Determination of radon emanation for phosphogypsum produced in Serbia

Abstract

Phosphogypsum is a waste that is generated in the production of fertilizers and is very similar to the natural gypsum, thus its use in the construction industry is possible. It usually contains an increased concentration of 226Ra in its composition. The paper presents the results of measuring the radon emanation coefficients for phosphogypsum, natural gypsum and a mixture of natural gypsum and phosphogypsum (50%), that could be potentially used for the production of gypsum boards that are widely applied in construction. Using the method of gamma spectrometry the concentration of 226Ra in the samples was determined, while the concentration of emanated radon from the samples was measured in the specially constructed chambers of different volumes (1.5 l, 2.5 l, 4.25 l, and 30 l), using active radon monitors RAD7 (Durridge Company) and RTM1688-2 (Sarad GmbH). Radon emanation measurements were performed for about 100 cycles of 1 h, after which the emanation curve was fit and the equilibrium concentration of radon activity after one month was theoretically estimated. The effect of chamber volumes on the obtained values of the radon emanation coefficient was investigated. On the basis of the obtained emanation coefficients, it is concluded that these values are strongly dependent on the volume of the measuring chamber and that they increase with expanding the chamber volume. Therefore, it is recommended to use larger volumes of measuring chambers when determining the emanation coefficient for phosphogypsum or natural gypsum. In this way, the real conditions in rooms that are potentially constructed of such materials are better represented, while at the same time the existing effect is neglected.