Many people in the beginning of the conversation about the nuclear power plants immediately begin to say that it is very dangerous and they should be rejected. They are partly right, but their fears are greatly exaggerated. In order to get rid of this stereotype, you just have to understand how the station operates and to ensure that the release of radioactive elements into the environment is simply impossible. Of course, if the station is functioning normally. The only question is, how it works and where the boundaries of this regular regime. Today let’s talk about the design of nuclear power plants, their types and how they produce electricity through the fission of uranium atoms. To tell you’ll in simple language.
When the first nuclear power plant
The first major step towards the use of the properties of the fission of the atom, including nuclear weapons and peaceful nuclear energy, has become the test of the first atomic bomb in 1945. It happened on July 16 at the test site in new Mexico. During those tests, many have realized that the horrors of the Second world war, a little faded on the background that could occur if such a weapon earlier.
In the USSR, the first nuclear test at the site took place only 4 years later — on 29 August 1949. Since then the two major powers was a technology that allowed not only to intimidate each other with his power, but to work for the benefit of peaceful nuclear energy and the application of this destructive power in order to bring light and warmth to every home.
The first nuclear power plant was launched in 1954 in the town of Obninsk in Moscow region. The inspirer and leader of the project was the famous Soviet physicist, academician of the USSR and part-time “father” of the Soviet atomic bomb Igor Kurchatov.
How much energy is produced by nuclear power plants
Of course, the first nuclear power plant is difficult to compare with modern, but it marked the beginning of a new way of producing energy, as the first iPhone started the process of smartphone and T Ford mass production of cars.
Since then, the number of nuclear power stations in the world has increased dramatically and reached 192 pieces (total 438 units) in 31 countries. 10 nuclear power plants located in Russia (total 33 units). According to this indicator our country ranks eighth in the world and energy production — the fourth.
The total energy output is about 392 MW. Among the leaders are the USA (103 MW), France (66 MW), Japan (46 MW), Russia (25 MW) and South Korea (21 MW). It is quite a lot and statistics show that nuclear plants provide 16 percent of electricity consumed in the world.
High interest in nuclear power plants and their widespread use due to the fact that their efficiency is 40-45%, and over, and the risks are substantially less, even with all the terrible accident that occurred. On the one hand, it seems that if it explodes, you will not find it, but on the other hand, fatalities per 1 kilowatt is obtained, the statistics show that NPP 43 times less than that of thermal power plants.
Dangerous nuclear power station
The result is a situation in which nuclear energy is similar to the situation with the aircraft. Many people are afraid of them, but in reality, the risk of dying on the street hundreds of times higher than crashing in a plane. Just crash evoke a great response and one-time kills more people, but such accidents are rare.
In addition to systems, most nuclear power plants, which we will discuss below, they are accompanied by serious precautionary measures. Frankly, when I was near Voronezh NPP I was a little nervous, but when I gathered more information, I realized that I overstated the case.
Around any nuclear power station has at least a 30-kilometer area, which is continually monitoring the situation and the environmental situation. It’s not a exclusion zone, as it is possible for people to live and even to engage in agriculture. The only limits are the three-kilometer zone in the vicinity of the station. But again, this is done only for the purpose of additional security, and not due to the fact that it is dangerous to be in.
Probably the most dangerous period of station operation is the time of fuel loading. It was at this point the reactor is opened and there is little risk of radioactive waste into the air. However, this is not done often (on average once a year) and the release will be very small.
What works nuclear power plant
The main element of running a nuclear plant is uranium-235, which is loaded into the reactor in special cartridges, which are called fuel elements (TVEL). In a single reactor may contain several tens and even hundreds.
The fuel delivered to the reactor on special platforms, and download them to his cock. The same crane participated in the construction of the station and was loaded in a special capsule in the reactor itself
The average reactor uses about ten pounds of fuel. It is such a small volume highlights the amount of energy, which produces station. If we talk about the performance of nuclear fuel, we can say that one gram of uranium-235 allows you to get as much energy as the burning of fuel produced from two tons of oil. In the end, only ten kilos of fuel is equivalent to approximately seven hundred oil tanks.
What are nuclear plant
Many people think that radioactive fuel generates electric energy, but it is not so. More precisely, it is not so.
The nuclear power plant can be divided into three main stages. In the first stage, energy from the fission of the atom is transferred into heat energy. In the next step the thermal energy transferred to the mechanical. After that, the conversion of mechanical energy into electricity becomes a matter of technique.
The reactors are divided into three main types: single-circuit, double-circuit, three-circuit. In the beginning we will understand how works the dual-circuit scheme, and later on her example, let’s see how the rest of the types.
