Radionuclides presence in the marine ecosystem can be adversely affect human health when it enters the food chain as seafood (crab). This study is simulating the radionuclides released from a proposed site of cooling water system of nuclear power plant such as uranium (233U), (238U), radium-226 (226Ra), Cesium (137Cs) in marine biota crustacean crab, which has the ability to acclimated in high temperature in outlet cooling water system of a certain nuclear power plant, and that had occurred by using the modeling tool Res-rad biota code version (1.8), the results showed that the biological concentration guidelines (BCGs) limits of selected radionuclides are complying of the recommended BCGs limits and on the other hand, the radioactivity concentrations of Ra-226 in crab tissue is higher than radioactivity concentration of Ra-226 concentration in riparian animal while in case of Cs-137 radioactivity concentration in tissue was lower in crab than in riparian animal while crab has higher values of U-233 and U-238 radioactivity concentration in tissue than U-233 and U-238 in riparian animal, this indicates that the concentration of radionuclides inside the tissue of the selected animal depend on the type of animal . Carb also can be used as bio-indicator in cooling water system as its ability of acclimated of the increasing of temperature and salinity in marine water cooling water system.