Impact of the geological substrate on the radiological content of Galician waters.

Galicia (NW of Spain) is home to a highly-fractured soil rich in (238)U minerals, being the widest radon-prone area of the Iberian Peninsula. High precipitation levels confer a rich variety and abundance of both surface and groundwaters, which are extensively used for human consumption. Nevertheless, there exists no comprehensive body of information about the impact of the high environmental radioactivity on the radiological content of Galician waters. Measurements of (222)Rn, gross alpha/beta, (226, 224)Ra and (3)H activity were undertaken over a significant range of traditional springs, waters for spas and bottling plant wells. A seasonal survey was also performed for five network water suppliers to the largest Galician cities. The main outcome of this study has been the determination of statistical correlations between the water's radiological content and different environmental factors. Water measured at bottling plants reveal radiological values exceeding the U.E. limits, however this is eliminated in the industrial bottling process before reaching the consumer. Neither significant values nor seasonal variations were obtained for network waters.

(222)Rn concentration in public secondary schools in Galicia (Spain).

In the framework of a (222)Rn screening campaign that was carried out in 58 public secondary schools in Galicia (NW Spain), the largest radon-prone area in the Iberian Peninsula, a positive correlation between indoor (222)Rn concentration and outdoor gamma exposure rate was obtained. A new approach to the data acquisition in screening surveys was tested, improving the performances of this type of study and gathering useful data for future remedial actions. Using short-period detectors (charcoal canisters) firstly, in order to detect places showing (222)Rn concentrations over 400Bqm(-3), the number of locations to be measured with long-period detectors (etched track detectors) is reduced. In this screening campaign, 34% of the schools surveyed presented at least one site exceeding the 400Bqm(-3) recommended action level established by the EU, and 15% had at least one site with (222)Rn values over 800Bqm(-3). The maximum value recorded was 2084+/-63Bqm(-3). These results are discussed and compared with data obtained in schools of several countries with similar geology. Seven schools were also studied for seasonal variations of (222)Rn activity concentration. The results were not conclusive, and no significant correlation between season and (222)Rn concentration was established. Finally, a continuous (222)Rn concentration monitor was placed in the secondary school exhibiting a mean value of the (222)Rn concentration very close to 400Bqm(-3). Maximum (222)Rn concentration values were found to occur at times when the school was unoccupied.

An approach to the subslab depressurization remedial action in a high (222)Rn concentration dwelling.

Galicia (NW Spain) is a radon-prone area in the Iberian Peninsula. Measurements were carried out at a rural dwelling, with an annual average of radon concentration over 4000 Bq m(-3) and a maximum of 9000 Bq m(-3), found during a radon screening campaign held in the Autonomous Community of Galicia. We performed a detailed study to identify the main contamination source and the behaviour of the radon concentration, in which a linear dependence with temperature was verified, once corrected for relative humidity. We used different passive methods (charcoal canisters and two types of etched track detectors) as well as a radon concentration monitor that provided continuous measurement. Subsequent to this characterization, and in order to reduce the high radon concentration, a remedial action was developed using different passive and forced ventilation methods. A modified subslab depressurization technique was found to be the most effective remedy, providing a radon concentration reduction of around 96%. This method also has the advantages of being inexpensive and reliable over time.