Patent Number: 044656530
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Description is now given with reference to FIGS. 1, 2 and 3 of a fast breeder embodying this invention in which liquid sodium is applied as a coolant. Reference numeral 10 denotes a reactor vessel containing a core 14 mounted on a support board 16. An upper plenum chamber 18 is provided above the core 14. A lower plenum chamber 20 is formed below the core 14. The upper opening of the reactor vessel 10 is covered with a shielding plug 22. An upper core structure 24 is formed below the shielding plug 22 in a state facing the upper surface of the core 14. The primary coolant flows into the reactor core 14 from the lower plenum chamber 20, is heated to a high temperature while passing through the core 14, and enters the upper plenum chamber 18. In the reactor vessel 10, a plurality of vertically extending cylindrical intermediate heat exchangers 26 are arranged substantially around the periphery of the circular core 14, with the lower end of the respective heat exchangers 26 penetrating the core support board 16. A primary coolant inlet 28 is formed at that part of the vertically extending cylindrical heat exchanger 26 which is positioned below the level of the primary coolant held in the upper plenum chamber 18. A primary coolant outlet 30 is provided at the lower end of the heat exchanger 26. Hot primary coolant drawn out of the core 14 into the upper plenum chamber 18 flows into the intermediate heat exchanger 26 at the inlet 28. In the heat exchanger 26, heat exchange takes place between the primary and secondary coolants. The primary coolant whose temperature has now fallen runs through the outlet 30 into a lower plenum chamber 32 provided in the lower part of the reactor vessel 10 which is positioned below the core support board 16. Provided above the core support board 16 is a partition wall 34 which is shaped as a whole in the annular form and whose segments substantially surround the outer half periphery of each cylindrical heat exchanger 26. A vertically extending plenum chamber 36 which is shaped substantially in annular form is provided between the partition wall 34 and the inner wall of the reactor vessel 10. The primary coolant drawn out of the intermediate heat exchanger 26 into the plenum chamber 32 below the reactor vessel passes through a port 38 (FIG. 3) formed in the reactor support board 16 into the annular plenum chamber 36. A plurality of primary coolant circulation pumps 40 are provided outside of the reactor vessel 10. The annular plenum chamber 36 is made to communicate with the suction side of the primary coolant circulation pump 40 by means of a primary coolant outlet pipe 42. The discharge side of the primary coolant circulation pump 40 and lower plenum chamber 32 communicate with each other by means of a primary coolant inlet pipe 44. The primary coolant whose temperature has fallen and which has entered the annular plenum chamber 32 is conducted to the circulation pump 40 through the outlet pipe 42 and discharged from the circulation pump 40 in a highly pressurized state. The highly pressurized primary coolant is sent to the lower plenum chamber 20 through the inlet pipe 44, and then to the core 14. With a nuclear reactor embodying this invention which is constructed as described above, the primary coolant discharged from the circulation pump 40 passes through the inlet pipe 44, and lower plenum chamber 20 into the core 14. The primary coolant which has passed through the core 14 with an increase in temperature runs into the upper plenum chamber 18, and falls in temperature due to heat exchange with the secondary coolant during passage through the intermediate heat exchanger 26. The primary coolant whose temperature has now dropped flows into the lower plenum chamber 32, and then through the annular plenum chamber 36 and outlet pipe 42 back to the circulation pump 40. The primary coolant which has traveled through the aforementioned route has covered the whole of its circulation course, and is brought to a state ready for succeeding circulation. According to the above-mentioned circulation course of the primary coolant, only the intermediate heat exchangers 26 are set in the reactor vessel 10, and the primary coolant circulation pumps 40 are disposed outside of the reactor vessel 10. Therefore, the reactor vessel 10 can be rendered appreciably compact as in the conventional loop type reactor, and can be manufactured easily. Since only the primary coolant circulation pumps 40 are installed outside of the reactor vessel 10, it is possible to reduce the length of the outlet pipe 42 and inlet pipe 44 of the primary coolant, both being located outside of the reactor tank 10. Further, these outlet and inlet pipes 42, 44 allow for the passage of only the primary coolant which has passed through the intermediate heat exchangers 26 and whose temperature has dropped, making it possible to alleviate the thermal conditions to be taken into account in designing a nuclear reactor, and consequently facilitating the design and manufacture of pipes and simplifying their entire arrangement. Further, the primary coolant circulation pumps 40 built outside of the reactor vessel 10 can be simplified in construction and installation, assuring easy maintenance and repair of said circulation pumps 40 and intermediate heat exchangers 26. The foregoing description refers to only one embodiment of this invention. It will be noted that the invention is not limited to said embodiment. For instance, the aforementioned partition wall and plenum chambers need not always be provided.