Thermal analysis of supercritical CO2 power cycles: assessment of their suitability to the forthcoming sodium fast reactors

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Sodium fast reactors (SFRs) potential to meet Gen. IV requirements is broadly acknowledged worldwide.
The scientific and technological experience accumulated by operating test reactors and, even, by running
commercial reactors, makes them be considered as the closest Gen. IV option in the near future. In the
past their balance of plant has been always based on Rankine cycles.
This paper investigates the potential use of supercritical recompression CO2 cycles (S-CO2) in SFRs on
the basis of the working parameters foreseen within the European Sodium Fast Reactor (ESFR) project. A
wide range of configurations have been explored, from the simplest one to combined cycles (with organic
Rankine cycles, ORC), and a comparison has been set in terms of thermal efficiency. As a result, it has been
found out that the most basic configuration could reach a thermal efficiency as high as 43.31%, which
is comparable to that obtained through super-critical Rankine cycles proposed elsewhere. A sensitivity
analysis together with an exergy study of this configuration, pointed the pre-cooler and IHXNa CO2 as key
components in the cycle performance. These results highlight a main conclusion: the potential use in
SFRs of recompression S-CO2 cycles for their balance of plant, whenever a sound and extensive database
is built-up on S-CO2 turbo-machinery and IHX performance.