Journal of Radiation Safety and Measurement

Journal of Radiation Safety and Measurement

Investigation of the effect of environmental chemical conditions (pH) and time on the gamma radiation attenuation coefficient of rocks

Document Type : Original Article

Authors
Sahand Golmohammadi 1
Majid Noorian-Bidgoli 1
Ahmad Ramezani Moghaddam-Arani 2
1 Department of Mining Engineering, Faculty of Engineering, University of Kashan, Iran
2 Faculty of Physics, University of Kashan, Kashan, Iran
10.22052/rsm.2025.257296.1144
Abstract
Rocks, as natural barriers, play a crucial role in reducing the spread of radiation in radioactive waste disposal structures as well as in residential and office buildings. Therefore, the long-term stability of their shielding performance against variable environmental chemical conditions is of great importance. In this study, the effect of environmental chemical conditions—including different pH values (3, 4, 6, 9, and 10) and solution–sample contact time up to 24 months—on the mass attenuation coefficient of gamma rays in four types of natural stones (granite, travertine, magnetite, and hornblende) was investigated. For this purpose, three complementary approaches were employed: experimental testing using a Geiger–Müller detector, Monte Carlo simulations with the MCNPX code, and reference data from the XCOM database. First, the attenuation coefficient was determined under dry conditions, and then the samples were immersed in solutions of different pH values. The results showed that magnetite, with a mass attenuation coefficient of about 0.062 cm²/g, exhibited high shielding efficiency due to its high density and iron content (72%), but in acidic conditions (pH = 3) this coefficient decreased by up to 20%. Granite demonstrated the highest stability, with less than 10% variation across the examined pH range, making it a suitable option for deep disposal structures. In contrast, travertine exhibited a 30% reduction in acidic environments due to calcite dissolution, and hornblende showed a 15% decrease in alkaline conditions (pH = 10) due to silicate network degradation. Moreover, the contact time with solutions had a nonlinear and significant effect on reducing the shielding capacity of the rocks. The strong agreement between the results obtained from different methods (with less than 5% discrepancy) confirms the accuracy and reliability of the findings for the safe design of high-level radioactive waste disposal systems.
Keywords
Mass attenuation coefficient
Gamma ray
Natural rocks
Environmental pH
Time
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