Page 15 - Dynamics and Control of Nuclear Reactors

6 CHAPTER 2 Nuclear reactor designs

The first successful application of a nuclear reactor for energy production was
military, the propulsion plant for the USS Nautilus, a submarine commissioned in
1955. The Nautilus used a pressurized water reactor supplied by Westinghouse
for the U.S. Navy. The success of the Nautilus led to the construction and operation
of the first U.S. land-based power reactor, the Shippingport 60MWe reactor in Penn-
sylvania, commissioned in 1957. The Shippingport reactor was the prototype of the
large pressurized water reactors that were built subsequently in the U.S. and other
countries. Another power reactor that was to be the prototype of large-scale commer-
cial reactor systems was the 200MWe Dresden boiling water reactor, commissioned
in Illinois in 1960.
While the U.S. focused on development of large pressurized water reactors
(PWRs) and boiling water reactors (BWRs), Canada focused on power reactors using
heavy water. These plants are called CANDU (acronym for CANada Deuterium Ura-
nium) reactors.
The development of gas-cooled reactors in the United Kingdom started with the
Calder Hall Magnox reactor, commissioned as a Generation I reactor in 1956. The
Magnox reactor used natural Uranium as the fuel with graphite as the moderator and
carbon dioxide gas as the coolant. The term magnox comes from the magnesium-
aluminum cladding used to fabricate the fuel elements.
Reactors built in the early years (1950s through early 1960s) are usually referred
to as Generation I reactors.

2.3 Generation II reactors
Generation II reactors are the large commercial reactors (typified by PWRs and
BWRs) built in the U.S. and elsewhere in the 1960s up to the end of the 1990s. Since
analysts often need to acquire plant parameters, Appendix A provides typical design
data for Generation II PWRs, BWRs and CANDU reactors.
In addition to PWRs, BWRs and CANDU reactors, Generation II reactors
include, Advanced Gas-cooled Reactors (AGRs) in the UK, Russian Vodo-Vodyanoi
Energetichesky Reactors (VVERs), and the Russian RBMK reactors.
In a PWR, water flows over fuel rods in the reactor core and extracts heat. The
heated water passes through piping and into tubes inside the steam generators. A sec-
ond stream of water flows outside of the tubes of the steam generators (on the shell
side) where boiling occurs. There are two main types of steam generators in U.S.
designs: the U-tube recirculation type and the once-through type. The Russian
VVERs use horizontal steam generators. Figs. 2.1, 2.2, and 2.3 show the main com-
ponents of the two types of U.S. PWRs. Details pertinent to PWR dynamics and
control are presented in Chapter 12.
In a BWR water flows over fuel rods, extracts heat and boils. After separating the
steam from liquid water, the saturated 100% quality steam passes to the turbine.
Fig. 2.4 shows a schematic of a BWR. Details pertinent to BWR dynamics and con-
trol appear in Chapter 13.