the limiter body escape for foundations of fuel elements of nuclear reactors

摘要

1463532 Nuclear reactors SOC GENERALE DE CONSTRUCTIONS ELECTRIQUES ET MECANIQUES ALSTHOM 20 March 1974 [22 March 1973] 12474/74 Heading G6C In a nuclear reactor cooled by a liquid, fuel elements are carried by a support plate which has recesses each accommodating the foot of a respective fuel element, the foot defining an internal flow passage for the liquid and having a region of reduced cross-sectional flow area, this region being in communication with the space between the foot and the wall of the associated recess at a position downstream of a labyrinth seal acting between the foot and the wall. Thus, any leakage coolant in the space can enter the foot by virtue of the reduced static pressure in the region of reduced flow area. In one embodiment (Fig. 1) the foot 3 is centred in the recess 2 of support plate 1 by partspherical protuberances 5; intermediate its length, the foot 3 affords seals 8, 13 for reducing leakage flow in the space 12. Downstream of the seal 8, orifices 11 connect the space 12 with the flow channel within the foot 3 in the region of a narrowed portion 10 of the channel. By conducting leakage flow from space 12 into the flow channel in the foot, leakage flow past the protuberances 5 is minimized. Pressure in space 12 is maintained higher than in space 15 above support plate 1 so as to preclude reverse leakage past protuberances 5. The effects of this pressure differential are minimized by the further seal 13. In a second embodiment (Fig. 2) the foot is centred by means of an annular rib 16 which also acts as a seal; the further labyrinth seal is dispensed with. In a third embodiment (not shown), similar to that of Fig. 2, the further labyrinth seal, such as is provided in the embodiment of Fig. 1, is included. In a fourth embodiment (Fig. 4) the crosssectional flow area of the channel within the foot is reduced by means of an internal structure comprising diaphragms 18. The orifices 11 are provided in the vicinity of one such diaphragm. Levitation of the fuel element by the coolant pressure is minimized by providing for lateral entry of coolant to the foot via apertures 14, 19.