What is a radionuclide? There is no need to be afraid of this word: it simply means radioactive isotopes. Sometimes in speech you can hear the words "radionucleide", or even less literary version - "radionucleotide". The correct term is 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
Since the explosion of the first atomic bomb, many concepts in radiology have changed. Instead of the phrase "atomic boiler" it is customary to say "nuclear reactor". Instead of the phrase "radioactive rays" the expression "ionizing radiation" is used. The phrase "radioactive isotope" was replaced by "radionuclide".
Long-lived and short-lived radionuclides
Alpha, beta and gamma radiation accompany the process of decay of the atomic nucleus. What is a periodhalf-life? The nuclei of radionuclides are not stable - this is what distinguishes them from other stable isotopes. At a certain point, the process of radioactive decay starts. Radionuclides are then converted 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 naturally occurring uranium isotopes are long-lived. There are also radionuclides that decay 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 occurs 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 believe that alpha, beta, gamma and delta decay exist in nature. This is not true. Delta decay does not exist.
Radioactivity units
However, how is this value measured? The measurement of radioactivity allows the rate of decay to be expressed in numbers. The unit of measurement of radionuclide activity is becquerel. 1 becquerel (Bq) means that 1 decay occurs in 1 sec. Once upon a time, these measurements used a much larger unit of measure - the curie (Ci): 1 curie=37 billion becquerels.
Of courseit is necessary to compare the same masses of a substance, for example, 1 mg of uranium and 1 mg of thorium. The activity of a given unit mass of a radionuclide is called specific activity. The longer the half-life, the lower the specific radioactivity.
Which radionuclides are the most dangerous?
This is a rather provocative question. On the one hand, short-lived ones are more dangerous, because they are more active. But after all, after their decay, 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 to weapons. Which weapon would be more dangerous: the one that fires fifty shots per minute, or the one that fires once every half an hour? This question cannot be answered - it all depends on the caliber of the weapon, what it is loaded with, whether the bullet will reach the target, what the damage will be.
Differences between types of radiation
Alpha, gamma and beta types of radiation can be attributed to the "caliber" of weapons. These radiations have both common 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 is extremely powerful. When they hit another atom, they knock an electron out of its orbit. When a particle is emitted, the charge of the nucleus changes - this creates a new substance.
Nature of alpha rays
And the common thing between them is that gamma, beta and alpha radiation have a similar nature. by the mostalpha 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 that have a positive charge. In the air, alpha rays travel a very short distance - no more than a few centimeters. Paper or, for example, the epidermis completely stops this radiation.
Beta radiation
Beta particles, discovered next, turned out to be ordinary electrons, but with great speed. They are much smaller than alpha particles and also have less electrical charge. Beta particles can easily penetrate various materials. In the air, they cover a distance of up to several meters. The following materials can delay them: clothing, glass, thin metal sheet.
Properties of gamma rays
This type of radiation is of 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 generally consider gamma rays to be the most dangerous. After all, they are formed during nuclear explosions, overcome hundreds of kilometers andcause radiation sickness. All this is true, but it is not directly related to the danger of rays. Since in this case they are talking about their penetrating ability. Of course, alpha, beta, and gamma rays differ in this regard. However, the danger is assessed not by the penetrating power, but by the absorbed dose. This indicator is calculated in joules per kilogram (J / kg).
Thus, the dose of absorbed radiation is measured as a fraction. Its numerator contains not the number 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 what the shot is fired from - from a slingshot or from a shotgun.
