A practical approach to determining soil-sample detection efficiency in field gamma-ray spectroscopy.

Area of Science:

• Nuclear Geophysics
• Environmental Monitoring
• Analytical Chemistry

Background:

• Gamma spectroscopy is vital for measuring radionuclide activity in soil for various applications, including Comprehensive Nuclear-Test-Ban Treaty (CTBT) on-site inspections.
• Accurate isotopic activity extraction requires understanding detector system absolute efficiency, which depends on sample geometry, elemental composition, and density.
• Field measurements for CTBT inspections necessitate rapid sample processing, often prioritizing speed over absolute accuracy.

Purpose of the Study:

• To develop and validate a semi-empirical approach for determining detector efficiency in soil samples.
• To provide an easy-to-implement method for field radionuclide analysis suitable for rapid on-site inspections.
• To address the challenge of efficiency variations due to differing soil densities in field measurements.

Main Methods:

• A semi-empirical method was developed utilizing a calibrated standard.
• A correction factor was introduced, dependent solely on the relative density differences between the soil sample and the standard.
• The approach was demonstrated and validated through field measurements.

Main Results:

• The semi-empirical method provides a practical approach to estimating detector efficiency for field soil samples.
• The density-dependent correction effectively accounts for variations in soil matrix properties.
• Field validation confirmed the approach's utility for rapid radionuclide assessment.

Conclusions:

• The presented semi-empirical method offers a viable solution for efficient radionuclide activity measurements in soil during field operations.
• This approach balances the need for speed in on-site inspections with reasonable accuracy by focusing on density variations.
• The method enhances the applicability of gamma spectroscopy for rapid environmental and treaty verification analyses.