Radon exhalation rate, or flux, is the rate of radon release from a source of radon. An accurate radon source term value is crucial to obtain realistic estimates from Atmospheric Dispersion Modelling codes. Common flux measurement methods provide short-term values with significant variation and underbias. PARC has developed an approved method to provide a valid annual average radon release source term. The method has been tested and validated on South African tailings dams, and has been widely used in assessing radon source terms from tailings dams, sand dumps, rock piles and cleared mining sites in South Africa, Namibia, Mozambique and Madagascar.
The radon emission rate methods are also applicable to other materials. Considerable experience is available to measure radon source term values on various materials e.g. building materials such as waste rock and phosphogypsum, and ore rock material for purposes of mine planning.