- at nuclear power plants for electricity generation
- at nuclear research facilities as a neutron source
- as a propulsion of nuclear propelled ships.
- Thermal Reactors. Almost all of the current reactors which have been built to date use thermal neutrons to sustain the chain reaction. These reactors contain neutron moderator that slows neutrons from fission until their kinetic energy is more or less in thermal equilibrium with the atoms (E < 1 eV) in the system.
- Fast Neutron Reactors. Fast reactors contains no neutron moderator and use less-moderating primary coolants, because they use fast neutrons (E > 1 keV), to cause fission in their fuel.
- Pressurized water reactors (PWR) – are characterized by high pressure primary circuit (to keep the water in liquid state)
- Boiling water reactors (BWR) – are characterized by controlled boiling in the primary circuit
Pressurized water reactor – PWR
Pressurized water reactors use a reactor pressure vessel (RPV) to contain the nuclear fuel, moderator, control rods and coolant. They are cooled and moderated by high-pressure liquid water (e.g. 16MPa). At this pressure water boils at approximately 350°C (662°F). Inlet temperature of the water is about 290°C (554°F). The water (coolant) is heated in the reactor core to approximately 325°C (617°F) as the water flows through the core. As it can be seen, the reactor has approximately 25°C subcooled coolant (distance from the saturation).
The hot water that leaves the pressure vessel through hot leg nozzle and is looped through a steam generator, which in turn heats a secondary loop of water to steam that can run turbines and generator. Secondary water in the steam generator boils at pressure approximately 6-7 MPa, what equals to 260°C (500°F) saturated steam. Typical reactor nominal thermal power is about 3400MW, thus corresponds to the net electric output 1100MW. Therefor the typical efficiency of the Rankine cykle is about 33%.
Boiling water reactor – BWR
A boiling water reactor is cooled and moderated by water like a PWR, but at a lower pressure (7MPa), which allows the water to boil inside the pressure vessel producing the steam that runs the turbines. A BWR is like a PWR but with many differents. The BWRs don’t have any steam generator. Unlike a PWR, there is no primary and secondary loop. The thermal efficiency of these reactors can be higher, and they can be simpler, and even potentially more stable and safe. But the disadvantage of this concept is that any fuel leak can make the water radioactive and that radioactivity can reach the turbine and the rest of the loop.
See also: Boiling water reactor
Manufacturing of the Reactor Vessel – Youtube
- Control Element Drive Mechanism
- Reactor vessel head assembly
- Reactor pressure vessel
- Coolant inlet – outlet nozzles
- Downcomer for coolant
- Neutron reflector
- Fuel assemblies
Fuel Consumption – Summary
It is an illustrative example, following data do not correspond to any reactor design.
- Typical reactor may contain about 165 tonnes of fuel (including structural material)
- Typical reactor may contain about 100 tonnes of enriched uranium (i.e. about 113 tonnes of uranium dioxide).
- This fuel is loaded within, for example, 157 fuel assemblies composed of over 45,000 fuel rods.
- A common fuel assembly contain energy for approximately 4 years of operation at full power.
- Therefore about one quarter of the core is yearly removed to spent fuel pool (i.e. about 40 fuel assemblies), while the remainder is rearranged to a location in the core better suited to its remaining level of enrichment (see Power Distribution).
- The removed fuel (spent nuclear fuel) still contains about 96% of reusable material (it must be removed due to decreasing kinf of an assembly).
- Annual natural uranium consumption of this reactor is about 250 tonnes of natural uranium (to produce of about 25 tonnes of enriched uranium).
- Annual enriched uranium consumption of this reactor is about 25 tonnes of enriched uranium.
- Annual fissile material consumption of this reactor is about 1 005 kg.
- Annual matter consumption of this reactor is about 1.051 kg.
- But it corresponds to about 3 200 000 tons of coal burned in coal-fired power plant per year.
See also: Fuel Consumption