Self-absorption correction in determining the 238U activity of soil samples via 63.3 keV gamma ray using MCNP5 code

Area of Science:

• Nuclear Physics
• Environmental Science
• Analytical Chemistry

Background:

• Accurate analysis of Uranium-238 ((238)U) activity is crucial for environmental monitoring.
• The 63.3 keV gamma ray from (238)U is subject to significant self-absorption in sample materials, complicating measurements.
• Existing methods may not fully account for variations in sample properties.

Purpose of the Study:

• To develop and validate a method for correcting self-absorption of the 63.3 keV gamma ray from (238)U.
• To improve the accuracy of (238)U activity measurements in diverse soil types.
• To combine experimental data with Monte Carlo simulations for robust self-absorption correction.

Main Methods:

• Utilized a High-Purity Germanium (HPGe) detector-based gamma spectrometer.
• Employed a hybrid approach combining experimental measurements with Monte Carlo MCNP5 calculations.
• Investigated the influence of sample chemical composition, density, and geometry (cylindrical samples with variable height and density) on self-attenuation factors.

Main Results:

• Successfully developed a method for self-absorption correction of the 63.3 keV gamma ray.
• Calculated self-attenuation factors considering sample properties.
• Applied the method to grey, alluvial, and red soil types in Vietnam.

Conclusions:

• The developed method provides accurate corrections for (238)U activity measurements.
• The results demonstrated good agreement with other established analytical techniques.
• This approach enhances the reliability of (238)U activity assessment in environmental samples.