Patent Number: 
Section: description

FIG. 1 is a schematic, partial cross-sectional, illustration of a known prestressed concrete reactor vessel (PCRV) 10 for a natural circulation reactor (NCR). PCRV 10 has a concrete shell 12 which is closed at its top end 14 by a removable top head 16. Concrete shell 12 includes a substantially cylindrical inside surface 18 defining a PCRV chamber 20. A reactor core 22 and other reactor components 24 are located in PCRV chamber 20. In the past, an insulated steel liner 26 and a reactor wall cooling system (not shown in FIG. 1) are utilized in connection with PCRV 10. Particularly, inside surface 18 of PCRV 10 is lined with steel liner 26 to facilitate keeping PCRV 10 leak-tight, and an inside surface 28 of steel liner 26 is lined with a layer of insulation 30 to substantially insulate steel liner 26 from heat generated by core 22 during reactor operation. The reactor wall cooling system for cooling concrete shell 12 is configured to transport cooling fluid, e.g., water, throughout PCRV shell 12 and includes several cooling pipes embedded in concrete shell 12. The pipes extend through shell 12 adjacent steel liner 26 and are coupled to motors, pumps, valves and heat exchangers which cooperate to transport the cooling fluid through shell 12 and disperse heat within concrete shell 12. As explained above, installing the reactor wall cooling system in reactor concrete shell 12 is time consuming and tedious. In addition, and because the cooling system pipes are embedded in the concrete, inspecting and repairing the cooling system pipes is difficult. Moreover, inspecting and repairing steel liner 26 is difficult because of insulation layer 30. FIG. 2 is a schematic, partial cross-section, illustration of a prestressed concrete reactor vessel (PCRV) 40 for a natural circulation reactor in accordance with one embodiment of the present invention. PCRV 40 includes a concrete shell 42 having an outer surface 44 and an inner surface 46. A bottom head 48 and a substantially cylindrical side wall 50 define a PCRV chamber 52. A removable top head 54 is coupled to a top end 56 of concrete shell 42 and is configured to close, or seal, vessel chamber 52. An uninsulated steel liner 58 is positioned within vessel chamber 52 and is spaced from PCRV inner surface 46 to define an insulating chamber 60 between steel liner 58 and PCRV inner surface 46. Particularly, steel liner 58 includes a bottom wall 62 and a substantially cylindrical side wall 64 extending therefrom to define a core receiving chamber 66 sized to receive reactor components such as steam separators and the core. Steel liner 58 is positioned coaxially within PCRV chamber 52 so that steel liner bottom wall 62 is spaced from bottom head 48 and steel liner side wall 64 is spaced from PCRV inner surface side wall 50. A layer of insulating material 68 is positioned between steel liner 58 and PCRV inner surface 46 to substantially insulate concrete shell 42 from heat generated within the reactor core. Particularly, insulating chamber 60 is substantially filled with insulating material 68 so that insulating material 68 extends between PCRV side wall 50 and steel liner side wall 64, and between PCRV bottom head 48 and steel liner bottom wall 62. Insulating material 68 transfers loads from steel liner 58 to concrete shell 42. Particularly, insulating material 68 transfers internal loads, e.g., pressure, from steel liner 58 to concrete shell 42. In addition, insulating material 68 substantially insulates concrete shell 42 from heat generated by the reactor core. Insulating material 68 may, for example, be a High Aluminate Cement Concrete (HACC). Alternatively, insulating pressure material 68 may be fabricated from fire bricks or fire brick variations, or heat resistant concrete, or refractory castable concrete. The concrete shell of the above described reactor is substantially insulated from heat generated by the reactor core without the inner surface of the steel liner being insulated. Such shell also is maintained at a cool temperature without requiring a reactor wall cooling system. In addition, the uninsulated steel liner of the above described reactor is believed to be easier to inspect than steel liners in known large circulation nuclear reactors. From the preceding description of various embodiments of the present invention, it is evident that the objects of the invention are attained. Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is intended by way of illustration and example only and is not to be taken by way of limitation. Accordingly, the spirit and scope of the invention are to be limited only by the terms of the appended claims.