42 / 386
BUSINESS OVERVIEW
06
The world’s most prevalent reactor: the pressurized
water reactor
In light water reactors, the fuel is low-enriched uranium. The water in the
primary cooling systembathes the reactor core, consisting of tubes containing
the fuel, which heats up as a result of the fission reactions.
In pressurized water reactors (PWR), the water is heated by the tubes
containing the fuel and transfers its heat via heat exchangers to a secondary
cooling system, where the water is converted into steam. The nuclear steam
supply system consists of the reactor core and the steamgenerators, together
with the pressurizer, the reactor coolant pumps, and the hot and cold legs
connecting the pumps. The primary cooling system is separate from the
secondary cooling system, which produces steam to drive the turbo-generator,
making radioactive containment that much stronger.
PWR reactors have a triple barrier system to prevent the release of radioactive
fission products. The primary barrier in this system consists of the metal tubes
containing the fuel. The secondary barrier consists of the separate primary
and secondary cooling systems. The third barrier is comprised of the nuclear
steam supply system enclosed in a concrete containment building capable
of containing hazardous products in the event of a leak. All of the reactors in
the French nuclear reactor fleet are PWRs, which represent the majority of
reactors in service around the world.
PRESSURIZED WATER REACTOR
Primary cooling system
Secondary cooling system
steam
water
Reactor
coolant
pump
Control
rod drive
mechanisms
Pressurizer
Steam generator
Reactor
core
Reactor
vessel
Reheater
Feedwater
pump
Cooling water
Condenser
Generator
Source:AREVA.
Boiling water reactors (BWR) are generally comparable to PWRs. The main
differences are that the water boils when it comes into contact with the fuel,
and there is only one steam system. The fuel core releases its heat to the water
passing through it, which vaporizes at the top of the vessel containing the core.
The resulting steam drives the turbine, then cools when it comes into contact
with the cold source and is liquefied in the condenser before it is recirculated
to the reactor vessel. Thus, in a BWR, the water is in a closed cycle in which
the steam produced in the reactor core expands directly into the turbine.
BOILING WATER REACTOR
Reactor
core
Reactor water
recirculation
pumps
Control rod drive
mechanisms
Heater
Cooling
water
Feedwater
pump
Feed water
Generator
Primary cooling system
Steam-water system
Reactor
vessel
Steam
Condenser
Source:AREVA.
AREVA is active in both of these reactor systems.
Difference between generation II and generation III
reactor systems
Nuclear reactor technologies are classified in terms of generation. The timeline
for the different generations corresponds to the date at which the related
technologies become mature. Most of the reactors currently in service around
the world are generation II reactors consisting mainly of PWRs and some
BWRs. AREVA’s generation III reactor models are based on evolutionary
technology with additional features which factor in operating experience
from previous generations of reactors, particularly in terms of nuclear and
industrial safety.
Renewable energies
Renewable energies – hydropower, biomass, wind, solar, geothermal and
ocean energies – do not consume natural resources for their operations.
Their efficiency is contingent on their location (dam site, wind, sunshine, etc.).
Some of these energy sources are spread out and intermittent, which makes
them less suitable for centralized baseload power generation. Others aremore
flexible and allow relatively high power densities to be achieved.
Since the group is refocusing on operations related to the nuclear fuel cycle,
AREVA has decided to gradually withdraw from the renewable energies
segment. AREVA’s operations in renewable energies are presented in
Section 6.4.3.2.
Renewable Energies operations.
42
2016 AREVA
REFERENCE DOCUMENT