Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.
Currently there are a number of Generation IV
SuperCritical Water-cooled nuclear Reactor (SCWR)
concepts under development worldwide. The main objectives
for developing and utilizing SCWRs are: 1) Increase gross
thermal efficiency of current Nuclear Power Plants (NPPs)
from 33 – 35% to approximately 45 – 50%, and 2) Decrease
the capital and operational costs and, in doing so, decrease
electrical-energy costs (~$1000 US/kW or even less).
SCW NPPs will have much higher operating parameters
compared to current NPPs (i.e., pressures of about 25 MPa
and outlet temperatures up to 625°C). Additionally, SCWRs
will have a simplified flow circuit in which steam generators,
steam dryers, steam separators, etc. will be eliminated.
Furthermore, SCWRs operating at higher temperatures can
facilitate an economical co-generation of hydrogen through
thermo-chemical cycles (particularly, the copper-chlorine
cycle) or direct high-temperature electrolysis.
To decrease significantly the development costs of a
SCW NPP, to increase its reliability, and to achieve similar
high thermal efficiencies as the advanced fossil steam cycles
it should be determined whether SCW NPPs can be designed
with a steam-cycle arrangement that closely matches that of
mature SuperCritical (SC) fossil power plants (including their
SC turbine technology). The state-of-the-art SC steam cycles
in fossil power plants are designed with a single-steam reheat
and regenerative feedwater heating and reach thermal steamcycle
efficiencies up to 54% (i.e., net plant efficiencies of up
to 43% on a Higher Heating Value (HHV) Basis).
Therefore, simplified no-reheat, single-reheat, and
double-reheat cycles without heat regeneration and a singlereheat
cycle with heat regeneration based on the expected
steam parameters of future SCW NPPs were analyzed in
terms of their thermal efficiencies.
On this basis, several conceptual steam-cycle
arrangements of pressure-tube SCWRs, their corresponding
T–s diagrams and steam-cycle thermal efficiencies (based on
constant isentropic turbine and polytropic pump efficiencies)
are presented in this paper.