12.1 Basics and Guidelines
104
Section 12 Radiation Protection
12.1 Basics and Guidelines
The radioactive isotopes used for bulk flow measurements emit
gamma radiation. Gamma radiation consists of electromagnetic
waves, i.e. it is a type of radiation which resembles light, but has a
much higher energy, so that it can pass through matter. This high-
energy radiation is hazardous to living beings; a it can damage
cells and cause mutations. To minimize this hazard, one must be
extremely careful when handling radioactive substances.
The radioactive sources used for density measurements are usually
sealed sources, i.e. the actual radioactive substance is surrounded
by at least one, often several sealed layers made of stainless steel,
each of which is checked individually for leaks. Another check en-
sures that no radioactive particles are deposited on the surface of
the capsule. The user will receive an official certificate specifying
these features of the radioactive source.
In order to prevent adverse health effects caused by working with
radioactive substances, limits for the maximum permissible radia-
tion exposure of operating personnel have been agreed upon on an
international level. Appropriate measures in designing the shield-
ings and arranging the measuring system at the measuring loca-
tion will ensure that the radiation exposure of the personnel will
remain below the maximum permissible value of 5 mSv (500
mrem) per year.
A Radiation Safety Officer has to be appointed who is re-
sponsible for all questions relating to radiation protection.
The Radiation Safety Officer will monitor handling of the radiomet-
ric measuring system and, if necessary, formalize the safeguards
and any special precautions applicable to a given establishment in
formal procedural instructions, which in special cases may serve as
a basis for radiation protection guidelines.
These may stipulate that access to the vessel shall only be permit-
ted after the active beam is shielded. Radiation protection zones
outside the shielding must be - if they are accessible - marked and
guarded.
These instructions should also include checks of the shutter device
of the shielding and measures for serious operational trouble -
such as fire or explosion.
Any special event has to be reported to the Radiation Safety
Officer immediately. He will then investigate any damage and
immediately take suitable precautions if he detects defects that
may adversely affect the operation or safety of the system.
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