Testing of PAV-ONE, a Permeator Against Vacuum mock-up with niobium membrane, in lithium-lead eutectic at 350 °C

Tritium extraction from lithium-lead eutectic alloy (LiPb) is one of the biggest challenges to be solved for the exploitation of the WCLL (Water Cooled Lithium-Lead) as the Breeding Blanket (BB) of EU DEMO reactor. The Permeator Against Vacuum (PAV) is one of the most promising technologies to reach this goal, but it needs a bigger amount of experimental data to demonstrate its viability and to support the scale-up towards DEMO. For this reason, an experimental campaign was performed at ENEA Brasimone in the TRIEX-II facility, where PAV-ONE, a PAV mock-up based on niobium U-tubes, was characterized in flowing LiPb. This paper describes the results obtained at a temperature of 350 °C with a hydrogen partial pressure in LiPb in the range 110–230 Pa, conditions that are relevant for the WCLL BB. Furthermore, the results at 350 °C are compared with those previously obtained at 450 °C on the same mock-up and with the same flow rate, showing a reduction in the extracted hydrogen flux of about one order of magnitude. Finally, an analytical model was set up to reproduce the experimental results of the PAV mock-up. The model results had a closer fit to experimental results when using lower bound properties. This suggests that mass transport through the PbLi and molecular recombination from the PAV surface were the rate-limiting processes.