This paper explores the environmental hazards associated with nuclear facilities in arid regions, focusing on the rapid migration of radionuclides facilitated by flood runoff resulting from extreme rainstorms. Through a case study of a proposed nuclear facility site in China, the study developed a comprehensive model to calculate the transformation of 90 Sr and 137 Cs in flood and subsurface water during accidents. The methodology employs a combination of field tests, radionuclide adsorption tests, the SWAT model, and the HGS model to create a fully integrated model. This approach allows for the several complex couplings (radionuclide-flood runoff-subsurface water) that have not been previously examined in the reactive solute transport. The findings reveal that despite groundwater movement being relatively sluggish, 90 Sr and 137 Cs migrate downstream rapidly due to their transportation by floods, which permeate the Upper Pleistocene gravel aquifer along the route. The study underscores the importance of considering the migration of radionuclides carried by floods generated by extreme rainstorms, as it poses a significant risk that cannot be ignored.