Mechanical properties of pure tungsten and tantalum irradiated by protons and neutrons at the Swiss spallation-neutron source

Abstract

In this study, a post-irradiation examination of pure tungsten (W) and tantalum (Ta) specimens irradiated at the Swiss Spallation-Neutron Source is conducted. W is used as a potential candidate for a solid spallation-target material owing to its favorable properties, namely, high neutron yield, good thermal conductivity, and low thermal-expansion coefficient. However, W also suffers from several disadvantages such as poor corrosion resistance to water coolant and irradiation embrittlement. To improve these properties, cladding technologies using Ta for W alloys have been developed. In the present study, we investigated the irradiation effects on two tungsten materials—poly-crystal W (W-Poly) and single-crystal W (W-Sin)—along with pure polycrystalline Ta. The tensile-test results revealed that W-Poly exhibited almost no ductility after irradiation of 10.2–35.0 displacement per atom (dpa). W-Sin was irradiated up to 10.2 dpa and demonstrated 6% of total elongation (TE). With regard to Ta, TE decreased based on the increase in irradiation, reaching almost zero at doses of more than 10.3 dpa. For pure Ta, grain size was one of the key parameters in investigating the irradiated-material properties.

Keywords

• Solid target
• Tungsten
• Tantalum
• Irradiation
• Tensile property
• Spallation-neutron source