Analytical methods for the determination of 137Cs and 90Sr in ash of fuel pellets used in Italy

In this study the radiological characterization of ashes of 22 different brands of wood pellets coming from different countries and used in the regions of central Italy was carried out. 137Cs and 90Sr, were found in the samples taken into account, 134Cs resulted always below the detection limit. 137Cs activity concentration ranges from 30 to 3176 Bq kg−1 (the arithmetic mean resulted to 571 Bq kg−1); 90Sr activity concentration ranges fro154.75 Bq kg−1 to 1443.70 Bq kg−1 (the arithmetic mean resulted to 684.80 Bq kg−1). The ratio of 90Sr and 137Cs activity concentration ranged from 0.22 to 40.79 showing a high variability. 77.2% of the samples show a 90Sr activity concentration higher than that of 137Cs. The concentration factors (activity concentration in ash/activity concentration in wood pellets) resulted to 222.8 and 230.0 for 137Cs and 90Sr respectively; both radionuclides are found completely in the ashes.