Investigation of the vacuum pump effect of free flowing liquid lead-bismuth eutectic

Previous thermal hydraulic experiments with flowing lead bismuth eutectic (LBE) in the MYRRHA/XT-ADS windowless spallation target mock-up installed at the THEADES loop at the Karlsruher Institut für Technologie have shown that the LBE flow in the target mock-up behaves as a vacuum pump. An experimental setup is built and tested at the THEADES loop for quantification of this effect. In this paper, experimental evidence shows that the vacuum effect of flowing LBE at 200 °C, under MYRRHA like geometry and nominal LBE flow conditions, leads to an equivalent vacuum pumping speed for nitrogen gas of the order of 1 l/s. This is sufficient to reduce the vacuum pressure in the target zone below 10−3 mbar.