Patent Number: 041464230
Section: summary

The invention relates to a nuclear reactor having a water-cooled core, a pressure vessel of pre-stressed concrete and an inner containment vessel spaced from the pressure vessel so that an insulating gap is formed between the pressure vessel and the containment. The invention relates specifically to a water-cooled reactor of the type described, in which the pressure vessel contains both hot cooling water and steam, preferably a boiling water reactor. In a nuclear reactor of the type described it is desirable for the temperature of the concrete not to exceed about 50.degree. C. This is achieved primarily by said insulating gap which may be filled with water or with a gas. Insulation is improved if an insulating layer is applied on the inner containment. A cooling system is also arranged in the concrete pressure vessel, suitably in the form of cooling pipes in the concrete close to the inner wall of the pressure vessel. The object of the invention is to effect a reactor in which the above-mentioned inner containment is divided into two parts which are not secured to each other. The inner containment is thus more easily handled, and inspection of the containment and insulating gap is easier to perform. Furthermore, problems connected with thermal expansion of the inner containment are reduced, such as attachment of the container to the pressure vessel and the arrangement of pipes for the supply of feed water to the reactor and for the removal of steam or hot water from the reactor. The nuclear reactor according to the invention is characterized in that the containment consists of an upper part and a lower part, the adjacent parts of the upper part and the lower part being arranged to form a water-filled passage having a U-shaped cross section between the insulating gap and the inside of the reactor, and adjacent parts of the lower part and the pressure vessel being arranged to form a gas-filled lock having an inverted U-shaped cross section between the insulating gap and the inside of the reactor.