Page 244 - Dynamics and Control of Nuclear Reactors

APPENDIX B Advanced reactors 245

creating a neutron spectrum with few neutrons at energies where the Pa-233 cross
section is large. This is essential in order to achieve breeding (producing as much
or more fissile material that is being consumed).
Reactors that produce Pu-239 from U-238 also have intermediate isotopes that
can absorb neutrons. The reactions are as follows:
U-238 + n ! U-239 ! Np-239 + β ! Pu-239 + β (B.2)
The Np-239 is the isotope of concern. But it has a fairly short half-life (at least as
compared to Pa-233 in the Th-232/U-233 case) and a small appetite for neutrons
compared to fissile isotopes. Therefore, there is no incentive to separate and seques-
ter Np-239 in U-238/Pu-239 reactors. It is also noted that separation and sequestra-
tion of Pa-233 yields pure U-233 that represents a proliferation risk.

B.4 Advanced reactor marketplace

The marketplace for advanced reactors is one of intense competition and change.
Companies have merged, international cooperative partnerships have been forged
and some countries that previously imported reactors have developed domestic capa-
bility and even export capability. The story of these developments is long, complex
and beyond the scope and purpose of this book.
The following list shows the 2018 status of advanced rector activity, including
reactors in operation, reactors under construction and reactors in development
(see Refs. [1, 2] unless otherwise noted for detailed information.):

• Pressurized Water Reactors: at least 12 (note predominance).
• Boiling Water Reactors: at least 3
• Pressurized Heavy Water Reactors: at least 2
• Liquid Metal Fast Reactors: at least 4
• High Temperature Gas-Cooled Reactors: at least 1 (see Ref. [3, 4]. Also much
work on small HTGRs)
• Molten Salt Reactors: at least 2 (See Ref [5]. Also much work on integral MSRs)
• Advanced Heavy Water Reactor: at least 1.

The information presented above is only a snapshot of the situation in 2018. The list
will surely change in the future. Interested readers can find extensive up-to-date
information about nuclear plant suppliers and their designs in the literature (includ-
ing information on the internet). The World Nuclear Association is an excellent
source of information.
The way that the development evolves will determine which reactors are built,
where reactors are built, who will build them and who operates them. All of these
developments will create a growing need for engineers with capabilities in dynamic
analysis and control system design.