Research Of Neutron Self-shielding Effect In Measurement Of Aqueous Solutions By PGNAA Technique

Neutron self-shielding effect is one of the most crucial factor to influence the measurement precision of prompt gamma-ray neutron activation analysis(PGNAA) technique. The neutron self-shielding, which makes the counts of elements' characteristic gamma ray increase non-linearly, brought the significant interference in the measurement of aqueous solutions using the PGNAA technique. In this paper, we proposed three correction models to correct the neutron self-shielding effect based on the physical mechanism of the reaction in the measurement with PGNAA technique. And the methods were used to correct the neutron self-shielding effect in the detection of aqueous solutions.A methodology calculation model was proposed with the neutron transport method. In this model, the geometric construction of the setup and physical reaction in the samples were simplified. Then the most important factor in the neutron self-shielding effect, which was neutron total absorption cross-section, was determined based on this method. And a new model, which was the neutron total absorption cross-section correction model, was carried out based on the neutron total absorption cross-section combined with the uniformity of the aqueous solutions. Meanwhile, the third correction model based on the internal standard method was proposed, which were using the two models combined the character of hydrogen element content, to calculate the neutron self-shielding factors in the actual measurement. These three methods were used to correct the non-linear between the counts of characteristic gamma rays and the concentrations in the cadmium and boron samples. The results showed that the prompt gamma rays of cadmium and boron increase linearly with the mass of the elements after correction. And these models can be used to correct the neutron self-shielding effect in the detection of aqueous solutions by PGNAA technique.