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The solubility of oxygen in liquid lead bismuth eutectic (LBE) was determined by using electrochemical methods. The oxygen partial pressure in oxygen saturated LBE was measured from 475 to 724 K by using an oxygen sensor comprised of yttria partially stabilized zirconia and air/LSM (Lanthanum strontium manganite) reference electrode. Sieverts' constant of the dissolved oxygen in LBE was measured from 598 to 748 K by coulometric titration method using the oxygen sensor. The measured oxygen partial pressure in oxygen saturated LBE (P O 2 (L B E−PbO) in bar) and Sieverts' constant of dissolved oxygen in LBE (k for a 1 wt% standard state) are given by log P O 2 (L B E−PbO) = 11.52 − 22996/T (475-724 K), log k = 3.12 − 7072/T (598-748 K) respectively. Combining the measured data, the oxygen solubility in LBE (C O,S in wt%) was derived and is given by log C O,S = 2.64 − 4426/T (598-724 K).

a Liquid lead-bismuth eutectic (LBE) is an important candidate to become the primary coolant of future, generation IV, nuclear fast reactors and Accelerator Driven System (ADS) concepts. One of the main challenges with the use of LBE as a coolant is to avoid its oxidation which results in solid lead oxide (PbO) precipitation. The chemical equilibria governing PbO formation are well understood. However, insufficient kinetic information is currently available for the development of LBE-based nuclear technology. Here, we report the results of experiments in which the nucleation, growth and dissolution of PbO in LBE during temperature cycling are measured by monitoring dissolved oxygen using potentiometric oxygen sensors. The metastable region, above which PbO nucleation can occur, has been determined under conditions relevant for the operation of LBE cooled nuclear systems and was found to be independent of setup geometry and thus thought to be widely applicable. A kinetic model to describe formation and dissolution of PbO particles in LBE is proposed, based on Classical Nucleation Theory (CNT) combined with mass transfer limited growth and dissolution. This model can accurately predict the experimentally observed changes in oxygen concentration due to nucleation, growth and dissolution of PbO, using the effective interfacial energy of a PbO nucleus in LBE as a fitting parameter.The results are invaluable to evaluate the consequences of oxygen ingress in LBE cooled nuclear systems under normal operating and accidental conditions and form the basis for the development of cold trap technology to avoid PbO formation in the primary reactor circuit.

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