What is radiation and how do we measure it?

Atomic nuclei are made up of protons and neutrons. When protons and neutrons combine to form an atomic nucleus, the ratio of protons to neutrons creates either a stable or unstable nucleus.

An unstable nucleus gives off alpha particles (two protons and two neutrons), electrons, electromagnetic waves (gamma rays, X-rays, and neutrons), and changes into a stable nucleus. The alpha rays, electrons, gamma rays, X-rays, and neutrons that one nucleus gives off when it changes into another nucleus are called radiation. Radiation is much more dangerous than electromagnetic waves because it has more energy than the electrons circling around the nucleus.

Radiation occurs when an unstable atomic nucleus changes to a stable state.

When an element with an unstable nucleus gives off radiation and changes into another element, it is called radioactive decay. Depending on the degree of instability, radioactive decay takes different amounts of time. The time it takes for a certain amount of a radioactive element to decay and leave half of it behind is called the half-life.

The shorter the half-life, the more unstable the nucleus. Uranium-235, which is used as fuel for nuclear power generation, has a half-life of about 700 million years, and uranium-238, which is not used as fuel, has a half-life of about 4.6 billion years. These nuclei are very stable and do not decay easily.

However, when a neutron enters the nucleus, the ratio of protons to neutrons changes, and the level of instability increases, so it splits easily. The fission products of this fission are mostly very unstable radioactive elements.

These radioactive elements undergo multiple decay processes until they become stable elements. The intermediate products of this process are also unstable nuclei that are radioactive. There are more than 200 different types of radioactive substances produced during nuclear fission.

How do we measure the effects of radiation on the human body?

When these radioactive elements decay, they always produce radiation. Radiation has a lot of energy and can have a big impact on the human body. Therefore, it has become a very important issue to measure the intensity of radiation to determine how harmful it is to the human body.

The oldest way to measure the intensity of radiation is to measure how many radioactive decays occur in a second. If one radioactive decay occurs per second, that is, one dose of radiation per second, the intensity of radioactivity is called one becquerel (Bq). Becquerel is so small that we often use the unit curie (Ci), which actually represents 3.7×1010 Bq.

However, the energy of the radiation is more important than the number of radiation beams, so the intensity of the radiation is more about the energy absorbed than the number of beams. The most common unit for the energy of radiation is the gray (Gy). One Gy is the absorbed dose when a 1 kg object absorbs 1 J of energy from radiation. The unit of rad (rd; rad) is sometimes used to represent the absorbed dose, where 1 rd is 0.01 Gy.

The reason radiation is dangerous is because it ionizes atoms and molecules, so it is often better to express the degree to which the radiation ionizes matter. The degree of ionization is expressed as the amount of charge generated per unit mass (C/kg).

However, these units don’t give a good indication of how dangerous radiation is. Different types of radiation cause different degrees of biological damage even if the absorbed energy is the same. Therefore, to express the effect on living organisms, a weighting factor (QF) based on the type of radiation must be considered to determine the degree of damage.

QFs represent the degree of biological damage compared to an X-ray with an energy of 200 keV. The weighting factor depends on the type of radiation, as well as the energy of the radiation, the type of tissue exposed, and the type of biological effect of interest. In general, gamma rays have a QF of 0.5 to 1, beta rays (electrons) are 1, protons and neutrons are 2 to 10, and alpha rays are 10 to 20. A higher qualitative factor indicates a higher risk for the same energy.

The degree of damage that takes into account the weighting factors of radiation is called the equivalent dose, and the degree of risk to tissues in the body is called the effective dose. The equivalent dose or effective dose is expressed using the units of rem (rem) or sievert (Sv). One rem is 0.01 Sv.

Therefore, the quantity that represents how much damage you will suffer when exposed to radiation is the sievert (Sv). This is why radiation limits are all expressed in sieverts. The annual limit of radiation exposure from artificial sources for the general public is limited to 1 mSv. For those working in related industries, the annual limit is 20 mSv. An mSv is 0.001 Sv.

Radiation is dangerous, but you can’t avoid it

We are exposed to radiation in the natural environment. We receive about 0.37 mSv per year from radiation from space and about 2 mSv from natural radioactive elements in the earth’s crust, for a total of about 2.4 mSv per year. Of these, radon and its fission products receive the most radiation, amounting to 1.34 mSv.

The total amount of radiation received from artificial sources over the course of a year, including about 0.39 mSv from X-rays and 0.14 mSv from other medical uses, is about 0.67 mSv. Therefore, we receive about 3.1 mSv to 3.6 mSv of radiation per year from a combination of natural and artificial sources.

Radiation causes a number of damages to the human body. High-energy radiation damages DNA by ionizing DNA molecules. Damaged DNA can cause genes to mutate or cause cells to die. Mutations caused by DNA damage can lead to genetic defects and even cancer.

DNA damage and cell death can lead to a variety of diseases, including skin erythema and ulcers, cataracts, cloudy eyes, and organ failure. In addition, radiation ionizes water molecules, which are abundant in our bodies, to produce hydrogen ions and hydroxide ions. These ions can combine with many other molecules to create substances that can harm your health.

Radiation is dangerous, but it can’t be completely avoided. It’s safe to say that radiation is a part of our lives. The important thing is to make sure that you’re not exposed to enough radiation to harm your health.

However, in many cases, radiation that is harmful to your health cannot be prevented by your own efforts. There are a growing number of facilities that emit radiation, including nuclear power plants. We can only hope that as these facilities increase, so will national awareness of radiation and safety facilities.

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