Abstract
During a routine inspection of radioactive sources or orphan source disposal, it is essential to effectively and rapidly estimate the activity of the radioactive source. However, this estimation may be difficult, especially when the source is shielded and the shield thickness is unknown. In this paper, a new method is developed to estimate the activity of radioactive sources under shields of unknown thickness based on the ratio of the full-energy peak count (FEPC) to the single Compton scattering count (SCSC). The proposed method is evaluated by experiments, and the results show that the proposed method can obtain a relative error of thickness of less than 7% and a relative error of source activity of less than 28%, which indicate that the method can be used to efficiently estimate the activity of radioactive sources under different shields.