Mass spectrometric study of the interactions between nitrogen cover gas and lead bismuth eutectic alloy

Abstract

The composition of the cover gas above liquid lead–bismuth eutectic (LBE) is studied in nitrogen and argon atmospheres to evaluate the feasibility of using nitrogen as main cover gas in LBE cooled nuclear systems. A mass spectrometer is coupled to a reactor vessel setup to study online the speciation from contacting different cover gas environments with LBE. The experiments are performed in representative conditions for MYRRHA and reveal that little interactions occur between nitrogen and LBE in a temperature range between 200 and 450 °C. NO and NH3 are the only N-containing species detected in amounts similar to those of the reference measurements. Using mass spectrometry (MS), a clear and fast dissolution of O2 from the cover gas into the LBE is observed upon contacting N2 enriched with oxygen. Changes in the LBE-cover gas interface morphology could be linked to the observed evolution of the oxygen content in the gas exit stream. Thermodynamic calculations are performed to serve as guidance for the experimental campaign and the species formed in the chemical equilibria calculations are in line with the experimental results.