Measurements of ²²²Rn activity in well water of the Curitiba metropolitan area (Brazil)

Considering that ²²²Rn activity concentration in well water can contribute to indoor radon concentration levels, which represent a radiation risk for the public, measurements of ²²⁶Ra and ²²²Rn activity in well water in Curitiba, Paraná State, Brazil were performed. Each water sample was submitted to four measurements for radon concentration over an interval of three days. After two months, the same samples were submitted again to ²²²Rn concentration measurements with the objective of indirectly evaluating the amount of ²²⁶Ra in them. The ²²²Rn concentration measurements were performed with an AlphaGUARD radon monitor (SAPHYMO), and the ²²⁶Ra concentration was evaluated with the decay curves of ²²²Rn. Within a few hours after extraction, about 70% of water samples from monitored wells presented ²²²Rn concentration values above the limit of 11.1 Bq/L recommended by the EPA of the United States. The obtained activity values varied between 1.6 Bq/L and 215 Bq/L for radon concentration, and radium concentrations deviated within an interval of 0.50 Bq/L and 6.8 Bq/L. The results reveal that the biggest part of ²²²Rn found in water samples originated not from soluble ²²⁶Ra compounds but from gas exhalation by the soil and rocks adjacent to the well. The results point to the necessity of mitigation procedure development for better control of global alpha radioactivity in drinking water. - Highlights: • Radon activity in well water was measured. • Radium activity in well water was measured. • Experimental results were obtained and compared with International norms and regulations