Etch-Pit計数法による中性子線量測定

概要

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Fission fragments mark scars on such an insulator as glass or mica, when fissions take place on the surface of or inside the insulator material. Very small scars on the surface of the insulator material caused by the fission fragments can be etched by the suitable chemical treatment to form etch-pits visible under the ordinary microscope. Therefore the combination of the fissionable material and the insulator material can be used for neutron detection or neutron dosimetry.<BR>We used thin film of uranium or thorium electrodeposited on gold foil as the fissionable material and the glass or mica as the detector material of the fission fragments. The thin film of the fissionable material was kept in contact with the surface of the glass or mica. The effect of the different etching condition and the stability of the scars have been studied. It has been shown by the fission film-glass or mica combination that a good agreement exists between the expected number of fissions and the number of etch-pits. Distribution of thermal neutron flux in the reactor (UTR-B) was estimated with this system. The results of the etch-pit counting were in good agreement with those estimated with the activation method. A wide range of thermal neutron dose 10 mrem to 1000 rem may be measured with a single detector of this type with reasonable accuracy.