What is the principle of nuclear reactors and why are there so many accidents?
We often say that nuclear reactor refers to fission reactor, which generally uses the huge energy generated by fission of uranium 235 to heat water into high-pressure steam, and finally drives a steam turbine to drive a generator to generate electricity! Why it will cause serious pollution when it leaks, then we must understand its principle!
Is nuclear fission first caused by nuclear fission or by Li Ze? Otto Metenas? Hahn, Fritz? Strassman and Otto? Robert? Scientists such as Frish discovered it in 1938. Its principle is actually quite simple. Heavy nuclei split into lighter nuclei, and slight mass loss will occur in the process. These lost masses can be expressed by the mass-energy equation E=MC? Calculated, because the speed of light is a very huge number, even a little loss of mass will produce powerful energy!
Schematic diagram of uranium -235 fission
If so, the nuclear fission energy cliff is an excellent energy source, but the nuclear fission method is not only a loss of quality, but also a lot of pollution! The diagram of uranium -235 fission in the above picture shows that when a uranium -235 atom is bombarded by thermal neutrons, it will split into barium-14 1 and krypton -92, and 2-3 neutrons will be released! This neutron is very critical, and its function is as follows:
Nuclear fission reactors need thermal neutrons to maintain chain fission, because uranium -235 fission needs neutrons to maintain fission, while uranium -235 atoms will release 2-3 neutrons when fission, which means that neutron proliferation effect is to meet the needs of continuous fission. Just use moderator to slow down the fast neutrons of fission into slow neutrons, so that uranium -235 can easily absorb continuous fission!
Another problem is the harm of neutrons. Although there are neutrons in the nuclear components of our bodies, free neutrons are extremely harmful. They will directly damage DNA and cause secondary radiation. Moreover, they are not charged particles and cannot be shielded by magnetic fields. Only use thick lead plates or other materials that can block neutrons!
Uranium decay
These are the uses and hazards of neutrons, but there are not only neutrons in fission reactors, but also gamma rays that are very harmful. Of course, radiation is also indispensable. They will be produced in the process of fission and decay, because the decay chain of elements after nuclear fission will continue to produce these radiations, so nuclear fission will be very harmful if it is not protected!
Chernobyl nuclear accident
1On April 26th, 986, the No.4 reactor of Chernobyl nuclear power plant in Ukraine shut down a series of protective measures due to the operator's mistakes during the test. Eventually, the power of nuclear reactor increased greatly, and the emergency core cooling system, regional automatic control system and emergency shutdown system were also shut down. As a result, the pressure of the nuclear reactor increased greatly, and the first explosion directly blew a big hole in the shell of the nuclear reactor! And the second explosion directly blew up the core!
The exploded No.4 reactor
Radioactivity in high-concentration nuclear reactors is directly thrown into the atmosphere, which is aggravated by steam and burning smoke. Countless radioactive materials flowed through the upper atmosphere, covering parts of the former Soviet Union and most parts of Europe. This is the most harmful nuclear accident in history, and it is rated as the highest level 7 accident by the international nuclear event classification table!
On March 1 1, 1, 2065438, a nuclear accident caused by the 3 1 1 earthquake occurred in Fukushima Daiichi nuclear power plant, which resulted in equipment damage, core melting and release of a large amount of radioactive materials. In addition, a large amount of cooling water polluted by radioactive nuclear is discharged into the Pacific Ocean, and its deep-seated harm may be more serious than Chernobyl, because pollution is connected with the whole world.
Hydrogen bomb explosion is nuclear fusion, so will the runaway nuclear fusion reactor blow the earth to the sky?
We have seen the powerful harm of nuclear fission reactor leakage and know more about the power of hydrogen bombs. Although the nuclear fusion reactor has not yet been built, what should we do if the nuclear fission leakage of the nuclear fusion reactor is more dangerous than the hydrogen bomb? To know how powerful it is, we have to start with the principles of nuclear fusion and hydrogen bomb!
Fusion is simpler than fission, and it is Australian nuclear physicist Mark? The discovery of Europe is simply that two light nuclei combine to form a heavier nucleus, and mass defect will occur in the whole process, but its mass defect ratio is about 8- 10 times that of fission! So the power of hydrogen bomb is much greater than that of atomic bomb, but the real reason is not here!
