662 Chapter 11. Dosimetry and Radiation Protection
framework for the radiation safety personnel to monitor the workers more closely
and take safety precautions accordingly. The usability of ALARA principle becomes
evident when one considers the possibility that a worker gets a high dose within a
short period of time, say a month, such that the yearly dose does not get exceeded.
This can be problematic since continuing working in such an environment may prove
to be harmful due to the increased probability of damage. For such situations, most
organizations define different ALARA levels. Two level systems are fairly common
in which if the dose received by the worker exceeds the first level the environment
is surveyed for the conditions and the worker is put on an aggressive monitoring
routine. In case the worker exceeds the level 2 she or he may then be barred from
working in any radiation environment for an extended period of time. Most of the
time ALARA levels are defined according to the dosimeter readout periods. The
dosimeter badges are generally read out every one or two months, at which time the
dose is monitored according to the ALARA guidelines specific to the organization.
Table 11.6.2 gives an example of a three level ALARA guideline for the whole body
dose for radiation workers.
11.7RadiationProtection...........................
Though radiation has been found to be extremely useful in different fields, its use
has extreme radiation hazards associated with it. The protection of personnel and
equipment from harmful effects of radiation is of primary concern in any radiation
environment. In this section we will concentrate on discussion of radiation protection
for personnel. The issue of radiation damage to materials has already been discussed
in various chapters in this book.
11.7.AExposureReduction
In many situations it is extremely difficult, if not impossible, to completely elimi-
nate the possibility of radiation exposure to personnel. However, one can work on
minimizing the exposure using some simple techniques mentioned in the following
sections.
A.1 Time...............................
Low level dose integrated over a long period of time can cause significant harm to
personnel. The dose can therefore be minimized by carefully planning the activities
such that the exposure time is as short as possible. The workers in radiation envi-
ronments are required to wear a dosimeter to record the dose. After some time the
dosimeter is read out through a reading device and the exposure level is compared
with the limit set by the corresponding authority. In case the limit has been ap-
proached the worker is not allowed to enter any other radiation environment for a
specific period of time.
A.2 Distance.............................
Radiation follows inverse square law unless there is significant scattering and ab-
sorption in the medium. This law states that the radiation flux is proportional to