| 摘要 |
PURPOSE:To detect neutron without fail, not overlapping the leak current caused by the fall of insulation resistance of an insulating material by reducing the leak current of an inside insulator under a high temperature of an ionization chamber type neutron detector provided in a reactor and by measuring the real ionization current. CONSTITUTION:In the outside electroconductor 14 of a guide cable C are arranged tubular intermediate conductor 12 and central conductor 11 through the intermediary of an insulating inorganic material 15. Meanwhile, the anode 1 and the cathode 2 of the ionization chamber D for detecting neutron supported at upper and lower positions by an insulating inorganic material 5 are insulated by the supporting body 5 made of an inorganic material, while in the supporting body 5 is provided a circular conductor 6 insulated from the electrodes 1 and 2. And, the case 13 of the ionization chamber D is insulated from the cathode 7 by an insulatihg guard 7 made of an insulating inorganic material, while the conductor 6 and the conductor 12 the latter of which is located in the cable C are connected by a short-circuit conductor 10 and a connecting conductor 9, the anode 6 and the conductor 11 are connected by a connecting conductor 8, the cathode 2 is connected to the case 13 through the intermediary of an earthing conductor 17, and inside of the cathode 2 a neutron conversion material 3 is attached.
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