194
12 Health Hazards and Protection
12.6.3 Time
Time is an alternative method to minimize the dose-rate. A dose higher than the
maximum permissible level may be tolerated for a shorter duration, provided the
average dose for the period (e.g., one week), is below the maximum permissible
level. However, this should not become a regular practice but may be used when
other methods of shielding are unsuitable.
12.7 Instruments for Detection and Measurement
of Radiation
In a radiochemical laboratory, it is necessary to keep a continuous watch on the level
of activity due to radiations, so that if there is any sudden change in activity level in the
laboratory due to any accident or spillage etc., necessary precautions could be taken,
immediately. Moreover, after finishing the work in the radiochemical laboratory, it is
also necessary to ensure that the personnel is not carrying with him some radioactive
isotopes due to some contamination, because this will not only be dangerous to the
person, but also to the society as well. In addition to this, while working with γ -
source or neutron source, it is also necessary to get the information about the dose
being received. For this purpose, we need a device which can give an instantaneous
dose in terms of rad/hr received by the person. Finally, there is also a need to have
some knowledge of the accumulated dose due to various radiations received by the
personnel working in the laboratory over a period of week/months/year. For these
purposes, some special type of monitors are used. These are being discussed in this
section.
12.7.1 Portable Hand Monitor
The portable hand monitor usually consists of an ionization chamber designed to have
a response, which is approximately proportional to the dose in rad/hr. The portable
monitor operates usually with a battery operated valve voltmeter. This monitor is
used to measure the dose-rate during the dispensing of radioactive materials.
12.7.2 Pocket Dosimeter
A pocket dosimeter consists of a chamber containing a metalized quartz fiber, which
is charged to a fixed potential. Any radiation passing through it causes ionization,
which allows the charge to leak away. The movement of the fiber indicates the inte-
12 Health Hazards and Protection
12.6.3 Time
Time is an alternative method to minimize the dose-rate. A dose higher than the
maximum permissible level may be tolerated for a shorter duration, provided the
average dose for the period (e.g., one week), is below the maximum permissible
level. However, this should not become a regular practice but may be used when
other methods of shielding are unsuitable.
12.7 Instruments for Detection and Measurement
of Radiation
In a radiochemical laboratory, it is necessary to keep a continuous watch on the level
of activity due to radiations, so that if there is any sudden change in activity level in the
laboratory due to any accident or spillage etc., necessary precautions could be taken,
immediately. Moreover, after finishing the work in the radiochemical laboratory, it is
also necessary to ensure that the personnel is not carrying with him some radioactive
isotopes due to some contamination, because this will not only be dangerous to the
person, but also to the society as well. In addition to this, while working with γ -
source or neutron source, it is also necessary to get the information about the dose
being received. For this purpose, we need a device which can give an instantaneous
dose in terms of rad/hr received by the person. Finally, there is also a need to have
some knowledge of the accumulated dose due to various radiations received by the
personnel working in the laboratory over a period of week/months/year. For these
purposes, some special type of monitors are used. These are being discussed in this
section.
12.7.1 Portable Hand Monitor
The portable hand monitor usually consists of an ionization chamber designed to have
a response, which is approximately proportional to the dose in rad/hr. The portable
monitor operates usually with a battery operated valve voltmeter. This monitor is
used to measure the dose-rate during the dispensing of radioactive materials.
12.7.2 Pocket Dosimeter
A pocket dosimeter consists of a chamber containing a metalized quartz fiber, which
is charged to a fixed potential. Any radiation passing through it causes ionization,
which allows the charge to leak away. The movement of the fiber indicates the inte-