Abstract: In order to obtain a single point continuous monitoring and sampling location of radioactive airborne effluents of nuclear facilities, a gas-solid multiphase turbulent coupling method based on the Discrete Random Walk model is proposed to solve the representative sampling location. The continuous phase is simulated with the k-epsilon turbulent model. Discrete particle model was introduced to simulate the discrete phase. A gas-solid multiphase turbulent coupling calculation method in the stack based on the DRW model is established. Flow field distribution of airborne effluents in the stack is calculated. The relationships between the cyclone Angle, air velocity, tracer gas concentration, aerosol particle concentration and pipe height are analyzed. Analysis results indicated that cyclone angle, COV of air velocity, COV of tracer gas concentration, deviation between the maximum and average tracer gas concentration gradually declined and stabilized. The COV of aerosol particle concentration met the requirements at cross section 6 and 8. The representative sampling location can be determined quickly based on computational fluid dynamics. It provides a theoretical reference for field test of single point sampling of airborne effluents.

Key words: nuclear facilities, airborne effluents, single point sampling, sampling representativeness, computational fluid dynamics