Assessment of external gamma exposure and radon levels in a dwelling constructed with phosphogypsum plates

Phosphogypsum, a fertilizer industry by-product, is being worldwide stockpiled, posing environmental concerns. Since this material contains natural radionuclides in significant concentrations, its use as a building material has radiological implications. In order to confirm the feasibility of the use of a new material mainly composed by phosphogypsum, an experimental house was built, having some of its rooms entirely lined with this material. Measurements of samples of phosphogypsum plates from different origins resulted in values of 0.2 to 2.6 for the external radiation index, thus justifying a more detailed investigation. In this paper, the application of a previously developed computational model to forecast external doses indoors is described. A comprehensive radiological evaluation is being performed, including measurement of the external gamma exposure and radon concentrations in one of the rooms of the house. The results show that the annual increment in the effective dose to an inhabitant of the house will remain below the 1 mSv limit for every reasonable scenario. The radon measurements were carried out over a period of 18 months, in order to determine the long-term average levels of the indoor radon concentrations. The results obtained are below 200 Bq m(-3), the recommended investigation level for radon.