| 摘要 |
PURPOSE:To prevent a thermal conducting pipe at an inner circumference of a bundle of thermal conducting pipes from being cooled by a secondary fluid of low temperature flowing in a down-comer and reduce an axial stress of the thermal conducting pipes by a method wherein a pressurized gas is supplied between an inner shroud and the down-comer to form a thermal insulated gas layer. CONSTITUTION:Argon gas for use in thermal shielding operation is guided to a compressor 32 through an argon gas supplying pipe 33, then pressurized and passed through a check valve 31 and a communication pipe 30 and is fed into a surge tank 27, further passed through the communication pipe 25 and a check valve 24 and enters between the down-comer 7 and the inner shroud 11 through a pressurized gas supplying nozzle 18 arranged at a part projected above the upper end plate 4 of the inner shroud 11, pushes up the liquid surface of the primary fluid to form a thermal insulating gas layer 23. The check valve 24 is normally opened during an operation and it is closed in a special case such as the primary fluid is filled and the like. The vent nozzle 17, bent pipes 19 and 22 connected to the bent nozzle and the check valve 21 are applied for removing argon in the outer barrel 1 when the primary fluid is to be filled and the check valve 21 is opened only when the primary fluid is filled.
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