Research On Diffusion And Deposition Characteristics Of Uranium Aerosols In The Fume Hood

Uranium, also known as an important raw material for nuclear power, is a significant strategic resource for national defense. Safety production process and healthy operating environment are essential to providing a stable and reliable supply of strategic nuclear material to the nuclear power plant and national defense. Uranium metal vacuum melting process is an advanced uranium cycle process, however, its open and radioactive operation results in countless radioactive aerosols. Those radioactive aerosols can enter the human body and will be deposited on the lung tissue, and the reactions between biological molecules and part of radioactive aerosols dissolved in the lung lead to cytotoxicity. The ?-rays from uranium isotopes has a strong internal exposure effect, so internal exposure is the main contributor of individual doses of ionizing radiation in the uranium metal vacuum melting production process.In the uranium vacuum melting production process, uranium material is processed in special fume hood or equivalent main process units of ventilation box, and the radioactive aerosols concentration level depends largely on the performance of fume hood. An experimental platform about radioactive aerosols diffusion and deposition law in the fume hood was built based on theoretical model of diffusion and deposition in the flow field, and the fume hood used in this paper is the same size as that one of uranium making plant of nuclear industry. This paper mainly studies: 1) The law of influence of point heat source temperature on escape rate and the deposition rate of the uranium aerosols in the fume hood; 2) The law of influence of velocity of open face on escape rate and the deposition rate of the uranium aerosols in the fume hood; 3) The law of influence of particle size on escape rate and the deposition rate of the uranium aerosols in the fumehood; 4) The law of influence of ventilation rate and air supply angle of air curtain on the protection performance of fume hood.The several main achievements in the research are as follow:(1) Point heat source temperature, particle size and velocity of open face were identified as the main influencing factors for the escape rate and deposition rate of radioactive aerosol in fume hood, according to the dynamics theory of aerosol migration and characteristics of uranium metal vacuum melting process, and a special experimental equipment was designed, manufactured, and assembled.(2) The model of a calculation method of escape rate and the deposition rate for radioactive aerosol in fume hood without air curtain was provided, and the effect of point heat source temperature, particle size and velocity of open face on the protection performance of the fume hood was also discussed through laboratory test and CFD numerical simulation technique. The results suggest that: 1) The experimental results are consistent with the results of CFD numerical simulation; 2) The velocity of open face has a decisive influence on escape rate and the deposition rate of the uranium aerosols in the fume hood, and the escape rate of aerosol can be significantly reduced by increasing the velocity of open face;(3) The effect of ventilation rate and air supply angle of air curtain on the protection performance of the fume hood was discussed by using CFD numerical simulation technique. The simulation results show that: 1) The protection performance of fume hood can't be improved. 2)The escape rate of aerosols increases and shows no decreasing tendency, while the velocity of open face increases.