Page 23 - Dynamics and Control of Nuclear Reactors

14 CHAPTER 2 Nuclear reactor designs

Higher temperatures can enable higher thermodynamic efficiencies in electricity
production and can provide process heat for applications such as high-temperature
electrolysis of water to produce hydrogen. The designs under consideration include
both new concepts and resurrection of some older concepts that previously failed to
reach commercialization.
Ref. [4], prepared by OECD Nuclear Energy Agency, provides a technology
roadmap update on generation IV (gen-IV) reactors. The gen-IV reactor concepts
under consideration are the following [4]

• Gas-Cooled Fast Reactor (GCFR): The GCFR is a breeder reactor that uses
helium gas to carry the heat from fuel elements comprising the reactor core.
• Lead-cooled Fast Reactor (LFR): The LFR is a breeder reactor that uses liquid
lead to carry heat from fuel elements comprising the reactor core.
• Molten Salt Reactor (MSR): The MSR is a fluid-fuel reactor. Fuel is dissolved in
a molten salt that flows through the core. The MSR concept permits continuous
processing to remove fission products and add fresh fuel, but this is accomplished
at the cost of complex plumbing and materials handling. MSR designs include
fast reactors (no moderator) and thermal reactors (prismatic graphite block with
channels for fluid fuel-bearing salts)
• Sodium-Cooled Fast Reactor (SFR): The SFR is a breeder reactor that uses liquid
sodium to carry heat from fuel elements comprising the reactor core.
• Supercritical Water-Cooled Reactor (SCWR): The SCWR is an outgrowth of
current designs. It operates at much higher temperatures and pressures than
current light water reactors.
• Very-High Temperature Reactor (VHTR): The VHTR uses helium coolant that
flows through a core consisting of graphite impregnated with fuel particles.
Designs include plants that use the Brayton Cycle instead of a steam cycle. Hot
gas passes directly to a gas turbine in a Brayton cycle.

2.7 Advanced reactors
At the time when this book was written, many new reactor designs were under con-
sideration and a few were experiencing prototype construction. Since the focus of
this book is reactor dynamics and control, most readers would consider inclusion
of detailed descriptions of these designs to be superfluous and unnecessary for their
study. But, since some of these designs will likely be implemented, some readers will
find that they are involved in their analysis and are consequently interested in infor-
mation about them. Information about sodium fast reactors, gas-cooled reactors,
molten salt reactors, and integral small modular reactors is presented in Appendix
B. This appendix is not to be considered as essential material for every reader. Rather
it should be considered as a resource that can be accessed when some of these reactor
designs reach maturity and implementation. It is expected that instructors in univer-
sity courses will choose to alert students that this appendix exists, but probably to
skip it in course presentation.