Lead clothing is a kind of clothing that can effectively shield radiation. When doing some radioactive tests, doctors may use lead clothes to protect the non-examined parts so as not to damage important organs.
There are three kinds of nuclear radiation, namely, alpha rays, beta rays and gamma rays.
The essence of (1)α -ray is helium nucleus, which has two unit positive charges and a large mass, so it is easy to be shielded, and a blank sheet of paper can completely shield it.
(2) The essence of β -ray is electron flow, with unit negative charge and small mass. Because conventional substances are composed of electrons inside and outside the nucleus, beta rays can also be easily shielded, and air or ordinary metal with a thickness of several centimeters can be completely shielded.
(3) Gamma rays are essentially high-energy photons with no charge, very small dynamic mass and strong penetration.
Therefore, among the three kinds of nuclear radiation, gamma rays are the most dangerous and will cause serious irreversible damage to human cells. In addition, neutron radiation is deadly.
In order to shield gamma rays and neutron radiation, it is necessary to use substances that can absorb rays. In essence, any substance has the probability of absorbing radiation, but the ability to absorb radiation varies greatly.
For an atom, the larger the nucleus inside the atom, the more electrons outside the nucleus, and the easier it is to block the propagation of gamma rays and neutron radiation at the same thickness. Lead is a non-radioactive element with the largest atomic number, and its density is as high as 1 1.33 g/cm3, so it can effectively absorb gamma rays and neutron radiation.
Uranium has a higher atomic number and higher density, which can better absorb gamma rays and neutron radiation, but uranium itself will decay, so it is not suitable for shielding nuclear radiation; Some precious elements, such as gold and platinum. The density of lead is higher than that of lead, but they are too expensive to be used for shielding radiation in a large area.
Concrete is also an effective material for shielding gamma rays and neutron radiation, so in important military places, buildings are wrapped in thick concrete, and important underground rooms are protected by tens of meters thick concrete.
Many things can block nuclear radiation, even a piece of paper. Not all nuclear radiation needs to be blocked by lead.
Lead is mainly used to block gamma rays (gamma rays), which are high-energy rays and belong to the category of electromagnetic waves. When it comes into contact with an atom, it is easy to cause the electrons of the atom to gain energy and then run away. This process is called ionization. Lead has a high atomic density and high atomic number (that is to say, it has many electrons), so lead becomes a good barrier to block gamma rays, which is very suitable for scattering gamma rays or X rays to prevent them from causing harm to human body.
But the types of nuclear radiation are not only gamma rays, but also other nuclear radiation. Some of these radiations can be blocked by a piece of paper, but others need thick cement to block them, not lead. Because lead is not easy to use at this time.
To understand why, we need to know something about nuclear radiation. Then you need a little more patience to read the following words.
What exactly is nuclear radiation?
Illustration: Nuclear radiation is produced in the process of atomic decay, and heavy elements spontaneously become relatively light elements.
Until about 100 years ago, physicists accidentally discovered that some elements were unstable. They magically changed from one element to another, just like the scientific version of alchemy. Of course, they did not change from brass to gold, on the contrary, they changed from "gold" to "brass"! The law of this change always changes from heavier element atoms to lighter element atoms! So I just said that this change is from gold to brass, because gold atoms are heavier than copper atoms. Of course, don't worry about your gold bars, rings and earrings They are very stable, will not change this element, and certainly will not release harmful nuclear radiation.
Nuclear radiation is the energy and particles released in the process of changing heavy elements into light elements, which constitutes nuclear radiation.
Elements with this property are also called radioactive elements. The change of radioactive elements is called radioactive decay. Uranium is the best example of this element. It is the heaviest radioactive element in nature. All elements heavier than uranium are unstable and radioactive.
Radioactive decay is a natural process. Atoms of radioisotopes spontaneously decay into another element through one of three common processes:
In this process, four different kinds of radiation will be produced:
First of all, the natural decay of radioactive atoms is a part of nature, so they are "natural", but all radioactive elements are potentially dangerous to living things. Alpha particles, beta particles, neutrons and gamma rays are all called ionizing radiation. This is because when they collide with atoms, the electrons around the nucleus can be knocked away and the electrons run away. This process is called ionization, just like a wife running away. This will make our cells in a mess, leading to gene mutation or direct death.
How to stop nuclear radiation
Alpha particles are very large and are essentially helium nuclei moving at high speed, which are easily blocked. In fact, only a piece of paper or a few centimeters of air is enough to stop it. If you lose kinetic energy, you will lose your ability to harm the human body. Therefore, only the nuclear radiation of alpha particles is produced, and as long as you are a little farther away from it, the impact on the human body is not great.
Illustration: Particles can't even penetrate a piece of paper or a few centimeters of air.
Description: It is because this thing is safe. Therefore, the most commonly used smoke alarm uses the radioactive isotope americium 24 1, which can only release alpha particles. The alpha particles it produces can ionize air, and these ionized air are attracted by the positive and negative electrodes and hit the positive and negative electrodes, resulting in a weak current. If smoke enters the ionization chamber, it will neutralize the ionized air, and when the current drops, the smoke alarm will start to alarm.
But if you inhale or eat this radioactive element, it is dead. At this time, high-speed alpha particles attack you directly from the body, and you may get cancer. The most notorious element is radioactive radon, which is a gas. After inhaling it, the alpha particles released by it directly bombard your lung cells, which may lead to lung cancer. Non-smokers suffer from lung cancer, and radon may be the potential culprit. But some places still use radioactive radon spring as a selling point to attract tourists. Welcome to take a bath. In my opinion, this is death.
