GB1389134A - Sub-assembly for nuclear power plant - Google Patents

Abstract

1389134 Nuclear reactor core supports CLARKE CHAPMAN Ltd 17 April 1973 [4 July 1972] 31151/72 Heading G6C A nuclear reactor core support comprises leaning post assemblies 22 (Fig. 2), and a grid assembly (for supporting nuclear fuel element assemblies), supported by the shell 10 of a diagrid vessel, passages being provided in the leaning post assemblies by which coolant (e.g. liquid sodium), above the vessel can act on the fuel element assemblies in a sense opposite to that of coolant supplied from a pump whereby faces due to hydraulic pressure the fuel assemblies are counterbalanced. The shell 10 contains radial ribs 16 and chordal ribs (18) (Fig. 1, not shown), and is closed by a top plate 20. Each leaning post assembly comprises an outer cylinder 24 extending between a rib and the top plate; the lower end of each cylinder supports radial arms 26 each carrying a fuel element support cup 28. In an embodiment of leaning post assembly 22 (Fig. 4), the arms 26 extend from a lower endpiece 30 of the outer cylinder 24 and the latter contains an inner cylinder 36 whose lower endpiece 38 is spaced from member 30. An upper end-piece 44 of the inner cylinder is integral with the upper section (not shown), of the leaning post assembly. In operation, coolant is pumped into the shell 10 via inlets 12 to fill the diagrid vessel up to the top plate 20. The high pressure coolant passes through lateral slots 60 in the lower section of the leaning post assembly and then through bores 56 to the upper section of the leaning post assembly. High pressure coolant also enters each fuel element via slots in the lower end of the support cup 28 and, after passage through the element, forms part of the body of low pressure coolant above the top plate 20. By way of bores 54 and clearances 52, 49, 50 in the leaning post assembly, the low pressure coolant reaches the space between the lower end-pieces 38, 30 and thence, via bores 59 and passages in the arms 26, passes to the interior of the fuel element support cup 28 and is applied to the fuel element supported therein in a manner to counteract the upwardly-acting force arising from the pressure drop as the high pressure coolant passes through the fuel element. In a modification of the leaning post assembly required when a downwardly-acting control rod is to enter the space within inner cylinder 36, longitudinal grooves are milled externally in the surface of the inner cylinder 36 to replace the clearances aforementioned, the inner shaft 46 is dispensed with and the inner cylinder secured in an alternative manner.