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Dosimeters and radiometers

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Concepts, terms and definitions of dosimetry (Ryabov NV)

Concepts, terms and definitions of dosimetry (Ryabov NV)Enlarge


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Radioactivity existed on earth and in the surrounding area at all times. This is one of the properties of matter. Radioactive radiation is a consequence of radioactive transformations of elements in the same way as, for example, thermal radiation and light are in most cases due to chemical reactions - combustion.When exposed to radiation did life originate on Earth, radiation exposure were our ancestors, we are exposed to will be subject to our posterity.

Natural, independent of human radioactive radiation from radiation arriving at Earth from space, and radioactivity of certain elements that make up the objects around us, in the air in the body of the man himself (radon, thorium, uranium, potassium, radium, etc. ..)This natural background radiation, such as a natural effect, which is adapted to the human body, like light, the gravitational force of gravity, ambient temperature, etc. And just as in the case of light, gravity, heat, there are certain levels of exposure at which the radioactive radiation does not affect the condition of the body, there are levels where it is harmful and even fatal. Under certain conditions, may also therapeutic effects of radiation on the body (such as killing harmful to the body of cancer cells, increasing the functional activity of radon baths at the reception).

The impact of radiation is determined by its composition, particle energy, power flow. To assess the effects of radiation on the human body uses the concept of equivalent absorbed dose - the amount of energy absorbed per unit mass of the substance of the body, taking into account the biological hazards of this type of radiation. The unit of absorbed dose is - Sievert (Sv, Sv).

To characterize the level of gamma radiation, the most penetrating radiation and makes the main contribution to the whole body irradiation, also applies the concept of dose in the air, for which has its own unit - Roentgen (R). One Sievert is equal to about 100 X-rays. Since these units are quite large compared to the conventional natural effects, are usually the values ​​that make up one-thousandth (milli) or one-millionth (micro) share Sievert or X-rays.

1 Sv = 1000 mSv = 1000000 micro Sv

1 R = 1000 mR  = 1000000 microR

Sievert and X-rays - the characteristics of the total (integrated) effects. To estimate the rate of dose accumulation uses the concept of dose rate - the amount of energy absorbed per unit time (hour, minute, second). Units of dose rate - Sv / h, mSv / h, P / h, mR / h, etc.

Beta radiation (in the natural radioactivity of the human, it is a major source of potassium) is characterized by the capacity of the particle flux. Unit of measure - the number of particles passing per unit time through unit surface area (1 cm2): particles / (cm2 min) or part / (cm2 sec).

To characterize the power of a radioactive source accepted notion - the activity. Activity unit - Becquerel (Bq). 1 Bq activity means that the source is a radioactive transformation per second. Previously used one Curie. One Curie - is the activity of one gram of radium.The relationship between the Curie and Becquerel quite complicated:

1 Curie = 3.7 * 1010 Bq (37 billion Bq).

To imagine what these units, we give some examples. Typically, the external background is human exposure at the 1 ... 2 mSv per year, with about two thirds of this value is due to sources located within the person (internal radiation). At the same dose of external gamma radiation is 10 ... 15 mR / h. This value is the average and can vary by several times. So, above sea level, it is 5 ... 7 mR / h in mountainous regions - up to 50 ... 60 mR / h, in the Caucasian Mineral Waters - 20 ... 30 mR / h in Moscow - 10 ... 20 mR / h. The dose rate varies by several times depending on season, time of day, weather conditions. Thus, over 70 years of life, a person receives a dose of 7 to 14 X-rays, although there are areas (highlands), where this value reaches 35 ... 40 R. Contained in the human potassium has an activity of about 30 Bq, the natural activity of 1 kg of meat - 50 ... 60 Bq, 1 liter of milk - 10 ... 20 Bq, 1kg apricots - to 200 Bq, 1 kg of potassium fertilizer - 5 ... 10 000 Bq.


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