Patent Number: 043550010
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT In accordance with one embodiment and with reference to the accompanying drawings, a nuclear boiler which works on the principles of the invention mainly includes three elementary modules made and checked in the workshop, these being, namely: a container unit or block 1, a reactor unit 2 and a unit 3 which forms a swimming bath type storing unit for used nuclear fuel elements. The reactor unit 2 which is the main subject of the present invention is constituted by a casing 7 which contains, in particular, a vessel and steam generators which are not shown since they do not form a part of the present invention. The casing 7 and its contents are supported by a stand 8 with which shifting means are associated. Said means are schematically illustrated at 9 in FIG. 2 and allow the reactor unit 2 to be shifted by rolling or sliding. Here, it should be added that the stand 8 is suitably arranged and includes separate cells or compartments one of whose features is that they allow nuclear safety circuits to be installed. Further, it is important to note that said stand is used advantageously to ensure stability of the reactor 2 during operation. More precisely, the stand 8 allows even distribution of the reactor's weight on the bottom of the container unit 1 which will now be described. The container unit 1 is in the form of a rectangular module open at 1a. It has a double bottom 4 reinforced by partitions or the like 5, as well as chambers 6 which form compartments in which, in particular, boiler auxiliary operation circuits are installed. The container unit 1 may be closed by a closing part which, in accordance with the embodiment illustrated, is a unit 3 which forms a swimming bath type storing unit for used nuclear fuel. Reference 10 is a portion of the module 3 which forms the actual swimming bath and a number of cells or compartments 11 contain in particular various control and connection circuits. The prefabricated modules 1, 2 and 3 are assembled at the works or in situ as follows. The reactor unit 2 is inserted in the cavity 12 formed inside the container unit 1 and constituting the main nuclear compartment of the boiler. Then, the module 3 which, for example, forms the swimming bath type storing unit is fitted between the top wall and bottom wall of the container unit 1 so as to close said unit and to form the completely assembled boiler such as shown in FIGS. 4 and 5. The various modules will obviously be mechanically and electrically connected together as necessary. This is facilitated by providing separate compartments both in module 1 and module 3 and in the stand 8 which carries the reactor 2 as previously described. As mentioned at the beginning of the present specification, an installation in accordance with the principles of the invention can constitute a complete nuclear boiler which forms a module which can be transported to the operation site. Therefore, with reference to FIGS. 2 and 3, a method is now described by way of example for handling and transporting the boiler. The container unit or block 1 is brought on its supports or stringers 15 provided on the sides of a tank 16 which is, for example, a shipyard dock with an adjustable level and is adjacent to a loading quay 14. The reactor unit 2 and the closing unit 3 of the nuclear unit 1 are inserted successively in the cavity 12 of the nuclear unit 1. These components are placed in the container unit 1 e.g. by rolling along a railway line illustrated schematically and referenced 17. Then, by lowering the water level in the tank 16, a barge 13 is brought into said tank and under the container unit 1. This may also be done by ballasting the barge 13. Then, by unballasting the barge or raising the water level in the tank 16, the barge is raised under the container unit 1. From then on, the nuclear boiler is ready to be transported to the chosen site. It is important to note here that the handling of the nest of the modules 1,2,3 which has just been described does not require the use of cranes since the shifts of said modules to fit them together consist mainly of translations in a substantially horizontal plane. Lastly, as specified at the beginning of the specification, the modules 1,2 and 3 can advantageously be transported separately (and this may be necessary when the conditions of access to the site are difficult, i.e. when the water level is not high, for example, in which case, one barge will transport only the container unit, for example, and the reactor unit 2 and the closing unit 3 will be transported on another barge. It should be noted, by the way, that rails may be provided on said second barge so that by connecting said rails to the railway lines 17, the modules can be made to travel along them directly onto said barge to which said components are then solidly secured. Once the modules 1, 2 and 3 reach the site, they are assembled in situ by fitting them together to form a complete boiler as illustrated in FIG. 4. Therefore the boiler in accordance with the invention has a modular structure formed by several nested units whose dimensions are limited as a function of the transport means, said units being manufactured and tested at the works and being transportable in the form of an integral assembly or even separately--a considerable advantage, since the modules may be several tens of meters long and weigh thousands of tonnes, especially the container unit 1. Of course, the invention is in no way limited to the embodiment described and illustrated which is given only by way of example. The principles of the invention may thus be applied to reactors other than nuclear boilers without going beyond the scope of the invention. The invention includes all the technical equivalents of the means described, as well as the combinations thereof if they keep within the spirit of the invention and are put into application within the scope of the appended claims.