Self-absorption correction for beta radioactivity measurements in water samples

Area of Science:

• Environmental Science
• Analytical Chemistry
• Nuclear Science

Background:

• Accurate determination of beta radioactivity in water samples is crucial for environmental monitoring and trend analysis.
• Self-absorption of beta particles within the sample matrix can significantly affect measurement accuracy.
• Existing methods for self-absorption correction include using external absorbers or preparing empirical calibration curves with standards.

Purpose of the Study:

• To compare the effectiveness of two self-absorption correction methods for beta radioactivity determination in water.
• To evaluate the accuracy and practicality of using external absorbers versus empirical curves with varying standard masses.
• To provide recommendations for optimal self-absorption correction strategies for specific radionuclides like 90Sr/90Y and 40K.

Main Methods:

• Method 1: Estimating the absorption coefficient assuming exponential absorption using external absorbers, and deriving a relationship with maximum beta energy.
• Method 2: Preparing empirical self-absorption curves using standards of varying mass (90Sr/90Y with sodium salts; 40K with potassium salt).
• Testing both methods on gross beta activity measurements of environmental water samples.

Main Results:

• For 90Sr/90Y, self-absorption curves prepared using standards of different mass yielded more accurate results compared to the external absorber method.
• Melting sodium nitrate for 90Sr/90Y standards is recommended due to their temporal stability and homogeneous distribution.
• For 40K, using paper absorbers of varying thickness is a more efficient alternative to preparing time-consuming self-absorption curves with varying potassium standards.

Conclusions:

• The empirical curve method using standards of different mass is superior for 90Sr/90Y self-absorption correction in water samples.
• For 40K, a simplified approach using paper absorbers offers a practical and efficient alternative for self-absorption correction.
• The findings aid in selecting the most accurate and efficient methods for beta radioactivity analysis in environmental water monitoring.