The essence of beta particles is high-energy electrons, which are much smaller than particles, so they have stronger penetrating power. But after all, electrons still have solid subatomic particles, so a piece of aluminum foil or plexiglass is enough to stop them. In fact, the old traditional TV screen was developed by bombarding phosphors with high-speed electrons, that is, artificial nuclear radiation. Traditional TV sets have no direct impact on human health except for damaging eyesight. As for being made an idiot by TV advertisements, watching TV with fried chicken and beer has nothing to do with high-speed electronics itself. But if you eat or inhale radioactive isotopes that can release beta particles, you are really dead.
The ranges of γ -rays and X-rays overlap, but simply speaking, they are high-energy X-rays, and their penetrating power far exceeds that of α-particles and β-particles, so lead is needed to stop them.
Illustration: Neutron-induced nuclear fission is the principle of atomic bomb and current nuclear power plant operation. In this process, fission atoms will release more neutrons, and if conditions are right, fission can continue.
Neutrons lack charge, so high-speed neutrons have strong penetration. The best way to stop high-speed neutrons is to use extremely thick concrete layers or liquids such as water and fuel oil to stop them. At present, nuclear power plants use neutrons to hit the nuclei of heavy elements to achieve nuclear fission and release energy, and the ways to prevent these high-energy neutrons from causing biological damage are water, oil and thick concrete layers.
Illustration: Three schemes for blocking high-energy fast neutrons.
1. First, cadmium plate shielding, then lead shielding, and finally the aqueous solution containing boric acid.
2. First shield with cadmium plate, then shield with lead, and finally shield with concrete.
3. Plug with water first, and then plug with cadmium plate to solve the problem. This is the simplest and cheapest solution.
Illustration: China's third generation commercial large-scale commercial PWR nuclear power plant, a nuclear reactor immersed in high-pressure water.
During the Cold War, the United States and the Soviet Union thought that developing neutron bombs (a small hydrogen bomb with low equivalent) and killing armored armed personnel by a large number of high-speed neutrons and gamma rays was the best choice for destroying tanks and armored vehicles on a large scale.
Illustration: neutron bomb test
Neutron bombs kill far more than other weapons. In addition, the interaction between neutrons and armor will make the armor radioactive and temporarily unusable (usually 24-48 hours). For example, there is depleted uranium in M- 1 tank armor, which can undergo rapid fission after being bombarded by neutrons and become highly radioactive substances.
Illustration: the slogan in the anti-nuclear war movement is against the development of new nuclear weapon neutron bombs. The first neutron bomb joined the U.S. arsenal in 1974.
All energy expressions in the world are realized by electromagnetic waves, and nuclear radiation is also an electromagnetic wave, which is produced by nuclear changes of atoms, mainly including three kinds of rays: α, β and γ.
How do we stop these rays?
In fact, any object can, but the blocking ability is different. For example, the shielding effect of 1mm lead plate is equal to 6mm iron plate and 12cm thick solid brick block.
The radiation barrier around the nuclear power plant is not made of lead, but concrete. As long as it is thick enough, any light will be blocked even if it has strong penetration ability.
Why is the light blocked?
Everything is made up of atoms, and photons representing radiant energy will be absorbed by these atoms when they pass through the "atomic array" of matter. There are three effects in this process: photoelectric effect, Compton effect and electron pair effect.
Briefly explain these three effects:
Photoelectric effect: photons transfer energy to extranuclear electrons and disappear by themselves;
Compton effect: photons collide with electrons, and some energy is transferred to electrons, which makes electrons recoil, while the energy and propagation direction carried by photons themselves will change;
Electron pair effect: When photons pass through atoms, they are attracted by the coulomb force of the nucleus and transformed into 1 positrons and 1 negative electrons, which are quickly annihilated.
So why lead?
Because the density of lead is high, that is, the number of protons and electrons in the atoms inside lead is dense enough, it is difficult to pass through.
Then why not other denser substances?
Other high-density substances are either very difficult to obtain or very precious (such as gold). In contrast, lead is the best choice.
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Lead shielding refers to the use of lead as radiation protection to reduce the effective dose to people or objects. Because of its high density and high atomic number, lead can effectively attenuate some kinds of radiation. In principle, it is effective for shielding gamma rays and x-rays.
The high density of lead is caused by the combination of its high atomic mass and its relatively small bond length and atomic radius. High atomic mass means that more electrons are needed to maintain neutral charge and small atomic radius binding length, which means that many atoms can be assembled into specific lead structures. Because of its density and a large number of electrons, lead is very suitable for scattering X-rays and γ-rays. These rays form photons, which are bosons, and when they come into contact with electrons, they are given strong penetrating power. Without lead shielding, electrons in the human body will be affected, which may damage human DNA and lead to cancer. When radiation tries to pass through lead, the electrons of lead absorb and scatter energy. However, lead will eventually degrade due to exposure to energy. However, lead is not effective for all types of radiation. High-energy electrons (including neutron radiation) may cause bremsstrahlung, which is more harmful to tissues than the original radiation. In addition, lead is not a particularly effective neutron radiation absorber.
Lead is used to shield X-ray machines, nuclear power plants, nuclear laboratories, military equipment and other places where radiation may be encountered. There are many kinds of shielding that can be used to protect people, as well as to shield equipment and experiments. Personal protection includes lead clothing (such as X-ray protective clothing used in dental surgery), protective screen and lead gloves. Laboratory equipment also has various shielding devices, including structures made of lead blocks and thick containers for storing and transporting radioactive samples.
Suspected to be blocked! Is it because you were detained? This science is rigorous enough.