Ionizing Radiation in the Lab Ð a Glowing Prospect
Ionizing radiation, in different forms, are the result of unstable nuclei.
Such nuclei generally emit particles or rays that knock out electrons on the
atoms they hit, thus forming ions. These generally show up in four different
forms:
- Alpha Particles Ð The naked helium atom! Alpha particles are composed
of two neutrons and two protons or the basic helium nucleus. These particles
are the result of degradation of radio isotopes of heavy elements like uranium
and radium. The penetrating power of these particles is extremely limited
at best. Skin is a sufficient barrier to guard against infusion.
- Beta Particles Ð These are particles or electrons that originate in the
nucleus of radioisotopes. Because of their relatively small size and high
energy, most beta particles can penetrate skin. Low energy beta particles
have difficulty penetrating skin, but do present an internal hazard. High-energy
beta particles can penetrate living tissue.
- Gamma Rays Ð Gamma rays are not particles but photons. The rays are high
energy and therefore, have high penetrating power. Lead shielding can provide
protection.
- X-Rays Ð X-rays are similar to gamma rays. However, where gamma rays are
naturally occurring in origin, X-rays are artificially generated. This is
achieved by metal targets being bombarded with high-energy electrons in
a vacuum. X-rays, like gamma rays are a serious hazard resulting from their
penetrating power.
The Nuclear Regulatory Commission (NRC) has established Basedose limits for
different levels of ionizing exposure. These are published in the Code of
Federal Regulations (CFR 20). Limits are generally set at 5000 mREM/year for
whole body exposure and 30,000 mREM/year for skin of the whole body. Any sealed
source of radiation exceeding one milliCurie must be registered with the government.
In order to protect students at the high school level, radioactive sources
should be mounted in sealed discs. Teachers must be very careful that the
disks are not damaged in any way. None of these discs should exceed 1.0µCI.
The University of Illinois developed the following Laboratory Procedures
or protocols for dealing with radioactive materials. Teachers might want to
consider adopting these for their science classes when using radioactive materials.
- To prevent accidental entry of radioactive materials into the body, high
standards of cleanliness and good housekeeping must be maintained in all
laboratories where radioactive materials are present and/or used.
- Visitors are not allowed without approval of the chemical hygiene officer
or school system safety compliance officer.
- Wash hands and arms thoroughly before handling any object which goes to
the mouth, nose, or eyes (e.g. cosmetics, foods). Keep fingernails short
and clean.
- Eating or drinking in laboratories which deal with radioactive materials
is unsafe and forbidden. Refrigerators will not be used jointly for foods
and radioactive materials.
- One or more trial runs beforehand with non-radioactive materials are recommended
for new procedures and new personnel to test effectiveness of procedures
and equipment.
- Do not work with radioactive materials if there is a break in the skin
below the wrist.
- Always use gloves when handling more than a few hundred counts per minute.
Wear protective clothing (lab coats, masks, shoe covers) as needed.
- Table and bench tops should be of a non-porous, chemical resistant material.
Working surfaces shall be covered with absorbent paper regardless of the
type of surface.
- When work is completed each person will clean up his own work area and
arrange for disposal or proper storage of all radioactive materials and
equipment.
University of Illinois U.S. Nuclear Regulatory Commission http://www.nrc.gov
