First simultaneous detection of helium and tritium inside bubbles in beryllium

Area of Science:

• Materials Science
• Nuclear Engineering
• Analytical Chemistry

Background:

• Neutron irradiation of beryllium can induce transmutation reactions, forming helium (He) and tritium (³H) within the material.
• Understanding the behavior and distribution of these transmutation products is crucial for nuclear applications and material integrity.

Purpose of the Study:

• To quantitatively detect and analyze helium (He) and tritium (³H) within bubbles in neutron-irradiated beryllium.
• To investigate the spatial distribution and number density of these gases inside bubbles.
• To correlate gas behavior with bubble characteristics and surface interactions.

Main Methods:

• Utilized Electron Energy Loss Spectroscopy (EELS) to identify and quantify He and ³H.
• Collected EELS spectra from flat hexagonal bubbles in irradiated beryllium.
• Employed electron scattering cross-section and spectral intensities for quantitative analysis.
• Observed gas adhesion and potential beryllium hydride layer formation on bubble surfaces.

Main Results:

• Successfully detected distinct EELS peaks for ³H at 13.0 eV and He at 22.4 eV.
• Quantified number densities ranging from 4-15 atoms/nm³ for He and 4-10 molecules/nm³ for ³H₂.
• Observed lower gas number densities in larger bubbles.
• Noted higher tritium density at bubble inner walls, consistent with theoretical predictions.

Conclusions:

• EELS is an effective technique for the quantitative analysis of He and ³H in irradiated beryllium.
• The study provides the first direct detection and quantification of He and ³H in beryllium bubbles.
• Findings on gas distribution and surface interactions offer insights into material behavior under irradiation and validate theoretical models.