Page 242 - Dynamics and Control of Nuclear Reactors

APPENDIX

B
Advanced reactors

B.1 Introduction
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Advanced reactor designs (labeled Generation III, III and IV reactors) have been
prepared and a few advanced reactors are operating at the time when this book
was prepared (2019). Features of advanced reactors were summarized in Ref. [1]
and are quoted below:
“A more standardized design for each type to expedite licensing, reduce capital
cost and reduce construction time.
A simpler and more rugged design, making them easier to operate and less
vulnerable to operational upsets.
Higher availability and longer operating life—typically 60years.
Further reduced possibility of core melt accidents.
Substantial grace period, so that following shutdown the plant requires no
active intervention for (typically) 72h.
Stronger reinforcement against aircraft impact than earlier designs, to resist
radiological release.
Higher burn-up to use fuel more fully and efficiently, and reduce the amount of
waste.
Greater use of burnable absorbers (‘poisons’) to extend fuel life.”
Advanced reactor designs include the use of passive safety systems. These systems
operate if an accident occurs without actuation by an operator, without actuation in
response to measured signal by an engineered system and without a need for elec-
trical power. Passive systems depend on natural processes such as gravity, natural
circulation, relief valve operation and melting of freeze valves.
Advanced reactors achieve lower cost and faster construction by use of shop fab-
ricated components rather than on-site fabrication of those components. This is
called modular design. Many of the reactors employ “integral” designs. That is, they
position other components, such as steam generators and pressurizers, as well as the
reactor core inside the same vessel. This enhances safety but increases the required
size of the vessel.

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