Assessment of Gamma Radiation Dose Rate from a Container with Radioactive Waste

Assessment of personnel exposure from various operations performed inside radioactive waste (RW) storage facilities is seen as an essential task under the safety assessment of such storage facilities. However, radiation scattered from the structures inside the premises of RW storage facilities is often not taken into account in the assessment of personnel exposure doses. Characteristics of the radiation field from RW containers have been calculated under a few studies. For example, the radiation fields were calculated based on some engineering approaches and the Monte Carlo method using specialized software. This paper focuses on the Monte Carlo calculations of the gamma radiation dose rate from a volumetric cylindrical source located in a RW storage facility. The study evaluates the contributions of scattered radiation from the walls, floor and ceiling of a storage premise to the absorbed dose also considering the case of a flooded floor. The paper compares the calculated radiation dose rates with those evaluated by integrating the source volume for axisymmetric geometries with no account taken of scattered radiation. The calculations show that depending on the distance from the source if no scattered radiation from all the wall, floor and ceiling structures of a storage facility is accounted for, the dose rate may be underestimated by up to two times.