Design of a Functionally Graded Composite for Service in High Temperature Lead and Lead-Bismuth Cooled Nuclear Reactors
Author(s)
Short, Michael P.; Ballinger, Ronald G.
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Advanced Nuclear Power Technology Program (Massachusetts Institute of Technology)
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A material that resists lead-bismuth eutectic (LBE) attack and retains its strength at 700°C
would be an enabling technology for LBE-cooled reactors. No single alloy currently exists
that can economically meet the required performance criteria of high strength and corrosion
resistance. A Functionally Graded Composite (FGC) was created with layers engineered to
perform these functions. F91 was chosen as the structural layer of the composite for its
strength and radiation resistance. Fe-12Cr- 2Si, an alloy developed from previous work in
the Fe-Cr-Si system, was chosen as the corrosion-resistant cladding layer because of its
chemical similarity to F91 and its superior corrosion resistance in both oxidizing and
reducing environments.
Fe-12Cr-2Si experienced minimal corrosion due to its self-passivation in oxidizing and
reducing environments. Extrapolated corrosion rates are below one micron per year at
700°C. Corrosion of F91 was faster, but predictable and manageable. Diffusion studies
showed that 17 microns of the cladding layer will be diffusionally diluted during the three
year life of fuel cladding. 33 microns must be accounted for during the sixty year life of
coolant piping.
5 cm coolant piping and 6.35 mm fuel cladding were produced on a commercial scale by
weld-overlaying Fe-12Cr-2Si onto F91 billets and co-extruding them, followed by pilgering.
An ASME certified weld was performed followed by the prescribed quench-and-tempering
heat treatment for F91. A minimal heat affected zone was observed, demonstrating field
weldability. Finally, corrosion tests were performed on the fabricated FGC at 700°C after
completely breaching the cladding in a small area to induce galvanic corrosion at the
interface. None was observed.
This FGC has significant impacts on LBE reactor design. The increases in outlet
temperature and coolant velocity allow a large increase in power density, leading to either a
smaller core for the same power rating or more power output for the same size core. This
FGC represents an enabling technology for LBE cooled fast reactors.
Date issued
2010-10Publisher
Massachusetts Institute of Technology. Center for Advanced Nuclear Energy Systems. Advanced Nuclear Power Program
Series/Report no.
MIT-ANP;TR-131