Development and optimization of gamma spectrometry of radioactive xenon

Summary

Radioactive xenon (radioxenon) is a noble gas produced during fission reactions in nuclear reactors and during nuclear weapon tests. In reactors, elevated concentrations of radioxenon are early indicators of fuel leakage. An improved (faster or more sensitive measurement) and cost-effective quantification of radioxenon on-site would allow operators to detect more rapidly fuel leakage, whereas an improved and cost-effective quantification off-site would allow regulators to have an earlier warning to activate emergency plans. As radioxenon is the first gas that would come out, in significant quantities, of a reactor in case of fuel leakage/damage, its quantification in the environment during an emergency would support decision makers in taking protective measures for the population. In the case of nuclear weapon testing, radioxenon is an appropriate tracer to detect non-compliance of states with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Here too, an improved and cost-effective quantification of radioxenon in the atmosphere would support the verification of the CTBT.

 In this master thesis, an innovative radiation detection method will be investigated for an improved or cost-effective measurement of radioxenon. Specifically, the design of a recently developed (in-house) innovative gamma radiation detection method for radioxenon will be optimized and validated for several applications. In addition, the combination with the detection of other radiation (X-rays and betas) emitted by radioactive xenon will be explored. The master thesis will be a combination of modelling work (simulation of electron/photon transport in materials) and experimental work (detection of radiation emitted by an exempt source of radioactive xenon). It will combine physics, materials science, and engineering applied to the measurement of a naturally occurring radionuclide and an environmental pollutant. The results of the research could lead to an improved quantification of radioxenon for the protection of the public and workers.

 Research questions:

• What detection limit can be achieved for gamma spectrometry of radioactive xenon using the proposed innovative radiation detection method, and how does it compare to existing detection techniques?
• To what extent does incorporating the detection of low‑energy X‑rays from radioactive xenon isotopes improve the overall detection limit for the relevant isotopes?
• To what extent does incorporating beta‑radiation coincidence detection from radioactive xenon isotopes reduce the detection limit for the relevant isotopes?