On the adoption of carbon dioxide thermodynamic cycles for nuclear power conversion: A case study applied to Mochovce 3 Nuclear Power Plant

- CO2 gas cycles applied to nuclear power stations using real plant data.
- Supercritical, regenerative, recompression reheated SRRR-CO2 cycle used for analysis.
- CO2 net cycle efficiency 34.04% versus 33.51% H2O net cycle efficiency.
- Balance of plant mass 40% reduced with CO2 (as compared with H2O).
- Balance of plant footprint 10 times reduced with CO2 (as compared with H2O).

In this study, closed CO2 cycles are investigated for potential application in existing nuclear power stations, referring in particular to Mochovce power station currently under construction in Slovak Republic. Three different CO2 cycles layouts are explored in the range of temperatures offered by the nuclear source and of the existing cooling towers. The investigation shows that the common opinion that S-CO2 cycles are well suited in the medium to a high temperature range only (higher than about 450 °C) seems unjustified. For a primary heat source with a maximum temperature of 299 °C and a heat sink with a minimum temperature of 19 °C and reasonable assumptions about advanced turbomachines and heat exchanger performances, the supercritical recompressed reheated regenerative CO2 cycle would yield a net efficiency of 34.04%, which compares well with the 33.51% net efficiency of the existing Rankine cycle. The estimated length of the complete turboset (2 turbines, 1 pump and 1 compressor) would be less than 11 m (versus two wet steam turbines of 22 m each for the same power), resulting in a factor of 10 reduction in the footprint of the balance of plant.The total CO2 cycle equipment and main pipelines would have a combined weight of 3957 tons, while in the Mochovce 3 NPP existing Rankine cycle, the main components and connecting piping weigh nearly 7377 tons, thus a 40% reduction.These results suggest that the adoption of CO2 in nuclear power stations would not penalize the plant efficiency and would yield significant savings on installation costs and construction times from the much more compact balance of plant.

Comparison between water and CO2 technologies footprints.91