Abstract: The rapid and accurate search of lost radioactive sources is the core technology for radioactive source locating by aerial measurement. In this paper, the advantage and disadvantages of two methods, parameter estimation and cross locating method, were analyzed. Monte Carlo simulation was used to obtain the dose rate distribution of ¹³⁷Cs point radioactive source and natural background in the model of air-ground interface. Based on the simulation data, The optimal sampling range of the parameter estimation method (the minimum distribution range of sampling points required for maximum positioning accuracy) and the optimal threshold of the cross locating method (the minimum dose rate when the positioning success rate is greater than 95%) were obtained respectively. Aiming at the problem that the parameter estimation method is time-consuming and the accuracy of cross location method is poor, based on the obtained optimal parameters, a combined location method is proposed. The method firstly uses the cross locating method to quickly approach the radiation source, and then uses the parameter estimation method for precise positioning, and tested with simulation and field experimental data. The results show that the accuracy of this combined location method is improved by 49.6% compared with the cross locating method; and the time consumption is reduced by 71.1% compared with the parameter estimation method.

Key words: location of radioactive source, parameter optimization, combined locating method, monte carlo simulation