Statistical analysis of the spatial distribution of radionuclides in soils around a coal-fired power plant in Spain

• We study the radiological impact of coal industry in a region of Spain.
• Activity of natural radionuclides and of one artificial one has been measured.
• A study of spatial distribution of them has been performed using statistical tools.
• A dose rate map in the area under study has been elaborated from the data collected.
• Annual outdoor effective dose has been estimated and compared with data available.

Coal-fired power-plants (CFPP) can be a source of contamination because the coal contains trace amounts of natural radionuclides, such as 40K and 238U, 232Th and their decay products. These radionuclides can be released as fly ash from the CFPP and deposited from the atmosphere on the nearby top soils, therefore modifying the natural radioactivity background levels, and subsequently increasing the total radioactive dose received for the nearby population. In this paper, an area of 64 km2 around the CFPP of Velilla del Río Carrión (Spain) has been studied by collecting 67 surface soil samples and measuring the activities of one artificial and six natural radionuclides by gamma spectrometry. The found results are similar to the background natural levels and ranged from 0 to 209 for 137Cs, 11 to 50 for 238U, 14 to 67 for 226Ra, 29 to 380 for 210Pb, 15 to 68 for 232Th, 17 to 78 for 224Ra, 97 to 790 for 40K (all values in Bq kg−1). Besides the classical radiochemical tools, Analysis of Variance (ANOVA), Principal Component Analysis (PCA), Hierarchical Clustering Analysis (HCA), and kriging mapping have been used to the experimental dataset, allowing us to find the existence of two different models of spatial distribution around the CFPP. The first, followed by 238U, 226Ra, 232Th, 224Ra and 40K can be assigned to ‘natural background radioactivity’, whereas the second model, followed by 210Pb and 137Cs, is based on ‘atmospheric fallout radioactivity’. The main conclusion of this work is that CFPP has not influence on the radioactivity levels measured in the studied area, with has a mean annual outdoor effective dose E = 71 ± 22 μSv, very close to the average UNSCEAR value of 70 μSv, thus confirming the almost non-existent radioactive risk posed by the presence of the CFPP.