Abstract:Taking 8 coal mines and 13 coal-fired power plants in a certain area as research objects, specific activities of four radionuclides (238U, 232Th, 226Ra and 40K) in coal-fly ash chain were analyzed and evaluated by outdoor sampling and indoor detection. The results show that enrichment coefficients of four radionuclides in raw coal-fly ash are 2.15—3.79, which is basically consistent with concentration ratio of coal, and transfer coefficient is determined as 3.79. In fly ash-fly ash brick, enrichment coefficients of four radionuclides range from 0.65 to 1.04, which is basically the same as fly ash ratio, and transfer coefficient is determined as 0.70. No loss of radionuclides occurs during the whole process, and transfer coefficient is not affected by level of radioactivity. Radioactive level evaluation of fly ash bricks shows that eight types of fly ash bricks in this area meet the requirements of national standards and are suitable for any way (can be used as the main building except X-8). The remaining five types of fly ash bricks can only be used in buildings with no close contact with human bodies, such as exterior finishes of buildings. Supervision on production and use of such fly ash bricks should be strengthened in the follow-up. Among the 13 types of fly ash bricks in this area, the annual effective dose rate of 6 types of fly ash bricks is lower than the national recommended value, indicating that the radiation harm to human body is small, and can be used as building materials.