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thickness of material that reduces the radiation by half. This value is a function of the
material itself and of the type and energy of ionizing radiation.

Some generally accepted thicknesses of attenuating material are 5 mm of aluminum for most
beta particles, and 3 inches of lead for gamma radiation.

The use of protective shielding based on the properties of materials and
substances depending on the thickness of absorbing radiation. The weakening of
ionizing radiation using shields characterized by exponential law:

І  І 0 e   x  , (13.1)
х
where I0 - the intensity of radiation in the absence of the shield;
Ix - the intensity of radiation in the presence of the shield;
μ - coefficient of weakening ray by the shield;
x - thickness of the shield.
The effective half-life of radioactive substances from the human body - time
during which the amount of radioactive element decreases by half due to radioactive
decay and biological excretion:

Т Т 
Т  5 , 0 b , (13.2)
еf
Т 5 , 0  Т b
where T 0, 5 - half-life - the time at which half the atoms decays of radioactive
elements;
Tb - the biological half-life period - the time during which the amount of
radioactive element decreases by half due to physiological exchange.
Half-life is determined by the law of natural decay of radioactive atomic
nuclei:
N  N 0 e   t  , (13.3)
where N, N0 - respectively the number of nuclei in this volume of material at time t
and t0;
-1
λ - decay constant,с .

Revision Questions

1) Explain the different types of ionizing radiation.
2) Doses of ionizing radiation and their units of measurement.
3) The quality and radiation risk factors of ionizing radiation.
4) Natural sources of ionizing radiation?
5) Name the basic sources of ionizing radiation in the oil and gas sector.
6) Different types of protection against ionizing radiation?
7) The standardization of radiation safety?

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