What is the principle of nuclear power generation?

Nuclear power plants use energy released by nuclear fission reaction and energy conversion to generate electricity.

The energy of nuclear power generation comes from the fission energy released by the fission reaction of fissile materials (nuclear fuel) in nuclear reactors. Fission reaction refers to the process that heavy elements such as uranium -235, plutonium -239 and uranium -233 are split into two fragments under the action of neutrons, and neutrons and a lot of energy are released at the same time.

In the reaction, the nucleus of fissionable matter absorbs one neutron, then splits and releases two or three neutrons. If these neutrons are consumed, at least one neutron can cause nuclear fission of another atom, so that fission can proceed on its own, then this reaction is called a chain reaction of nuclear fission. Realizing chain reaction is the premise of nuclear power generation.

superiority

There are abundant nuclear resources in the world, such as uranium, thorium, deuterium, lithium and boron. The world's uranium reserves are about 4 1.7 million tons. The available nuclear fuel resources on the earth can provide more than100000 times the energy of fossil fuels. The application of nuclear energy as an economical and effective measure to alleviate the world energy crisis has many advantages:

First, nuclear fuel has many advantages, such as small size and high energy, and nuclear energy is millions of times larger than chemical energy; 1000g uranium releases energy equivalent to 2400t standard coal; 1 10,000 kw large coal-fired power station needs 3-4 million tons of raw coal every year. It takes 2,760 trains to transport these coals, which is equivalent to 8 trains a day, and 40 million tons of ash are also to be transported.

The second is less pollution. Thermal power plants continuously discharge harmful substances such as sulfur dioxide and nitrogen oxides into the atmosphere, and at the same time, a small amount of radioactive substances such as uranium, titanium and radium in coal will also fall around the thermal power plant with smoke and dust, polluting the environment. Nuclear power plants have set up layers of barriers, which basically do not emit substances that pollute the environment, and even radioactive pollution is much less than that of coal-fired power plants.

The third is strong security. Since the first nuclear power plant was built, more than 400 nuclear power plants have been put into operation all over the world, which have been basically safe and normal for more than 30 years. Although the accident 1979 occurred in the pressurized water reactor nuclear power plant in Three Mile Island, USA, and the accident 1986 occurred in the graphite boiling water reactor nuclear power plant in Chernobyl, the Soviet Union, both accidents were caused by human factors. With the further improvement of PWR, nuclear power plants may become safer.

Extended data

Carry out the principle of defense in depth

That is, when designing, it is divided into three levels for security fortification:

First of all, through measures beyond design, quality management and operator training, reliability is improved and accidents are minimized.

Second, establish a safety system to prevent the core from being damaged in case of an accident.

Third, the safety system will try to limit the release of radioactive materials to the environment after the core damage accident with extremely low probability.

Design basis accident (DBA)

Some hypothetical accidents used in the design of safety facilities in nuclear power plants. Different types of nuclear power plants have different DBAs. The DBA of light water reactor includes: water loss accident, rod jumping accident, steam pipe rupture accident, etc. One of the most serious consequences is the water loss accident. In PWR, it is assumed that the double-end fracture of the main pipeline is also called the maximum credible accident.

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