Oxygen control systems and impurity purification in LBE: Learning from DEMETRA project

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Operating a system using Lead–Bismuth Eutectic (LBE) requires a control of the dissolved oxygen concentration to avoid corrosion of structural materials and oxide build-up in the coolant. Reliable devices are therefore needed to monitor and adjust the oxygen concentration and to remove impurities during operation. In this article, we describe the learning gained from experiments run in the framework of the DEMETRA project (IP-EUROTRANS 6th FP contract) on the oxygen supply in LBE and on impurity filtration and management in different European facilities. An oxygen control device should supply oxygen in LBE at sufficient rate to compensate loss by surface oxidation, otherwise local dissolution of oxide layers might lead to the loss of steel protection against dissolution. Oxygen can be supplied by gas phase H 2O or O 2, or by solid phase, PbO dissolution. Each of these systems has substantial advantages and drawbacks. Considerations are given on devices for large scale facilities. The management of impurities (lead oxides and corrosion products) is also a crucial issue as their presence in the liquid phase or in the aerosols is likely to impair the facility, instrumentation and mechanical devices. To avoid impurity build-up on the long-term, purification of LBE is required to keep the impurity inventory low by trapping oxide and metallic impurities in specific filter units. On the basis of impurities characterisation and experimental results gained through filtration tests in different loops, this paper gives a description of the state-of-art knowledge of LBE purification with different filter media. It is now understood that the nature and behaviour of impurities formed in LBE will change according to the operating modes as well as the method to propose to remove impurities. This experience can be used to validate the basis filtration process, define the operating procedures and evaluate perspectives for the design of purification units for long-term application in lead-alloys liquid metal coolant systems.