¹²⁷Xe quantification method development and intercomparison exercise.

Area of Science:

• Nuclear chemistry
• Environmental monitoring
• Radiochemistry

Background:

• Atmospheric monitoring for fission products like xenon isotopes (131mXe, 133mXe, 133Xe, 135Xe) is vital for nuclear explosion detection.
• 127Xe, not a fission product, has been detected and can interfere with the quantification of critical fission product radioxenon isotopes.
• Interference occurs in beta-gamma coincidence detector systems, like those used by the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), due to overlapping signatures.

Purpose of the Study:

• To demonstrate the accurate quantification of 127Xe using different measurement techniques across multiple laboratories.
• To address the interference issue posed by 127Xe in the detection of nuclear explosions.
• To develop and validate methods for measuring 127Xe in atmospheric samples.

Main Methods:

• Production of 127Xe via neutron activation of enriched 126Xe, followed by purification.
• Development of quantification methods at Idaho National Laboratory using high purity germanium detectors with self-attenuation correction.
• Modification of beta-gamma coincidence counting methods at AWE, including self-attenuation corrections for xenon volume dependency.

Main Results:

• Successful production and purification of 127Xe.
• Development of distinct, yet comparable, quantification methods at different laboratories.
• Excellent agreement in gas sample activity concentration measurements between the applied methods, validating their accuracy.

Conclusions:

• Accurate quantification of 127Xe is achievable using diverse techniques, including modified beta-gamma coincidence counting and high purity germanium detection.
• Self-attenuation corrections are critical, particularly for beta-gamma coincidence methods, and show a dependency on xenon sample volume.
• The validated methods ensure reliable atmospheric monitoring by accurately accounting for 127Xe, thereby improving the specificity of nuclear explosion detection.