| dc.description | Background: The use of natural radioactive building materials could be a health risk for both dwellers and
mining workers. Therefore, a quick and effective method to test batches of rock samples is needed. Nevertheless,
there is no reference value for maximum exhalation rates for building materials, except radiological hazard
indices that do not measure gas exhalation rates directly.
Objectives: This article investigated the correlations between Gamma Index and radon and thoron exhalation
rates, and the proportions of radon and thoron in samples. Moreover, the main objectives were to analyze the
feasibility of screening problematic samples for indoor use through a portable radiation detector (CoMo 170),
which consists of a quick analysis at very low cost, and to simulate indoor concentration of radon using the
measured exhalation rates of dimension stone slabs.
Design: Best-selling dimension stone slabs were submitted to the following assays: gamma spectrometry, radon
and thoron exhalation analysis using scintillation cell, and radioactivity measurement using a portable detector.
Univariate and multivariate statistical analyses were conducted using Statistica 13 software.
Results: The average activity concentrations measured were 971 ?? 58.6 Bq/kg of 40K, 184 ?? 9 Bq/kg of 232Th, and
74 ?? 3 Bq/kg of 226Ra. The maximum activity concentrations of 40K, 232Th, and 226Ra series were 1,734 ?? 100 Bq/kg,
2,667 ?? 109 Bq/kg, and 596 ?? 2 Bq/kg, respectively. The average exhalation rate of 222Rn was 406 ?? 20 Bq/h m2.
Conclusions: The main recommendations arising from this study are as follows: a portable radiation detector
(CoMo 170) could be used as a screening method for selected samples; Gamma Index limit value = 1 for
dimension stone slabs could be adopted when assessing radon and thoron exhalation; and the surface radon
exhalation rate should be measured as a basis of recommendation for surface treatment before sales. Finally,
thoron exhalations should be considered in radiological assessment, as 57% of the samples had higher thoron
exhalation rates than radon. | |
