METHOD FOR REDUCING ANNIHILATION GAMMA-RAY IN MEASUREMENT OF RADIATION

摘要

PURPOSE:To realize continuous measurement of trace nuclide, e.g. trace iodine 131, in reactor water at a nuclear power station by suppressing the influence of annihilation gamma-ray. CONSTITUTION:A main detector 1 and a sub-detector 2 for detecting the photon in radiation are arranged substantially oppositely on the opposite sides of the axis of a piping P passing the reactor water. The main detector 1 detects one photons emitted simultaneously from annihilation gamma-ray in the direction of substantially 180 deg. and the sub-detector 2 detects the other photons simultaneously. Pulses from the sub-detector 2 are counted simultaneously with pulses from the main detector 1 in reverse direction thus reducing the annihilation gamma-ray of the main detector 1.