In general, a nuclear reactor is a device used to initiate and control a self-sustained nuclear chain reaction. Since nuclear reactors are used in nuclear power plants, research facilities, or nuclear-propelled ships, their output is thermal energy, or they can be used as a source of neutron radiation.
Main Components of Nuclear Reactor
The key components common to most PWR-type nuclear reactors are:
Nuclear reactor core. The reactor core is a bounded region where neutron multiplication occurs and where a chain reaction takes place. The reactor core contains especially the nuclear fuel (fuel assemblies), the moderator, and the control rods.
- Reactor pressure vessel. The reactor pressure vessel is the pressure vessel containing the reactor core and other key reactor internals. It is a cylindrical vessel with a hemispherical bottom head and a flanged and gasketed upper head. The bottom head is welded to the cylindrical shell, while the top head is bolted to the cylindrical shell via the flanges. The top head is removable to allow for the refueling of the reactor during planned outages.
- Neutron reflector. The reactor core is surrounded by a neutron reflector or reactor core baffle. The reflector reduces the non-uniformity of the power distribution in the peripheral fuel assemblies, reduces neutron leakage, and reduces a coolant flow bypass of the core.
- Lower support structure.
- Surveillance capsule assembly. The capsules contain reactor vessel steel specimens obtained during vessel fabrication and are withdrawn periodically from the reactor vessel.
- Core support barrel. The core barrel belongs to the lower core support structure because it houses a reactor core.
- Upper guide structure assembly.