Final report on the evaporation, release and capture of Hg: FP7 SEARCH DELIVERABLE D6.5

The evaporation of mercury from dilute solutions in liquid and solid lead‐ bismuth eutectic (LBE) was studied in argon atmosphere. A dedicated setup was constructed and calibrated. Mercury present as impurity in LBE was evaporated and detected by atomic fluorescence spectroscopy. Analysis methods that could accurately simulate the experimental data were developed. Coefficients of the Henry constant temperature correlation for mercury dissolved in LBE were determined. Experiments with samples from several different batches of LBE revealed that mercury at mole fractions between 10‐6 and 10‐12 and temperatures between 150 and 350 °C evaporated from liquid LBE close to ideal behavior. Evaporation of mercury from solid LBE on the other hand was larger than that from the liquid at the same temperature. At temperatures below 105 °C, mercury evaporation from solid LBE was diffusion controlled under the conditions of the experiments. On the basis of experiments under diffusion controlled conditions, a correlation for the diffusion coefficient of Hg in solid LBE was derived. With these results, release of Hg from liquid and solid LBE can be calculated for various safety evaluations of LBE based spallation targets and accelerator driven systems. In addition, several approaches to determine the mercury concentration in LBE through evaporation measurements were developed and the results of these approaches were consistent with those obtained by neutron activation analysis. This also indicated that mercury evaporates from LBE as atomic Hg(g). It was therefore concluded that existing industrial methods to capture mercury vapor can be also applied in LBE‐based nuclear systems. A brief overview and discussion of adsorption‐based mercury capture methods currently applied in industry is presented.