A model for continuous on-stream neutron activation analysis

A computer model for continuous on-stream neutron activation analysis is presented. The model describes a fluid sample that is continuously circulated between two tanks that respectively surround a neutron source and a shielded detector in a closed loop system. Two Monte Carlo simulation programs are developed to predict radioisotope production rate and γ-ray counting yield of the decayed atoms in the activation and detection volumes, respectively. The number of radioactive atoms that arrive at the detection tank without decay is calculated analytically in terms of the production rate, system parameters and measurement time. A comparison between the experimental results from a generic sample system and the model predictions indicates that the model is valid. The model should be useful in optimizing the system parameters for specific applications. (author)