FAST SODIUM-COOLED REACTOR CORE STRUCTURE

摘要

1,222,930. Reactors. UNITED STATES ATOMIC ENERGY COMMISSION. 15 Dec., 1969 [22 Jan., 1969], No. 60935/69. Heading G6C. A reactor core structure for a liquid metal cooled fast reactor is made up of closely packed hexagonal fuel, blanket and reflector bundles which are held tightly together by an orificing pattern which imposes a higher internal pressure in the outer fuel bundles than in the inner fuel bundles, and which is provided with an hydraulic balancing arrangement whereby a separate unclamping arrangement for refuelling is eliminated. The core is surrounded by structural rings 14 supported by a vessel wall 15 and having their inner surfaces 16 shaped to the contour of the outside surface of the reflector bundles 13. The reflector bundles 13 surround radial blanket bundles 12 and fuel bundles 11. An inlet 17 for the coolant, e.g. sodium, is provided at the lower end of the wall 15. A support plate 18 extends across the bottom of the core and a housing 19 mounted below the plate 18 defines a plenum 20, leakage from which via an aperture 22 goes into the surrounding coolant. The lower ends of the bundles 11, 12, 13 define an inlet plenum 24 to permit coolant to flow horizontally from the inlet 17 to the various parts of the core. This is accomplished by the lower construction of the bundles 11, 12 and that of the bundles 13. In the former, the hexagonal casing extends to the lower extremity of the bundle and the sides of the casing in the region of the plenum 24 are perforated by holes 26. The lower end 25 of the casing is joined to a hexagonal bottom plate 27. In the latter, the casing terminates in the plenum 24 and a bottom plate 27SP1/SP is connected to the upper section of the bundle by a central rod 28. The fuel bundles 11 each comprise a central rod 28SP1/SP joining the bottom plate 27 with a fuel pin support member 29 attached to fuel pins 30. Each blanket bundle 12 is similarly constructed. Each reflector bundle 13 comprises a stainless steel casing penetrated by cooling passages. If desired, the lower ends of bundles 11, 12 can be constructed in a similar manner to those of bundles 13. The central rod 28 or 28SP1/SP resists in tension the upward pressure loading of the fuel pins 30 due to the equal pressures against the bottom plate 27 or 27SP1/SP and the fuel pin support member 29. The bottom plates 27, 27SP1/SP each include a flange 31 to define a space 32 beneath the bottom plate which is vented to plenum 20 via apertures 33 in plate 18. Excessive upward displacement of the bundles is prevented by a rigid hold-down grid 36 located in coolant outlet 21 and normally spaced sufficiently above the bundle handles 35 to permit differential thermal expansion. Structural rigidity in the core during operation is accomplished by orificing the outlets of the outer fuel bundles such that they have a greater internal pressure than the inner bundles.