Minimum detectable activity in in situ gamma-ray spectrometry

Area of Science:

• Environmental radioactivity monitoring
• Gamma-ray spectrometry
• Radiation detection and measurement

Background:

• Environmental volume samples are typically measured using gamma-ray spectrometry to determine minimum detectable activity (A(D)).
• Existing algorithms for A(D) calculation are primarily designed for laboratory analysis of collected samples, not in situ measurements.

Purpose of the Study:

• To modify and adapt the minimum detectable activity (A(D)) algorithm for in situ gamma-ray spectrometry measurements.
• To establish a method for easily predicting A(D) values for environmental monitoring in situ.

Main Methods:

• The minimum detectable activity (A(D)) algorithm was adapted for in situ measurements at a standard 1 m height.
• A(D) values for target radionuclides were determined from in situ spectra at two different sites.
• Absorbed dose rates were calculated using soil concentrations of potassium, thorium, and uranium.

Main Results:

• A linear relationship was identified between A(D) values obtained from two disparate sites.
• The ratio of A(D) values was found to be the square root of the ratio of absorbed dose rates at 1 m height.
• Calculated absorbed dose rates using soil radionuclide concentrations agreed well with measured values.

Conclusions:

• The adapted algorithm allows for straightforward prediction of A(D) values in in situ gamma spectrometry.
• A simple experimental procedure based on the established linear relationship facilitates in situ A(D) prediction.
• The findings support accurate environmental radioactivity assessment using in situ gamma-ray spectrometry.