Determination of gadolinium by PGNAA with a D-T neutron generator and optimization algorithm

Soluble neutron poisons are introduced to maintain criticality safety for reprocessing spent nuclear fuel (SNF). Gd is a highly effective soluble neutron poison and has been widely applied in the process, thereby rendering online monitoring of Gd solution concentrations particularly important. In this study, a Gd solution measurement setup was developed using prompt gamma neutron activation analysis technology, comprising a D-T neutron generator and a BGO detector. Experimental results demonstrated that, due to the neutron self-shielding effect, the prompt gamma rays induced by Gd exhibited a nonlinear correlation with concentration, which was corrected using Monte Carlo simulations. The minimum detectable concentration (MDC) of Gd solution for the developed setup was 1.5 mg/L. Furthermore, an optimization algorithm–based method was proposed to determine the concentration of unknown samples without relying on neutron detectors to obtain the neutron self-shielding factor. Validation with two test samples confirmed the feasibility of this approach, showing a maximum deviation of 6.7 %. These results indicate that the developed setup and method are feasible for online monitoring of Gd solutions.