Study of radionuclides decay and deposition during channel turbulent transport using a stochastic simulation method

Aiming at the inaccuracy in radiation monitoring when the air containing radionuclides is transported in a long pipe. This paper proposes a quick numerical method of simulating radioactive aerosols transport, deposition and radionuclides decay in a turbulent channel fluid by using a stochastic method. A wall-bounded turbulent fluid is adopted in the simulation, and the diameters of particles are 1 and 10 μm, the density is 1 g/cm³, the half-life of radionuclide is 10 s. The particles trajectories and instantaneous distribution are obtained by the simulation. The dimensionless deposition velocity is validated by comparing with Wood's predictions and the experienced equation for gravity settlement. During the particles transport, the detention time of particles and radioactivity after the decay in the pipe exit are multicomponent following a probability distribution. The effect of turbophoresis causes the particles accumulating in the channel-central area or near-wall area. The results show that 31% and 21% micron particles have deposited on the walls when the gravity settlement is and is not considered. When the half-life is 10s, the activity in the outlet is 21% and 10% respectively larger than the estimations obtained by the function of exponential decrease depending on the mean detention time and half-life. (author)