Re-defining the aspects of transport safety regulations (TS-R-1) for the transport of bulk material

Abstract

Transport of radioactive material is an essential activity worldwide. Both safety and security during transport are matters of international importance. The IAEA Safety Standard (ST-R-1) has been adopted worldwide for the safe transport of radioactive materials. The problem that was addressed within the IAEA Transport Regulations is the method used to calculate the transport index (Tl) of uranium and thorium ores and concentrate. The method does not take into account some relevant parameters, which affect the dose rate like the percentage distribution of radionuclides in the material. In order to address this problem the Brazilian Nuclear Safety Directorate have developed a model (BEAMATH model) to determine transport index (Tl) as a function of the surface distance of cylindrical packages containing uranium and thorium ores or concentrate in secular equilibrium with their daughters. The major focus of this research study was, therefore to test the suitability of the BAEMATH model for the determination of transport index by comparing the Tl values calculated using BAEMATH model and calculated according to IAEA Transport Regulation (ST-R-1). In order to test the BEAMATH model, dose rate measurements were taken at 1-meter from the surface of a truck with a portable dose rate meter and small samples were collected and analyzed in the laboratory using gamma spectrometer with HPGe detector. Transport index was calculated using the measured dose rate according to IAEA Transport Regulations (ST-R-1), and the uranium and thorium

concentration in ppm from the laboratory was used to calculate Tl using BAEMATH model. The results indicate that the calculated Tl according to IAEA transport regulations (ST-R-1) for pyrite and calcine ranges from 0.3 to 0.4 respectively, and Tl calculated using BAEMATH model for pyrite and calcine ranges from 0.2 to 0.4 respectively. This study has demonstrated that the BAEMATH model predicts closely to the calculated Tl according to ST-R-1 and both Tl calculated according to ST-R-1 and BAEMATH model fall within the range specified in the IAEA transport regulations (more than zero but less than one) used for categorization of pyrite and calcine. In order to be able to conclude whether to use the BAEMATH model or not, further measurements to test the model must be done from low activity to relatively high activity bulk NORM materials transported in South Africa.