The aim of this project is to determine the concentrations of uranium concentration in human blood in some governorates of Iraq for (workers in radiation field in ministry of science and technology and non occupational workers in radiation field) and to find the relationship between the uranium concentration with the number of working years and with the type of human gender. The nuclear reaction used as source of nuclear fission fragment is U-235 (n,f), obtain by the bombardment of U-235 with thermal neutrons from (Am- Be) source which has a flux of (5_103 n.cm-2 .s-1). The results show that the maximum uranium concentration in blood of workers in the radiation field (1.99 ppb) (male, 36 years old and 12 years working in the radiation field and living in Basrah governorate) and the minimum concentration (0.095 ppb) (male, 22 years old and 1 year working in radiation field and living in Baghdad governorate). While for non occupational workers the maximum of uranium concentration (1.84 ppb) (female, 63 years old and living in Al- Muthana governorate) and the minimum concentration (0.25 ppb) (male, 38 years old and living in Al-Ramadi governorate). Finally, it has been found that the uranium concentration in blood samples of workers in radiation field are higher than those of non occupational workers.