Fusion process of deuterium and tritium
Nuclear fusion, which looks extremely simple, needs tens of millions to hundreds of millions of degrees of high temperature to achieve, and human beings can't reach the full temperature at all. So after the invention of the atomic bomb, scientists thought of using the explosion of the atomic bomb to realize the ultra-high temperature and high pressure environment! Of course, the model of hydrogen bomb detonation is very complicated. It is said that there are only two configurations in the world that can make hydrogen bombs explode, one is Taylor configuration and the other is Yumin configuration. No matter which mode, the hydrogen bomb is very powerful!
The nuclear charge of the atomic bomb has a critical mass, so the nuclear material to be fissile must be distributed in a complex structure, and as much charge as possible before the explosion is the key to fission (only one kilogram of the 20-kilogram charge of the Hiroshima atomic bomb participated in the fission, resulting in a quality defect of one gram, with a power of 20,000 tons of TNT equivalent)! Therefore, the equivalent of an atomic bomb is often capped, and it is difficult to have TNT equivalent of more than 500,000 tons! But hydrogen bombs don't have all bottlenecks, so the power of hydrogen bombs is almost unlimited.
Two typical structures of atomic bomb
The most powerful hydrogen bomb in the world was tested and exploded by the former Soviet Union in Xindi Island? Ivan the Great? Hydrogen bomb, the original explosion power is equivalent to 1 100 million tons of TNT, but scientists have found that the explosion area is inhabited by people through calculation, so reducing the charge will reduce the power to 50 million tons, and the actual power is about 58 million tons!
Big Ivan (Tsar Bamba) explosion scene
The fusion time of the nuclear charge of this hydrogen bomb is 38 nanoseconds, releasing 2 10000 megajoules of energy and producing a fireball with a radius of 4600 meters. The hot gas wave of the explosion is still fatal at a distance of 170 km. The electromagnetic pulse generated by the explosion caused the radio to be interrupted for more than an hour! Its power is more than 2.5 times that of the Tunguska Big Bang!
Will the nuclear fusion reactor blow over the earth out of control?
We have seen fission reactors out of control, and hydrogen bombs explode. So, is the fusion reactor out of control as dangerous as hydrogen bombs? International thermonuclear fusion reactor is an experimental reactor prepared by more than a dozen countries to break through commercial nuclear fusion. Its structure is Tokamak (typical magnetic constraint, satellite simulator is also magnetic constraint, and national ignition facility is inertial constraint)!
Tokamak structure
Because it is used to generate electricity, it is impossible to achieve fusion by atomic bomb explosion. Its principle is to confine the deuterium-tritium plasma in a vacuum chamber by using the super-strong magnetic field generated by superconducting magnets, and then make it reach 50 million to 100 million degrees by special heating method, so as to achieve the purpose of deuterium-tritium fusion!
Deuterium-tritium fusion can also produce uncontrollable neutrons, leading to element transmutation. Therefore, there is a first wall in the re-fusion reactor to prevent neutrons from escaping, and at the same time, the thermal radiation received by the first wall will be led out by the cooling pipe, and the heated water will form high-pressure steam to drive the steam turbine to generate electricity!
In the superconducting cavity of the tokamak, the intense plasma is controlled by the magnetic field formed by the super transformer, but it is extremely difficult to control the plasma, so the experiments in various countries are aimed at controlling the high-temperature plasma for a longer time, but even so, the plasma is still very easy to break. Once out of control, ultra-high temperature plasma will destroy the first wall, and ultra-high temperature plasma will continue to destroy superconducting cavity and other equipment. But it will not form a large-scale explosion!
Because it is not like a fission reactor, if it is out of control, it may form a runaway chain reaction (the control rod cannot be inserted to absorb neutrons, etc.). ), or a large number of decaying materials enter the atmosphere, the fusion reactor needs ultra-high temperature heating fusion under the constraint of magnetic field. Once this constraint condition is lost, the final plasma contains all its energy!
So in this state, its destructive power is extremely limited! The biggest possibility is that the fusion reactor is damaged, which requires a lot of money to maintain, but there will be no destructive damage like nuclear fission reactor, which may cause a little radiation impact of transmuted materials, but it is very limited!
So, don't worry, if the thermonuclear fusion reactor is out of control, it won't let the earth fly into the sky. Of course, although the principle of inertial confinement fusion reactor is somewhat different, it won't!