Regional Basic Professional Training Course in Korea

❙ 109 ❙
2. Radiation Protection
radiation worker in a national laboratory or an industrial setting (e.g., pharmaceutical
company, nuclear power plant, or X‐ray diffraction application) should examine his/her
particular workplace to establish a practical plan incorporating the distance principle.
2.8.3. Shielding
The third and last type of protection against ionizing radiation consists of placing a
barrier, or shield, between the radiation and the rest of the world. This barrier takes many
different forms.
To shield from alpha particles, a thin sheet of paper is generally sufficient. For beta
particles having those energies commonly encountered, a few millimeters of aluminum or
a similar material is sufficient. When dealing with photons, the problem is not so simple.
As with distance, no amount of shielding eliminates all photons. In addition, shielding
has inherent problem in terms of weight and cost. It is only practical to surround a source
of ionizing radiation with so much shielding. For example, when transporting a
radionuclide only so much shielding can be used before the package can be moved only
with a forklift. Equally, an X‐ray machine can be surrounded by just so much shielding
before the cost of building the containing wall becomes prohibitive. For these reasons, the
effective/equivalent dose limits are used to set standards of irradiation; then distance and
shielding are used together to meet these standard.
Note that the discussion of shielding against photons given in this section is purely
theoretical. It is intended only to elucidate the concepts described herein.
2.8.3.1. Half‐Value Layer
To calculate the amount of shielding required, a concept known as the half‐value