| 摘要 |
PURPOSE: To increase the boiling output by providing grooves which are extended in the direction perpendicular to the longitudinal axes of fuel rods on the internal side face of a fuel assembly. CONSTITUTION: When grooves N are provided on the external side face of a water channel CAN and the side face of a reinforcing wall VW, the grooves N act as 'flow strippers' and a crawling-up liquid film F coming into collision with a surface Nk perpendicular to the flow is tripped and carried by a medium flowing beside the flow F in the form of water drops. Consequently, a large amount of liquid water is introduced to fuel rods St, because the proportion of water drops in the medium increases and a large amount of water drops TR are turned to the fuel rods ST as shown by the arrow Tr and separated from the steam flowing in the direction shown by the arrow Dp. When the obstruction of the steam to the cooling of the fuel rods on the top side of the fuel assembly is prevented by preventing the formation of a harmful liquid film on the internal side wall of the fuel assembly in such a way, the amount of a coolant introduced to the fuel rods and, accordingly, the boiling output can be increased.
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