A Modified Tritium Trick Technique for Doping Vanadium Alloys with Helium
SourceA modified tritium trick technique was used to implant three different levels of 3He in V-15Cr-5Ti (% by weight) and Vanstar-7 specimens before irradiation in the Fast Flux Test Facility (FFTF). The modifications include: (1) wrapping of the specimens with tantalum foil to minimize oxygen contamination, and (2) a 400°C decay-time treatment to prevent vanadium tritide formation and to produce a 3He bubble distribution similar to that produced during elevated temperature irradiation. Preliminary results show that both modifications were successful. However, the tritium removal step at 700°C, especially at higher helium levels, allowed large 3He bubbles to form in the grain boundaries and severely embrittled the V-15Cr-5Ti alloy. A better microstructure for simulation purposes can probably be produced by lowering the tritium removal temperature. Vanstar-7 specimens consistently absorbed about half as much tritium, and subsequently contained half as much 3He as V-15Cr-5Ti. Implanting 3He in vanadium alloys via the tritium trick offers a convenient technique to study the mechanism of helium embrittlement without irradiation and should provide a rapid screening method to help develop embrittlement-resistant vanadium alloys.