What is a radionuclide? No need to be afraid of this word: it simply means radioactive isotopes. Sometimes in a speech one can hear the words “radionuclide”, or an even less literary version - “radionucleotide”. The correct term is a radionuclide. But what is radioactive decay? What are the properties of different types of radiation and how do they differ? About everything - in order.
Radiology Definitions
Since the time when the first atomic bomb exploded, many concepts from radiology have undergone changes. Instead of the phrase "nuclear boiler" it is customary to say "nuclear reactor". Instead of the phrase “radioactive rays” they 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? Nuclei of radionuclides are not stable - this is what they differ from other stable isotopes of. At a certain moment, the process of radioactive decay starts. Radionuclides in this case turn into other isotopes, during which alpha, beta and gamma rays are emitted. Radionuclides have different levels of instability - some of them decay over hundreds, millions, and even billions of years. For example, all uranium isotopes that occur in nature are long-lived. There are also radionuclides that disintegrate within seconds, days, months. They are called short-lived.
The release of alpha, beta and gamma particles does not accompany 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 does not occur in nature. The higher the decay rate of a radionuclide, the higher its level of radioactivity. Some people believe that alpha, beta, gamma, and delta decay exist in nature. This is not true. Delta decay does not exist.
Radioactivity units
However, in what is this quantity measured? Measurement of radioactivity allows you to express the decay intensity in numbers. The unit of measurement of radionuclide activity is becquerel. 1 becquerel (Bq) means that 1 decay occurs in 1 second. Once upon a time, a much larger unit of measurement was used for these measurements - curie (Ki): 1 curie = 37 billion becquerels.
Naturally, it is necessary to compare the same masses of matter, for example 1 mg of uranium and 1 mg of thorium. The activity of a taken unit of mass of a radionuclide is called specific activity. The longer the half-life, the lower the specific radioactivity.
What radionuclides are most dangerous?
This is a rather provocative question. On the one hand, short-lived are more dangerous, because they are more active. But after all, after their decay, the very problem of radiation loses its relevance, while long-living people pose a danger for many years.
The specific activity of radionuclides can be compared with weapons. Which weapon will be more dangerous: that which makes fifty shots per minute, or that that shoots once every half an hour? This question cannot be answered - it all depends on what the caliber of the weapon is, what it is charged with, whether the bullet will reach the target, what the damage will be.
Differences between types of emissions
Alpha, gamma and beta types of radiation can be attributed to the "caliber" of the weapon. These radiations have both general and differences. The main common property is that all of them are classified as dangerous ionizing radiation. What does this definition mean? The energy of ionizing radiation has extraordinary power. Getting into another atom, they knock an electron from its orbit. When a particle is emitted, the charge of the nucleus changes — a new substance is formed.
The 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. After the discovery of alpha rays, their nature was clarified. They turned out to be flying with great speed helium nuclei. In other words, these are heavy “sets” of 2 protons and 2 neutrons with a positive charge. Alpha rays travel a very short distance in the air - no 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 with tremendous speed. They are much smaller than alpha particles, and also have a lower electric charge. Beta particles easily penetrate various materials. In the air they cover a distance of several meters. The following materials can detain them: clothing, glass, thin metal sheet.
Gamma ray properties
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 materials very quickly. To delay it, lead and concrete are usually used. Gamma rays can travel thousands of kilometers.
The 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 is not directly related to the danger of rays. Since in this case they are talking specifically about their penetrating ability. Of course, alpha, beta, and gamma rays are different in this regard. However, the hazard is not assessed by penetration, but by the absorbed dose. This indicator is calculated in joules per kilogram (J / kg).
Thus, the dose of absorbed radiation is measured in fractions. Its numerator is not the amount of alpha, gamma and beta particles, but energy. For example, gamma radiation can be hard and soft. The latter has less energy. Continuing the analogy with weapons, we can say: not only the caliber of the bullet matters, it is also important whether the shot is fired - from a slingshot or from a shotgun.