Monte Carlo simulation of radiation dose distribution of γ-ray density meter

As an example, the authors have calculated the radiation dose distribution near by a γ-ray density meter equipped in a 1600 type dredge ship, using Geant 4 (Monte Carlo simulation software). The most serious radiation leakage is found in the region close to the detector and it's safe for using the γ-ray density meter under normal working condition. But under some abnormal condition such as the empty pipe, the density meter will detect a huge amount of radiation. For providing a safe circumstance, additional shield should be adopted. In fact a piece of steel plate of φ50 cm x 7 cm in thickness could prevent most of escaping radiation and ensure the safety. (authors)