Research On The Analysis Method For The Fast Measurement Of Nuclear Waste With γ Spectrum

Due to the requirement for radioactive waste management of our country, it is very necessary and hot to do some further research on the radioactive waste categories and management in order to improve the management of the radioactive waste from nuclear-industry, according to the target requirement and basic principle of radioactive waste management regulations of our country, we set up a nondestructive assay (NDA) system for detecting the radionuclide categories and their intensity.The information of the radionuclide categories and their intensity are deduced by combining the attenuation data with passive gamma-ray emission data from the sample, since the sample usually have a nonuniform distribution of radioisotopes and a heterogeneous matrix within the drum , the major metrical objects are ¹³⁷Cs,⁶⁰Co and so on, which emit much higher-energy gamma-rays, for low-density radioactive waste measurement, gamma-ray assay technique has its unique advantage that is high energy resolution, the detector assembly which consists of three high-purity germanium detectors with a drum rotary can provide a segmented gamma scan . During a typical assay the attenuation effect of gamma-rays in the sample is measured by using three external transmission sources, and then the mass of radioisotope within the sample is deduced by combining the attenuation data with passive gamma-ray emission data from the sample. When calculating the whole mass of the radioisotopes within the drum, the contributions of the areas that overlap between the neighbor segments must be deducted.The sample positioning system is a rotary stage driven by stepping motors, that allows for rotation of the sample relative to the transmission sources and detectors. The electronics rack houses the data acquisition and control computer,nuclear instrumentation modules for gamma-ray spectroscopy and stepping-motor controllers, when the density of the radioactive waste is 0.5 g/cm³, the minimum detectable activity is 100 Bq/kg for ¹³⁷Cs, 50 Bq/kg for ⁶⁰Co, and the accuracy is better than±30%, the typical measuring time is 30 minutes.