Low-background gamma spectrometry for environmental radioactivity

Area of Science:

• Nuclear instrumentation
• Environmental radioactivity monitoring
• Low-background counting techniques

Background:

• Accurate measurement of low-level radioactivity is crucial for environmental monitoring.
• Existing spectrometers may have limitations in sensitivity and background noise.
• Development of advanced detection systems is needed for precise environmental analysis.

Purpose of the Study:

• To develop and characterize a novel low-background gamma-ray spectrometer.
• To assess its performance for environmental radioactivity measurements.
• To demonstrate its application in determining radium-228 in drinking water.

Main Methods:

• Utilized a 131% efficient Germanium (Ge) detector in a U-type configuration.
• Employed extensive passive shielding (6" ultrapure lead, 6" pre-WWII iron) and active muon shielding.
• Positioned the setup underground with 33m water-equivalent overburden.
• Performed low-level radium-228 determination in drinking water using a 1-step chemical procedure.

Main Results:

• Achieved a remarkably low integrated background rate of 0.068 counts/sec/100 cm³ Ge volume (50-2,700 keV).
• Reached a detection limit of 20 mBq/l (0.55 pCi/l) for radium-228 in 1L water samples within 1,000 minutes.
• The achieved detection limit meets the U.S. Environmental Protection Agency (EPA) mandated limit of 1 pCi/l.

Conclusions:

• The developed spectrometer is a highly effective reference instrument for accurate, low-level environmental radioactivity measurements.
• It demonstrates significant potential for sensitive detection of radionuclides like radium-228 in water.
• Future upgrades could further enhance detection capabilities, potentially enabling direct water analysis without chemical processing.