Method of detecting fuel failure

Purpose: To rapidly detect fuel failure after occurrence thereof in a simple constitution. Method: In a method of detecting fuel failure in the reactor core of FBR type reactors, there have been known a delayed neutron detection method, a cover gas γ-ray detection method, a precipitator method, etc. However, these methods are poor in the S/N ratio or cause time delay from the fuel failure to detection. According to the present invention, fuel failure is detected by the direct measurement of liquid sodium as the coolants while eliminating the interference of 2.25 MeV and 2.74 MeV of Na-24 radioactivated under neutron irradiation. That is, if there is no fission products due to fuel failure, a great amount of compton scattering γ-rays are present at the region lower than 2.75 MeV, but γ-rays are scarcely present at the level higher than 2.75 MeV. On the contrary, if fission products are present due to fuel failure, a great amount of γ-rays due to fission products are present at the level higher than 2.75 MeV. Accordingly, it is possible to detect the absence or presence of fuel failures by measuring only the γ-rays at the level higher than 2.8 MeV. (Kamimura, M.)