Gamma radiation protection factor of building materials–Validation of wall reflections from measurements

774-777The gamma radiation (INR and fallout radiations using 60Co and 137Cs sources, respectively) protection factors for 150 cm of soil (density=1.5 g/cc) followed by 21.5 cm specially prepared concrete (density=2.7 g/cc) have been estimated. Since the measurements are not amenable for such large thickness due to significant contributions from the scattered radiation, experiments are carried out for varying thickness and results are corroborated by Monte Carlo calculations. After ascertaining the calculated accuracy, the protection factors are deduced by Monte Carlo calculations. Simulations could reasonably predict the measurements within a factor of 2 for all the cases measured. It is inferred from the simulations that the dose contributions due to reflected radiations from the wall are significant when the material thickness exceeds 45.5 cm soil plus 21.5 cm concrete. Further, materials have been evaluated against fast neutrons using 252Cf source

Radiological safety aspects in Californium-252 source transfer operation

798-801The methodology, radiological safety planning and technical experiences gained during the transfer of 1 mg of 252Cf neutron source from transport container to exposure facility have been reported. Hot mockups with dummy sources and radiation safety planning in advance have been observed as the main contributing factor in personal dose reduction and to increase the confidence level in radioactive source transfer in open condition. The doses received by the personnel during this procedure are in the range 0.15-0.30 mSv, which are well within the planned dose limit during operation (5 mSv). No accidental or emergency situation had arisen during the course of this task. Before any new high strength source expected to arrive in any institution, a full-scale mockup should be performed to ensure all members of the work team to understand their parts in the operation. Minimum possible persons should be involved in source transfer. Too many minds at a time should not be applied in such a hazardous operation. There should be only one supervisor at the site and no one except the supervisor should be allowed to give instructions and suggestions during the source loading or transfer procedure. Only expert and experienced radiation safety personnel with high confidence level should undertake such operations. All technical aspects and challenges faced during the source transfer have been highlighted