vessel according to claim 1, wherein said recesses have a symmetrical configuration as seen in the direction of said outer surface. 6. The reactor pressure vessel according to claim 1, wherein said upper and lower parts have an outer surface, and including a ring on said outer surface between said upper and lower parts. 7. The reactor pressure vessel according to claim 1, wherein all of said first subregions have the said size. 8. The reactor pressure vessel according to claim 1, wherein between 8 to 30 of said first subregions with said lesser wall thickness are provided in said lower part. 9. The reactor pressure vessel according to claim 1, wherein said first subregions having said lesser wall thickness are symmetrically distributed. 10. The reactor pressure vessel according to claim 1, wherein said upper part is cylindrical. 11. The reactor pressure vessel according to claim 1, wherein said first subregions having said lesser wall thickness are in said lower part and in said upper part. 12. The reactor pressure vessel according to claim 1, wherein said upper and lower parts are formed of a ferritic steel wall material, said lesser wall thickness in said first subregions is approximately 15 cm, and said greater wall thickness in said second subregion is approximately 25 cm.