| 摘要 |
PURPOSE:To relieve the generation of thermal stress in a core hanging cylinder and to improve the buckling strength of the hanging cylinder by seismic load by providing flow holes which are divided and disposed to and in multiple stages in a vertical direction to the hanging cylinder. CONSTITUTION:The cylindrical hanging cylinder 16 is suspended from a roof slab 5 provided to cap the upper aperture of a reactor pressure vessel 1 in such a manner as to enclose a mechanism 9 in the upper part of the core. The bottom end of the hanging cylinder 16 is connected to a core supporting mechanism 8. The cylinder 16 is provided and opened with the elliptical or circular flow holes 17 to two stages, upper and lower, over the entire circumference on the side face thereof. The top end of the flow holes 17 in the upper stage are so disposed as to be positioned upper than the liquid level of a coolant 7. The transient state in which the inside surface of the cylinder 16 is subjected to the temp. lower than the temp. of the outside surface is generated when the reactor is rapidly shut down by, for example, reactor scram, etc. However, the coolant 7 which is lowered in the temp. passes the flow holes 17 and arrives immediately at the outside surface of the cylinder 16 and, therefore, the temp. difference between the inside and outside of the cylinder 16 is reduced and the thermal stress arising therefrom is relieved.
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