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4) radiation affects not only currently a living organism, but also on his
descendants (genetic effect);
5) effectiveness of radiation depends on the frequency of its action;
6) various human organs and organisms to respond differently to radiation.

According to the Law of Ukraine "On Protection of Rights of ionizing
radiation" and Standards radiation safety of Ukraine - NRBU-97 dose limit
personal exposure (the maximum allowable level of the individual effective dose of
radiation, exceeding the required measures to protect) assigned to the following
categories (Table 13.5):
- Staff (Category A - persons permanently or temporarily working directly with
sources of ionizing radiation, category B - Persons who are not directly engaged in
work with ionizing radiation, but due to the location of jobs in areas and at industrial
sites at 'objects with radiation and nuclear technologies may receive additional
exposure).
- Population (category C).
The main dose limits personal exposure of the population should not exceed 1
mSv effective dose per year.

Table 13.5 - Limits dose (mSv / year)
Category of persons exposed to radiation
А B C
Effective dose limit LDE
20 2 1
Limits of equivalent doses of external irradiation
For the lens of the eye 150 15 15
For the skin 500 50 50
For hands and feet 500 50 -

13.5 Limiting Exposure

There are three standard ways to limit exposure:
1. Time: For people who are exposed to radiation in addition to natural
background radiation, limiting or minimizing the exposure time will reduce the dose
from the radiation source.
2. Distance: Radiation intensity decreases sharply with distance, according to
an inverse-square law (in an absolute vacuum).
3. Shielding: Air or skin can be sufficient to substantially attenuate low-
energy alpha and beta radiation. Barriers of lead, concrete, or water give effective
protection from more energetic particles such as gamma rays and neutrons. Some
radioactive materials are stored or handled underwater or by remote control in rooms
constructed of thick concrete or lined with lead. There are special plastic shields that
stop beta particles, and air will stop most alpha particles. The effectiveness of a
material in shielding radiation is determined by its half-value thicknesses, the

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