Alpha-, gamma, beta radiation. Properties of particles alpha, gamma, beta

What is a radionuclide? Do not be frightened by this word: it simply means radioactive isotopes. Sometimes in a speech you can hear the words "radionucleide", or even less literary version - "radionucleotide". The correct term is the radionuclide. But what is radioactive decay? What are the properties of different types of radiation and how do they differ? About everything - in order.

Definitions in radiology

Ever since the explosion of the first atomic bomb, many concepts from radiology have undergone changes. Instead of the phrase "atomic boiler" it is customary to say "nuclear reactor". Instead of the phrase "radioactive rays" use the expression "ionizing radiation." The phrase "radioactive isotope" is replaced by "radionuclide".

Long-lived and short-lived radionuclides

Alpha-, beta- and gamma-radiation accompany the decay of the atomic nucleus. What is the half-life? The nuclei of radionuclides are not stable, which is why they differ from other stable isotopes. At some point, the process of radioactive decay starts. Radionuclides are converted into other isotopes, during which alpha, beta, and gamma rays are emitted. Radionuclides have a different level of instability - some of them disintegrate for hundreds, millions and even billions of years. For example, all isotopes of uranium that are found in nature are long-lived. There are also such radionuclides that disintegrate within seconds, days, months. They are called short-lived.

The emission of alpha, beta, and gamma particles accompanies not any decay. But in fact, radioactive decay is accompanied only by the release of alpha or beta particles. In some cases this process is accompanied by gamma rays. Pure gamma radiation in nature does not occur. The higher the decay rate of a radionuclide, the higher its radioactivity level. Some believe that there are alpha, beta, gamma and delta decays in nature. This is not true. Delta-decay does not exist.

Units of measurement of radioactivity

But how is this value measured? Measurement of radioactivity allows expressing the intensity of the decay in figures. The unit for measuring the activity of the radionuclide is Becquerel. 1 becquerel (Bq) means that 1 decay occurs in 1 sec. Once for these measurements, a much larger unit of measure was used: curie (Ki): 1 curie = 37 billion becquerels.

Naturally, it is necessary to compare the same mass of matter, for example, 1 mg of uranium and 1 mg of thorium. The activity of the taken unit of mass of a radionuclide is called specific activity. The longer the half-life, the lower the specific radioactivity.

What radionuclides are a big danger?

This is a rather provocative question. On the one hand, short-lived ones are more dangerous, because they are more active. But after their disintegration the very problem of radiation loses its relevance, while long-lived ones pose a danger for many years.

The specific activity of radionuclides can be compared with a weapon. Which weapons will be more dangerous: what makes fifty shots per minute, or what shoots once in half an hour? This question can not be answered - it all depends on the size of the weapon, how it is loaded, whether the bullet will reach the target, what will be the damage.

Differences between types of emissions

Alpha-, gamma and beta types of radiation can be attributed to the "caliber" of weapons. These emissions have both common and differences. The main common property - all of them are classified as dangerous ionizing radiation. What does this definition mean? The energy of ionizing radiation has an extraordinary power. When they get into another atom, they knock out an electron from its orbit. When the particle is emitted, the charge of the nucleus changes - a new substance is formed.

Nature of alpha rays

And the common thing between them is that gamma, beta and alpha radiation have a similar nature. Alpha rays were the first to be discovered. They were formed during the decay of heavy metals - uranium, thorium, radon. Already after the discovery of alpha rays, their nature was clarified. They turned out to be helium nuclei flying at great speed. In other words, these are heavy "sets" of 2 protons and 2 neutrons having a positive charge. In the air, alpha rays pass very little distance - not more than a few centimeters. Paper or, for example, the epidermis completely stops this radiation.

Beta radiation

Beta particles, discovered by the following, turned out to be ordinary electrons, but possessing enormous speed. They are much smaller than alpha particles, and also have a smaller electric charge. Beta-particles are easily penetrated into various materials. In the air, they cover a distance of several meters. They can be detained by the following materials: clothing, glass, thin metal sheet.

Properties of gamma rays

This type of radiation has the same nature as ultraviolet radiation, infrared rays or radio waves. Gamma rays are photon radiation. However, with an extremely high speed of photons. This type of radiation penetrates very quickly through the materials. To arrest it, lead and concrete are usually used. Gamma rays can travel thousands of kilometers.

Myth of danger

Comparing alpha, gamma and beta radiation, people usually consider gamma rays to be the most dangerous. After all, they are formed during nuclear explosions, overcome hundreds of kilometers and cause radiation sickness. All this is true, but it has no direct relationship to the danger of rays. Since in this case they speak about their penetrating ability. Of course, alpha, beta and gamma rays differ in this respect. However, the danger is assessed not by penetrating ability, but by the absorbed dose. This indicator is calculated in joules per kilogram (J / kg).

Thus, the dose of absorbed radiation is measured by a fraction. In its numerator is not the number of alpha, gamma and beta particles, namely energy. For example, gamma radiation can be hard and soft. The latter has less energy. Continuing the analogy with the weapon, you can say: the importance is not only the caliber of the bullet, it is important and what the shot is made of - a slingshot or a shotgun.