In order to assess internal doses absorbed by an organism exposed to ionizing radiation, the MIRD organization had defined, through its schema, a key coefficient known as S-value. In this work, we have used InterDosi code to estimate S-values on a voxel-based crab phantom, which illustrates the best marine ionizing radiation pollution-indicator. In this context, three radioisotopes mainly presented in a wastewater released by nuclear power activities, namely Cs-137, Te-132 and Co-58, were taken into consideration to calculate S-values in the five main organs of a crab, namely: heart, hepatopancreas, gills, gonads and shell. InterDosi simulations have been run on 64 CPUs of the HPC-MARWAN-CNRST computing grid, each one runs 108 for uncharged particles and 1/10 of this value for charged particles. The S-value calculation has been simplified by not calculating the Specific Absorbed Fraction (SAF) for an energy E1 if it is previously calculated for an energy E0 in a condition that (E1/E0<=1.01). This simplification was applied in order to speed up the simulation as the number of SAFs required is too big. Results had shown that the Te-132 produces the most higher S-values on the crab, followed by Cs-137 and Co-58. It can be explained by the fact that the Te-132 is the most high-energy beta- emitter among the three radioisotopes. We concluded that radiological impact of crab exposure to radioactive wastewater is radio-isotope dependent. The calculation of S-values for all radio-isotopes presented in a radioactive wastewater is required for internal dose assessment.
Keywords: InterDosi; S-value; Monte-Carlo; Internal dosimetry; aquatic radiation protection