# A New Methodological Approach for the Assessment of the \({}^{238}\)U Content in Drinking Water
## 3 Results and Discussion  
Figure 3 reports the HPGe gamma spectra acquired, for the investigated drinking water sample, with no preconcentration (a), factor of preconcentration equal to 3 (b) and to 37.5 (c).  
The 1001.03 keV gamma-ray line of \({}^{234\mathrm{m}}\)Pa appears more and more evident in the spectra, as the preconcentration of the analyzed sample increases. According to Equation (1), the activity concentration of \({}^{238}\)U, in the hypothesis of the secular radioactive equilibrium  
Figure 3: The HPGe gamma spectra acquired, for the investigated drinking water sample, with no preconcentration (**a**), factor of preconcentration equal to 3 (**b**) and 37.5 (**c**).  
between it and its daughter, was found to be not quantifiable without preconcentration, and equal to (0.76 \(\pm\) 0.22) Bq/L and (0.31 \(\pm\) 0.13) Bq/L for factors of preconcentration 3 and 37.5, respectively.  
Moreover, these results were then compared with the concentration of \({}^{238}\)U obtained through ICP-MS measurement. The mass elemental concentration for uranium turned out to be (5.6 \(\pm\) 1.1) ug/L and, according to Equation (2), it was converted in \({}^{238}\)U activity concentration, giving rise to a specific activity of (69 \(\pm\) 14) mBq/L. The comparison was therefore performed by calculating the \(z\)-score parameter, as reported in Equation (3). It was found to be not quantifiable without preconcentration, and equal to 3.13 and 1.85 for factors of preconcentration 3 and 37.5, respectively.  
On the basis of the obtained results, we can therefore affirm that the preconcentration of a drinking water sample with a factor equal to 37.5, followed by a gamma spectrometry analysis of the preconcentrated aliquot, allows us to quantify, with a high degree of accuracy (z-score < 2), the specific activity of \({}^{238}\)U.  
As a matter of fact, it is widely reported in the literature that \({}^{238}\)U in drinking water is usually quantified by means of a gamma spectrometry, under the hypothesis of secular equilibrium with its daughter \({}^{234}\)Th, using the percolation through a mixed bed ion exchange resin as a preconcentration technique, with the reduction to a final volume of 1 L starting from 80 L (preconcentration factor 80), or 2 L starting from 300 L (preconcentration factor 150) [40, 41]. In the light of this, it must be emphasized how the methodological approach reported in this article is characterized by a relatively simple preconcentration process that does not require the use of chemical procedures. In addition, it can be of great utility in commonly performed drinking water monitoring activities, in which aliquots with volumes of the order of a few liters are sampled.  
Finally, from the point of view of the radiological health risk assessment, it is important to point out that the activity concentration of \({}^{238}\)U in the analyzed drinking water sample taken as a case study is much lower than the reference value of 3 Bq/L, corresponding to an Indicative Dose of 0.1 mSv /year [42]. This last parameter, calculated in the precautionary hypothesis that the water sample contains only the radioisotope in question, that the age class considered is only the one corresponding to adults, and that the water consumption is equal to 730 L/year [43]; is set as a threshold by the regulatory limit [42]. Therefore, it is possible to exclude any radiological health risk for the population of the studied area, with reference to the drinking water consumption.