Mass Transfer of Ni in Liquid Li Detected by Quartz Crystal Microbalance

Liquid lithium (Li) is one of the tritium breeders of fusion reactors and the target material of advanced fusion neutron source. However, its chemical compatibility with structural materials is one of the important issues. Austenitic steels corrode due to the preferential depletion of Ni from their surface in liquid Li. However, the mass transfer behaviors of Ni in liquid Li at low temperature have been rarely studied. The purpose of the present study is to make clear the mass transfer behaviors of Ni in liquid Li by quartz crystal microbalance (QCM). The Ni electrode of the QCM unit got wet with liquid Li of approximately 5.89 × 10−2 cc at 473 K and 523 K for 600 seconds. The resonance frequency of the QCM unit changed due to the mass loss of the Ni electrode by the Ni dissolution into static liquid Li. The mass losses of Ni in liquid Li at 473 K and 523 K were obtained by Saurbrey's equation as 6.60 × 10−3 g/m2 and 1.27 × 10−2 g/m2, respectively. The diffusion coefficient of Ni in static Li at 473 K was in the range between 1.13 × 10−10 and 5.10 × 10−10 m2/s by the model evaluation based on the Fick's second law. The diffusion coefficient at 523 K was in the range between 1.90 × 10−10 and 6.87 × 10−10 m2/s.