Assessment of regenerative reheating in direct Brayton power cycles for high-temperature gas-cooled reactors

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Future world energy demand will require a sustainable
energy generation system. Optimization of power
cycles has become a key element to better exploit natural
resources, to minimize waste production, and even to
reduce fuel cycle cost. Aware of this, nuclear technology
is developing what has been termed Generation IV designs.
In particular, the high-temperature gas-cooled reactor
(HTGR) concept is a promising technology to reach
much higher thermal efficiencies than present nuclear
power plants.
By using a classical thermodynamic methodology,
this paper demonstrates that regenerative reheating would
significantly enhance the thermal performance of a reference
Brayton cycle based on pebble bed modular reactor
(PBMR) technology. The regenerative reheating is
conducted by a live gas fraction (b) extracted from the
coolant inventory exiting the nuclear reactor. Optimization
of b results in efficiency values as high as 53 and
61%, respectively, under current and midterm technology
scenarios. In addition, reheating would allow an
effective and easy-to-conduct load-follow operation
with no loss of thermal efficiency in the upper range of
b. Even further, under the midterm technology scenario,
reheating would make it possible to cogenerate H2 from
the enthalpy content of the b fraction exiting reheater.