Indoor radon levels and total gamma dose rates measurements in Portuguese thermal spas

In this study, an assessment of indoor radon concentration and gamma dose rates were carried out in 16 Portuguese thermal spas. Indoor gamma dose rates measurements were made using a Geiger counter (Gamma Scout – GS3) and radon concentration measurements were carried out using CR-39 detectors. The detectors were exposed for an extended period of time (in average 42 days). The results showed that gamma doses rates are generally low but, in several cases, radon concentration exceeded national as well as international standards, namely the reference level recommended by the Directive 2013/59/EURATOM (300 Bq/m3) and the threshold for protection (400 Bq/m3) from the Portuguese legislation. The annual effective doses deriving from external radiation (gamma dose rates) and indoor radon concentration showed the need to implement measures to optimize the radiation protection of the workers against ionizing radiation.