Patent Number: 042808731
Section: summary

The present invention relates to a nuclear power plant with liquid-metal cooling, in which the heat produced is given off by the nuclear reactor to primary loops and by the latter in intermediate heat exchangers to secondary loops, where the nuclear reactor may be a so-called fast sodium-cooled reactor. Such a plant is presently under construction by the corporate assignee of the instant application in Kalkar. In that installation, the components of the primary loops are disposed outside the reactor tank but within the reactor cavity and are connected to the reactor tank itself by pipes. Enlarging such a plant, which is constructed for an output of 300 MW, to an output 2000 MW leads to construction difficulties due to the increased dimensions of the individual components, which can be circumvented by a change in the construction. It is accordingly an object of the invention to overcome the hereinaforementioned shortcomings of the heretofore known devices of this general type and to provide a nuclear power plant installation with loop arrangement which meets, among other things, the following requirements, while basically retaining known components: 1. The plant should be as space-saving as possible. 2. The individual components of the primary loops should be disposed as close together as possible, so that the pipes connecting them are as short as possible. 3. In the event of a leak in the parts of the plant which carry liquid metal, the liquid metal should flow quickly to leakage collection points which are centrally disposed; in particular, the concrete of the containment of the plant should be protected against contact with the hot liquid metal in order to prevent the release of water from the concrete. 4. A clear separation of the radioactive parts of the plant from the rest of the parts should be ensured, especially in view of possible uncontrolled energy releases in the reactor itself. 5. The accessibility of the individual parts of the heat transfer system for repairs and tests during the construction of the plant, and later as well, is to be impeded as little as possible. With the foregoing and other objects in view, there is provided, in accordance with the invention, a nuclear power installation with liquid metal cooling, including a reactor cavity, a primary circulatory loop carrying heat from the reactor cavity, a secondary coolant loop, intermediate heat exchanging means for transferring heat from the primary loop to the secondary loop and means for pumping coolant through the loops, the intermediate heat exchanging means and pumping means being disposed in separately insulated and heated component tanks, portions of the loops connected to the intermediate heat exchanging means and pumping means forming lines leading into the reactor cavity in radial direction thereof and into the component tank in tangential direction thereof, the connecting lines being helically disposed within the component tanks, and the intermediate heat exchanging means are disposed inside said helix. The tanks and pipe ducts (which will be discussed hereinafter) are equipped with the well-known heat insulation and radiation shields, so that insulation of the individual parts of the heat transmission system can be dispensed with. The component tanks and pipe ducts are therefore "hot" and they are exposed to a gas which is inert vis-a-vis the liquid metal, so that no reactions between the liquid metal and the atmosphere can come about if leaks occur. The insulation and shields can be removed entirely or partially in a well known manner, which provides the accessibility of the tanks and pipe ducts. Since practically the entire heat transmission system is disposed outside the reactor cavity, the dimensions of the latter can be kept smaller, and it can surround the reactor tank relatively closely. The component tanks, in turn, are of a size which is technically realizable. The capability of the disposition of several (e.g., four) identically equal primary loops symmetrically about the nuclear reactor facilitates the construction of the plant, inasmuch as prefabricated parts can be used therefor to a large extent. In accordance with another feature of the invention, the intermediate heat exchanging means and pumping means associated with a primary loop are disposed in a common component tank. In accordance with a further feature of the invention, the intermediate heat exchanging means and pumping means associated with a primary loop are disposed in separate component tanks. While involving greater structural expense, the embodiment (employing separate tanks) has the advantage of improved accessibility of every component if the tank is open, whereby the required work can be finished faster and the expensive shutdown time can be shortened. Which of the alternatives is more advantageous for a given installation can be decided only after weighing these considerations which must be balanced according to each individual case, and after an accurate analysis of the operation has been performed. In accordance with an additional feature of the invention, there are provided pipe ducts connected from the reactor cavity to the component tanks, the connecting lines being disposed so as to pass through the pipe ducts. Furthermore, the pipe ducts and the pipes conducted in them may be elastic. Thus, the reactor tank, the component tanks and the components themselves can be anchored firmly, while the changes in length of the pipe lines, which occur due to temperature changes, are compensated due to their elastic resiliency. Additionally, the elastic parts of the pipe lines may be located inside the component tank itself; they can be accommodated there without special difficulties. Moreover, the pumps and/or the intermediate heat exchangers may be disposed in the neutron beam shadow of the reactor, whereby these important and possibly trouble-prone parts remain much more accessible for servicing and repair and, in particular, activation of the coolant in the secondary loop is prevented. For this reason the pipe lines run into the containment radially and into the component tanks tangentially. The neutron radiation which enters through the opening formed in the containment for bringing the piping through thus only strikes the curvature of the pipe line after it enters the component tank. Simultaneously, this construction facilitates the layout of the expansion loops specified above. In accordance with an added feature of the invention, there are provided inspection openings formed in at least one of the pipe ducts and component tanks, the openings being dimensioned so as to allow the insertion of work tools into the component tanks, and radiation-shielding covers adjustable for closing the openings. However, in sealing such openings, problems arise which can jeopardize the availability of the plant. In accordance with a concomitant feature of the invention, the openings are cut into the surface of the ducts and/or tanks. The openings can be made only when required by means of cutting tools (including cutting torches). Thus, the openings can be adapted as to location and size to the respective repair or inspection purpose and are closed off again securely and completely by welding-in a cover member after the work is completed. Through deposition of radioactive parts from the coolant, pipe lines and other components can radiate to such a degree even after the coolant is drained out, that work thereon is possible only by means of remotely controlled tools, and shielding may be dispensed with for a short time at most, for making an opening. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a nuclear power installation with loop arrangement, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.