What is a PWR nuclear power plant? How a nuclear pressurized water reactor works

Boiling water reactor is literally a reactor that uses boiling water to cool nuclear fuel, and its working principle is: cooling water flows into the core from the bottom of the reactor, cools the fuel rods, takes away the heat energy generated by fission, the cooling water temperature rises and gradually vaporizes, and finally forms a mixture of steam and water, which passes through a steam water separator and a steam dryer, and uses the separated steam to drive the steam turbine to generate electricity. The Fukushima nuclear power plant was built in the 70s of the 20th century and is a boiling water reactor.

The PWR is literally a kind of reactor that uses high-pressure water to cool nuclear fuel, and its working principle is as follows: the main pump sends 120 160 atmospheres of primary circuit cooling water into the core, brings the heat energy released by the nuclear fuel out of the core, and then enters the steam generator, and transfers the heat to the secondary circuit water through the heat transfer tube, so that it boils and produces steam; The temperature of the primary circuit cooling water drops, enters the reactor core, and completes the primary circuit water circulation; The high-pressure steam generated by the secondary circuit pushes the steam turbine to generate electricity, and then enters the steam generator through the condenser and preheater to complete the secondary circuit water circulation. A total of 13 nuclear power units have been built or are under construction in China, all of which are pressurized water reactors, with the exception of Qinshan Phase III, which uses CANDU reactor technology, and Shandong Rongcheng, which uses high-temperature gas-cooled reactors.

There are currently about 440 nuclear power units in operation worldwide, of which the vast majority (about 92%) are light water reactors (LWRs) and the rest are heavy water reactors and advanced gas-cooled reactors. Light water reactors are mainly pressurized water reactors (and boiling water reactors, of which about 75% are pressurized water reactors, and the vast majority of nuclear power plants put into operation and built in China are pressurized water reactors. Since the advent of nuclear power plants, there are three main types of industrially mature power generation reactors:

And. They were used in three different nuclear power plants accordingly, forming the modern mainstay. Currently, most of them are so-called LWRs that are moderated and cooled with light water.

LWRs are further divided into and. Pressurized water reactor nuclear power plants use light water as a coolant and moderator. It is mainly composed of nuclear steam ** system (i.e., primary circuit system), steam turbine generator system (i.e., secondary circuit system) and other auxiliary systems.

After the coolant absorbs the heat energy released by the fission of nuclear fuel in the core, it transfers the heat to the secondary circuit through the steam generator to generate steam, and then enters the steam turbine to do work to drive the generator to generate electricity. The system of a PWR nuclear power plant is completely separated from it, it is a closed circulation system. The principle flow of the nuclear power plant is as follows:

The main pump feeds high-pressure coolant into the reactor, which is generally maintained at 120 160 atmospheres. At high pressures, the temperature of the coolant is not even more than 300 °C. The coolant takes the heat energy released by the nuclear fuel out of the reactor and into the steam generator, where it passes through thousands of heat transfer tubes to the secondary circuit water outside the tubes, causing the water to boil to produce steam; After the coolant flows through the steam generator, it is fed into the reactor by the main pump, and so on and so on, continuously bringing out the heat in the reactor and converting it to produce steam.

The high-temperature and high-pressure steam coming out of the steam generator drives the steam turbine to generate electricity. The exhaust steam condensed into water, which was then fed to the heater by condensation, reheated and sent back to the steam generator. This is the two-loop circulation system.

The condenser is made of river water pumped by the three-circuit circulation pump, which is discharged back into the river after cooling to form the third circuit circulation. <>

Ordinary pressurized water reactors: ordinary water (called light water, to distinguish it from heavy water) as a coolant and moderator

The role of the coolant is to transfer the heat released by nuclear fission to produce steam to drive the steam turbine. The role of the moderator is to slow down the neutrons produced by nuclear fission to increase the number of neutrons in the reactor.

reduce the escape rate.

The difference between a PWR and a boiling water reactor is that in a boiling water reactor, the light water as a coolant directly turns into steam and enters the steam turbine to do work, while in a PWR, the light water as a coolant remains in a liquid state at a general temperature.

320-350 degrees Celsius.

The pressure is 15-18MPa.

