PhD Defense | Aleksandr Tsybanev | Chemistry of Corrosion Products in Lead-bismuth Cooled Nuclear Systems: Oxides and Intermetallics of Iron, Nickel and Manganese

Chemistry of Corrosion Products in Lead-bismuth Cooled Nuclear Systems: Oxides and Intermetallics of Iron, Nickel and Manganese

Introduction / Objective
MYRRHA (Multi purpose hYbrid Research Reactor for High tech Applications) is a unique facility combining a linear particle accelerator and a subcritical nuclear reactor. One of the key components of MYRRHA is its coolant, a liquid metal called lead bismuth eutectic (LBE), whose purity must be strictly controlled. During operation, the stainless steels of the reactor continuously release corrosion products. This research is dedicated to addressing the behavior of these corrosion products, which is necessary to design an oxygen control strategy for MYRRHA.

Research Methodology
The methodology of this work relies heavily on the use of potentiometric oxygen sensors, which provide a highly accurate in situ method to measure the dissolved oxygen concentration (DOC) in LBE. Combined with thermodynamics, this technology allows studying oxides in LBE, their equilibrium and kinetics. Furthermore, the DOC measured at the oxide equilibrium can be used to characterize the behavior of metallic impurities, particularly their activity coefficient in LBE to model their interaction with each other and LBE. 

Results & Conclusions

• This research has identified the formation of iron(III) oxide (Fe₂O₃), nickel oxide (NiO) and manganese(II)oxide (MnO) in LBE.
• Fe₂O₃ forms on the surface of precipitates of iron(II,III) oxide (Fe 3 O 4 ) suspended in LBE. Surprisingly, and at first counterintuitive, this reaction slows down at higher temperatures.
• The activity coefficient of Ni in LBE and the activity coefficient of Mn in LBE have been measured.
  For Ni, these data bring to an agreement different literature data on the formation of Bi₃Ni a dangerous solid precipitate that could block narrow channels in the reactor.
  For Mn, these data allowed to calculate the conditions for the βBiMn formation in LBE.

Promoter:

• Nele Moelans (KU LEUVEN)

SCK CEN mentors:

• Alessandro Marino