How does a nuclear power plant
The initial stage of energy release is, as I said above, the reactor. It is placed in a special closed loop, which is called first. It is, in fact, a big pan, but rather a pressure cooker as the liquid inside it are under great pressure. So to increase the boiling point and raise the temperature of the work of the whole primary circuit.
The capsule, which is a reactor, called germanye and has thick walls (at least 15 cm). This allows it to keep a lot of pressure and does not allow radiation to go out.
The main task of the rector is heat for heating the liquid inside the loop. This happens due to the chain reaction. The basis for such reaction is the fission of atoms by neutrons. However, after fission of a single atom is the new neutrons which continue to divide atoms. Thus the number of neutrons is constantly growing and atoms is divided more and more. It turns out that itself is a chain reaction that maintains itself, but if you do not stop this process, the division will be out of control, energy to stand out too much and the explosion happens. Actually, what happens in a nuclear bomb.
To prevent this from happening inside the rector has special rods with boron, that is very well absorb neutrons and slow down reaction. The rods have a length of several meters, and then continuously enter the reactor, then get out of it, thereby adjusting the division ratio of the neutrons and, as a consequence, the rate of reaction. If this ratio is less than unity, the reaction is inhibited, if it is more accelerated, and if equal to one, then the system supports their work. This unit must be achieved for stable operation of the reactor.
After the reactor heated the water inside the primary circuit to a temperature of about 450 degrees, it passes through the tube and the heat exchanger instantly heats the water in the second circuit. That, in turn, enters the evaporator and is already water vapor with a temperature of about 350-400 degrees spins a huge turbine up to 3000 rpm. This turbine and generates electricity, which goes through the wires in the mains.
Complete isolation of the primary circuit from the second one allows to achieve the protection of the working fluid and wastewater from radioactive contamination. This makes it easy to cool the liquid for further work, because the promotion of the turbine is the latest stage in the second circuit.
After water vapor will spin the blades of a turbine, it falls into a special capacitor, which is essentially a large camera. They steam cools and turns into water.
While the water temperature is still very high and it should be more cooling. To do this, it either directly or through a special channel is supplied to the cooling tower. It’s such a pipe, which can be seen on the territory of thermal power plants. It has a height of about 70 meters, large diameter and tapers towards the top. Normally felled clouds of white steam. Many think it is smoke but it is vapor. Water with a temperature close to the boiling point, is sprayed at the base of the pipe and mixes with the intake air, hovers and cooled. The average cooling tower can cool up to 20,000 cubic meters of water per hour, or about 450,000 cubic meters per day
After cooling, water special pumps fed back into the system for heating and evaporation. Because water requires a lot of nuclear plants are accompanied by large enough bodies of water and sometimes branched system of channels. This allows the station to operate without interruption.
Now you can return to single-loop and three-loop nuclear power plants. The first have a more simple design, since they do not have the second circuit and the turbine spins up directly heated by the reactor water. The difficulty is that water must somehow be cleaned and these stations are less environmentally friendly.
A triple-effect system used at nuclear power plants equipped with reactors on fast neutrons. They are considered to be more promising, but must be supplemented with an additional circuit to avoid contact of radioactive sodium with water. In the additional circuit is predictively sodium.
Of course, the scheme is approximate and simplified. In addition, the station has different technical structure, the command panel, a large number of protective systems which are repeatedly duplicated, and other support systems. In addition, one station has several units, which also complicates the process of its control.
In fact, the current station can operate in automatic mode, but to do it at all without a man. At least, it concerns the process control unit. People need to monitor and make adjustments to the work in the event of an emergency. The risk of occurrence is very low, but just in case for remote duty personnel.
Accidents with radioactive emissions
If we’re talking about accidents at nuclear power plants, let’s discuss how they are classified and which of them were the largest.
To classify accidents according to their severity and the impact on people and nature they are divided into 7 levels on the International nuclear event scale, getting a certain level of INES. Based on this level it is possible to judge whether there were injured people and how the equipment was damaged the station. Not all levels are considered dangerous.
For example, the incidents at Chernobyl (26 April 1986) and at Fukushima-1 (11 Mar 2011) corresponded to the maximum seventh level, and some accidents, which almost no one even found out, corresponded to the fourth level. For example, the explosion at the Siberian chemical combine (Russia), 1993, accident at the nuclear facility Tokaimura (Japan, 1999) and the accident at the Institute for radioelements in Fleurus (Belgium, 2006).
Once I started talking about accidents worth mentioning, and the first accident with radioactive contamination. It occurred at chalk river laboratories Dec 12, 1952.
It happened due to a number of operator errors and failures in the system emergency stop. Reactor in the laboratory was released in supercritical mode of operation. Chain reaction was self-supported and the release of energy is several times higher than normal. In the end, the active zone was damaged and radioactive fission products with long half-life with the mass of cooling water resulted in a basement. For the year, the reactor was fully restored.