After such high-temperature water leaves the reactor, it is exchanged with the feed water in a steam generator, and the feed water is heated into steam, which is sent to the steam turbine for work, and the coolant light water after cooling is returned to the reactor. The advantage of a PWR over a boiling water reactor is that the steam entering the steam turbine is not radioactive.

It is possible not to steam turbines, condensers.

Make a special design.

There is also a pressurized tubular reactor that uses heavy water as a moderator (because it absorbs almost no neutrons) and light water as a coolant. The coolant is in a tube with high temperature and high pressure, while heavy water is not maintained at high temperature and high pressure, and is generally at ordinary atmospheric pressure.

state, 70 degrees Celsius. This is done to reduce the loss of heavy water. Because heavy water is expensive.

Pressurized water reactor is the most widely used reactor type for nuclear submarines, and the principle is: the uranium-235 nuclear fuel in the nuclear reactor is used for a chain nuclear reaction and produces high temperature, and the high temperature "boils" the pure water in the nuclear reactor into steam, and then accelerates it into a steam flow through the nozzle to promote the operation of the steam turbine. The speed of the steam turbine is decelerated by the reduction gear to drive the propeller.

The whole process of energy conversion is roughly as follows: nuclear energy, thermal energy, mechanical energy, and kinetic energy.

Nuclear energy is produced by the fission of uranium nuclei in nuclear reactors, and when uranium nuclei are continuously fissioned (called "chain reaction"), a huge amount of heat energy is produced. The function of a nuclear reactor is similar to the boiler that we are all familiar with, but the water in the boiler is generally heated by fire, while the water in the nuclear reactor is "heated" by nuclear fuel, so in the past, the nuclear reactor was also commonly referred to as an "atomic boiler".

A nuclear power plant usually consists of a primary circuit and a secondary circuit, both of which are closed recirculating circuits.

The primary circuit is composed of the main coolant system and various auxiliary systems, and the main coolant system includes nuclear reactors, main coolant pumps, steam generators, voltage regulators and other equipment. After the high-temperature and high-pressure purified water in the primary circuit is heated by the nuclear fuel, it is pushed by the main coolant pump, and the heat is conducted to the secondary circuit water through the steam generator to turn it into steam, and then the cooled water in the primary circuit returns to the nuclear reactor again, continuing to bring out the heat generated by the nuclear fuel, and moderating the neutrons to participate in the chain nuclear reaction. So the water in the primary circuit is called a coolant and a moderator.

The amount of heat released by nuclear fuel is regulated by the control rods.

In the secondary circuit, the first half of the flow is the steam heated by the primary circuit, and the second half of the flow is the water that has been cooled by the condenser. At the intersection of the primary and secondary circuits is the steam generator, and the water in the secondary circuit is heated in the steam generator and turned into saturated steam to drive the steam turbine generator and provide power supply.

Yangjiang is located in the southwest coast of Guangdong Province, China.

A nuclear power base frequented by white dolphins

Coming to the viewing platform, you can see the panoramic view of Yangjiang nuclear power. Yangjiang Nuclear Power Plant is surrounded by mountains on three sides, one side is facing the sea, and surrounded by greenery, Yangjiang Nuclear Power Unit 1 and No. 6 are lined up in turn, forming a quiet and peaceful scene with the rippling sea surface in the distance under the reflection of the setting sun. On top of the mountains, a patchwork of iron towers sends the green electricity generated by Yangjiang Nuclear Power Plant to distant places.

It is these six units that have established Yangjiang Nuclear Power's position as the world's largest operating light-water pressurized water reactor nuclear power base.

Not only clean power, Yangjiang nuclear power has made important contributions to the development of China's nuclear power industry in many aspects, and the first set of domestic independent nuclear-grade DCS (digital instrumentation and control system for nuclear power plants) is the best example of the application in Yangjiang nuclear power base.

The localization rate of equipment has increased from 75% to 85%.

The realization of the "harmony system" in the million-kilowatt nuclear power project of the first set of application is only a microcosm of Yangjiang nuclear power in the development process of independent innovation, in the discussion reporter also learned that looking at the construction process of Yangjiang nuclear power is to look at the history of technological innovation of CGN.

