Nuclear Power Plants: Reactors, Operation, and Safety
Nuclear Power Plants
A thermoelectric central is a source of thermal energy obtained from the fission of uranium and plutonium atoms. The transformations of energy in a nuclear power plant are: nuclear energy (fuel) -> thermal energy (boiler) -> kinetic energy (steam) -> kinetic energy of rotation (turbine) -> power (alternator) -> use.
Nuclear Reactor
The Nuclear Reactor is the most important component of a nuclear power plant and constitutes its core. The reactor is a system that allows you to produce sustained and controlled chain reactions, making it possible to use thermal energy from water to obtain steam that drives the electric generator.
Parts of a Reactor
The reactor vessel is a steel container that contains a pure neutron source and nuclear fuel.
- Moderator: Its function is to reduce the speed of neutrons emitted in fission reactions, to make them impact with other fissionable atoms and keep the reaction going.
- Control Rods: These consist of materials that absorb neutrons, and their mission is to regulate the number of fissions that occur inside the reactor per unit of time.
- Coolant: Its function is to keep the reactor cool, avoid overheating, and transport the heat generated, directly or through a secondary circuit, to the alternator-turbine group, to return to the reactor and then repeat the cycle.
Main Types of Nuclear Plants
- Plants with Pressurized Water Reactors (PWR): These use enriched uranium as fuel and water as both coolant and moderator. The heat produced in the nucleus is transferred through the primary cooling circuit to the secondary circuit to produce steam.
- Boiling Water Reactor (BWR) Plants: These use enriched uranium and water but, unlike the PWR reactor, use only a cooling circuit because the steam is obtained in the reactor, as the water is at a lower pressure and enters boiling. Therefore, the primary circuit is simpler.
- Fast Neutron Reactor Plants: Power reactors with fast neutron reactors use no moderator, so fission occurs with fast neutrons. Because the nuclear reaction is necessary to maintain, the amount of fuel per unit volume is much higher than in thermal reactors.
Components of a Nuclear Facility
- Containment Building: This contains the reactor and the set of elements in the primary circuit, which consists of three loops in parallel. Each one has a pump, pressurizer, and steam generator. This structure, finished with a sphere-shaped dome, is made of thick concrete walls with a special steel lining inside to prevent any emission of radiation outside in case of an accident and is designed to resist the effects of earthquakes.
- Turbine Building: This houses the turbine-alternator group, the reheaters, steam condensers, and preheaters for the water supply.
- Fuel Building: This is used for storing fuel for recharging the reactor and used fuel waiting to be sent for reprocessing.
- Control Building: This houses the control room, which is the nerve center of the plant. Here come the signs and steps of operation of all equipment and safety systems, and the command orders are issued.
- Auxiliary Building: Inside, it provides components and auxiliary security systems, systems and treatments for low-activity radioactive waste, the air conditioning filter equipment, and the containment building.
Operation of a Nuclear Power Plant
The energy generated in the reactor core is extracted and transported by the coolant water, which operates in a closed circuit and at high pressure, and transmitted to the secondary circuit in the steam generators. The steam drives the turbine coupled to the alternator. The electricity produced is delivered to the network after raising the voltage with the transformers. After passing through the turbine, the steam returns to liquid form in the condenser, going back to the steam generator driven by condensation feed pumps. There it will vaporize again, and thus the circuit closes. The water cooling the condenser is in an open circuit. It feeds directly from the river or the sea, is driven by circulation pumps, passes through the condenser, and returns to the river or the sea. If the river flow is low and can cause thermal pollution, the water is cooled prior to passing through forced cooling towers.
Nuclear Safety Systems
- Highly qualified personnel with specialized training appropriate to deal with any emergency.
- Comprehensive annual review of mechanical components of the reactor and primary circuit, making the stop for the recharging of fuel.
- Steady-state control equipment and programmed maintenance.
- Control of all radioactive emissions.
- Detection and identification of any anomaly. If allowable emission limits are exceeded, activation of alarm systems and immediate safety equipment response.
- Radiological environmental monitoring of the area.