Determination of polonium evaporation from liquid lead-bismuth eutectic by the transpiration method

Lead-bismuth eutectic (LBE) applied as coolant and spallation target causes formation of Po-210 by neutron activation of Bi-209. For licensing and safety assessment of MYRRHA knowledge about the evaporation behaviour of polonium from lead-bismuth eutectic is of high importance. In the present work evaporation of Po-210 from LBE was investigated with the transpiration method. Kinetic experiments showed evaporation close to ideal exponential release. From temperature dependent experiments an apparent Henry constant correlation was derived, showing a good agreement with one of three different correlations from literature. Flow rate dependent experiments were performed to investigate where saturated conditions can be achieved. It remains unclear if the saturated region is quite narrow. The insertions showed no influence on saturation. Evaporation of Po in presence of Pt in the LBE was investigated as noble metals were assumed to bind Po and therefore hinder the evaporation.