1. The core fission heats, and the heat is carried away by 15 Pascals flowing from the core and 300 degrees Celsius of high-pressure water;

2. When the high-pressure water flows through the steam generator, the heat is transferred to the secondary circuit water on the other side of the pipe, which enters the main pump after cooling, and then is beaten back to the core by the main pump;

3. The secondary circuit water in the steam generator is changed from high-pressure water of several Pascal to high-pressure and high-temperature steam, and the steam works through the steam turbine to drive the generator to generate electricity;

4. After the work is done, the steam is cooled to 40 degrees Celsius in the condenser, and then passes through the deaerator and becomes high-pressure water after the water pump and returns to the steamer and shouting friend.

1. The core fission heats, and the heat is carried away by 15 Pascals flowing from the core and 300 degrees Celsius of high-pressure water;

2. When the high-pressure water flows through the steam generator, the heat is transferred to the secondary circuit water on the other side of the pipe, which enters the main pump after cooling, and then is beaten back to the core by the main pump;

3. The secondary circuit water is changed from high-pressure water in several Pascal to high-pressure and high-temperature steam in the steam generator, and the steam passes through the steam turbine to do work to drive the generator to generate electricity;

4. After the work is done, the balanced steam is cooled to 40 degrees Celsius atmospheric water by seawater in the condenser, and then passes through the deaerator and becomes high-pressure water after the water pump and returns to the evaporator.

The first 300,000 kW pressurized water reactor nuclear power plant was built at the Qinshan Nuclear Power Plant in Haiyan County, Jiaxing City, Zhejiang Province.

Qinshan Nuclear Power Plant adopts the world's most mature pressurized water reactor, and the nuclear island adopts three barriers: fuel cladding, pressure shell and containment, which can withstand internal pressure, high temperature and various natural disasters caused by extreme accidents. It is 100% controlled by China National Nuclear Corporation, and China Nuclear Power Operation Management is responsible for operation management. It is the nuclear power base with the largest number of nuclear power units, the most abundant reactor types and the largest installed capacity in China before Muyanhuai.

A nuclear power plant is a facility that converts nuclear energy into electricity through appropriate installations. Nuclear power plants use nuclear reactors instead of boilers in thermal power stations, and nuclear fuel is used to produce heat through a special form of "combustion" in the nuclear reactor, so that nuclear energy is converted into heat energy to heat water and produce steam. The systems and equipment of a nuclear power plant usually consist of two main parts:

nuclear systems and equipment, also known as nuclear islands; Conventional systems and equipment, also known as conventional islands.

The four major components in the nuclear island of a PWR nuclear power plant are the reactor pressure vessel, the main steam piping system, the steam generator, and the reactor core. These four components are the core part of the nuclear island, and they are also the core systems to ensure the operation of the nuclear power plant. Among them, the reactor pressure vessel is the storage vessel for the core fuel of the nuclear reactor and the main part of the nuclear reaction.

It needs to withstand the high temperatures, pressures, and radiation of nuclear reactions, so it requires a very high level of technology and quality in both design and manufacturing.

The main steam piping system connects the reactor to the steam turbine units. It transports high-temperature and high-pressure steam to the steam turbine to drive power generation, and can also guide the steam back to the reaction and distribution reactor for secondary use. The quality and reliability of the main steam piping system is one of the guarantees for the normal operation of nuclear power plants.

The steam generator is a key component in the thermal system of a nuclear power plant, connecting the reactor to the steam turbine. In a nuclear reactor, the coolant is heated in a pressure vessel and then flows into a steam generator. In the steam generator, the coolant exchanges heat with the water vapor in the water insulation shell, so that the water vapor flows into the steam turbine at high temperature and high pressure to generate power to drive power generation.

The reactor core is a key part of the nuclear reactor, it is the generator of the nuclear reaction. The reactor core contains reactor fuel, which continuously releases and releases energy through a nuclear chain reaction, which in turn generates heat and distributes electricity. However, the control and maintenance of the reactor core is also the most difficult part, requiring rigorous testing and maintenance work to ensure that the nuclear reaction is carried out properly.

In short, the four major components of the reactor pressure vessel, the main steam piping system, the steam generator and the reactor core are the most important components of the nuclear island, which are related to the stable operation and safe power generation of the nuclear power plant. Through continuous technological innovation and improvement, we believe that nuclear power technology will bring more clean and safe energy to mankind in the future.