Direct determination of radionuclides in building materials with self-absorption correction for the 63 and 186 keV g-energy lines Magdalena Dlugosz-Lisiecka * , Martyna Ziomek Technical University of Lodz, Wr oblewskiego 15, 90-924 Lodz, Poland article info Article history: Received 20 April 2015 Accepted 18 July 2015 Available online xxx Keywords: 226 Ra radionuclide Building material Interference correction Self-absorption abstract The use of 911 keV and 129 keV g-line intensity ratio has been applied for self-absorption correction of the 63 keV 234 Th ( 238 U) and 186 keV( 226 Ra and 235 U) lines in typical building materials and soil samples. Proposed procedure allows to determine 238 U from the 234 Th line (63 keV) and 226 Ra after subtraction of 235 U interference in the 186 keV. It is important in the case of low uranium concentration and weak intensity of 235 U 143 keV g energy line, when activity of this radionuclide can be apprised on the natural constant 238 U/ 235 U ratio, only (excluding accidental anthropogenic depleted uranium deposition in the soil samples). Therefore, by this method a direct and fast determination of the 226 Ra and other important radionuclides, without one month waiting period for 226 Rae 222 Rn daughter equilibrium, is possible. The accuracy of the method has been confirmed (relative relation deviation <10%) for typical buildings materials such as: tales, bricks, concrete blocks and various type of ceramic materials. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction The recreantly published well documented epidemiological studies proved the correlation between low g ray external doses and occurrence of some kind of tumors, particularly leukemia (Pearce et al., 2013; Kendall et al., 2012; Mathews et al., 2013; Spycher et al., 2015). Therefore, one can observe grooving interest in the determination of the radionuclides in typical building ma- terials and corresponding g ray doses for inhabitants (Bou-Rabee and Bem,1996; Najam et al., 2013; Mehdizadeh et al., 2011; Amit Kumar et al., 2015; Aamidalddin et al., 2015). Particularly for the g-ray exposure from the main natural ra- dionuclides 226 Ra, 232 Th( 228 Ac) and 40 K is often expressed by index f 1 calculated according to Formula (1) (European Comission, 1999; Journal of Law, 2002). f 1 ¼ A Ra 300 þ A Th 200 þ A K 3000 < 1 (1) From the other hand the exhalation of 222 Rn from the inner walls and floors is also a main source of additional internal expo- sure of inhabitants. Therefore, the 226 Ra content in the building materials should be precisely determined to fulfill the different national requirements expressed as so called f 2 indicator of the 226 Ra content in Bq/kg (usually f 2 should be lower than 200 Bq/kg (Aamidalddin et al., 2015)). The g spectrometry method with HPGE detectors seems to be an ideal one for fast determination not only those three main con- tributors to g ray external doses but also for remaining radionu- clides in buildings materials including those of anthropogenic origin, for example e 137 Cs. However, the detection efficiencies with the self-absorption correction for low energy photons and interference correction should be taken into account for good quality analysis. Fast procedures are preferable in normal radiometric analysis. In most studies 226 Ra activity analysis is based on its two progenies 214 Pb (keV) and 214 Bi (keV) (Scholten et al., 2013). Unfortunately method needs a secular equilibrium between 226 Ra and its short living progenies, which takes about 4 weeks after sample prepa- ration and careful sealing of the beaker with measured sample. Direct 226 Ra analysis on the base of 186 keV-peak energy line ac- tivity is possible after correction for natural 235 U interference in examined material. For direct 226 Ra (186.2 keV) activity evaluation of 235 U (185.7 keV) interference seems to be a serious problem due to high emission efficiency of 235 U equal 53% in relation to 3.28% for 226 Ra. However 235 U activity concentration is usually several times lower than 226 Ra. In this study direct method of 226 Ra activity concentration and * Corresponding author. E-mail address: mdlugosz@mitr.p.lodz.pl (M. Dlugosz-Lisiecka). Contents lists available at ScienceDirect Journal of Environmental Radioactivity journal homepage: www.elsevier.com/locate/jenvrad http://dx.doi.org/10.1016/j.jenvrad.2015.07.018 0265-931X/© 2015 Elsevier Ltd. All rights reserved. Journal of Environmental Radioactivity 150 (2015) 44e48