Ionizing radiation emits high energy
and overexposure can cause adverse
health effects. Its invisible and can
only be detected or monitored by using
special detection equipment.
Ionizing radiation carries enough energy to free
electrons from atoms or molecules. Three
common types you may come across in
labs are alpha, beta, and gamma radiation.
It's important to understand these types
of radiation, as penetration of the
skin by ionizing radiation can result in
the breakdown of DNA and long-term
health issues such as cancer. Alpha
radiation. Alpha radiation consists of
two protons and two electrons and has
the strongest ionization ability of the
three, but the weakest penetration. Paper
can be used as a barrier against alpha
radiation. Alpha rays will not penetrate
human skin, however the ingestion or
inhalation of alpha particles presents a
serious biohazard. Some common uses are
in smoke detectors and pacemakers.
Beta radiation. Beta radiation consists
of high-energy electrons or positrons
and has the median ionization and
penetration ability of the three.
Plexiglass or aluminum can be used as a
barrier against beta radiation.
Beta rays have the ability to penetrate human skin.
Some common uses are in medical imaging,
and leak detection in underground pipes.
Gamma radiation. Gamma radiation is
considered high energy electromagnetic
radiation and it has the lowest
ionization, but highest penetration of
the three. Lead shielding is the best
barrier against gamma radiation. Gamma
rays and higher energy radiation has the
ability to fully penetrate human skin
and tissue resulting in cellular damage.
Some common uses include the
sterilization of medical equipment, and
cancer treatment.
It's important to follow the principles
of radiation protection.
This will help avoid long-term health
effects associated with radiation
exposure such as: cancer, as well as acute
radiation poisoning. Symptoms of acute
radiation poisoning include: nausea,
vomiting, diarrhea, headache, fever,
seizures, and tremors. Always ensure you're
using appropriate personal protective
equipment while using radioactive
sources, including gloves.
You should also ensure you tape your lab
coat sleeves to protect against dangling
cuffs, and exposure of any skin on your
wrists and arms. Follow the time,
distance, shielding principle.
Time.
Always minimize the time of exposure.
Plan your actions in advance to
ensure you spend the minimum amount of
time exposed to a radiation source.
Distance. Maximize your distance from the
source.
The further away you are the less dose
of radiation you will receive. Shielding.
Always use the most shielding that
you can. When using shielding ensure the
appropriate materials are used. For beta
emitters, use plexiglass or aluminum. For
x-ray and gamma emitters, always use
lead shielding. For mixed emitters, use
plexiglass or aluminum as your first
layer of shielding, closest to the source.
Next, use a layer of lead as your
secondary layer of shielding. Areas that
often require more shielding are stock
solution storage, and waste collection
areas. As a result, make sure you have
enough shielding in these locations. You
can ensure this by checking with a
monitor to ensure the radiation level
outside the shielding is at par with
background levels.
Since ionizing radiation is invisible,
it should be monitored using a detector
while you work. An exception to this rule
is when working with tritium. Because it
has such low levels of radiation
emission it will not be detected by most
detectors. You can turn the detector
audio on, and leave the detector near the
workspace. Check your gloves occasionally,
taking care not to touch the detector
surface. Always ensure you're wearing a
radiation monitoring badge. These badges
will help determine your long-term
exposure and dose of radiation. Badges
should be stored away from sources of
radiation. Ensure you do not store your
radiation badge in direct sunlight as
this can register radioactive readings.
When monitoring for radiation at your
workstation you can use direct or
indirect monitoring methods.
Direct monitoring can
be achieved using a portable radiation
detection instrument. Start by verifying
that the instrument you have is
appropriate for the type of radiation
you'll be working with. Remember you
cannot use portable instruments for
tritium detection. When you require
gamma detection you must use solid
scintillation detectors, and not
gas-filled detectors. If you're unsure as
to which detection device is appropriate,
check with your supervisor or a colleague.
Once you've determined your detection
device, perform some routine checks to
ensure it will function properly. Ensure
the device has been calibrated within
the past 12 months.
Check the battery to ensure its
operational. Check high-voltage, if your
device has it. Perform an audio check. Check
that the detector window has not been
damaged. And finally, remove the detector
cover. You can also check the exterior of
the device for any obvious damage, such
as dents. Place the monitor as close as
possible to the surface you're testing
without touching it. Move it as slowly as
you can over the area, stopping whenever
you hear or see spikes in the number of
events being detected. Always confirm the
values at these spikes and write down
the measurements in the contamination
monitoring sheet. It's important that you
perform this monitoring procedure prior
to any work with a radioactive source, as
these readings will provide a baseline
in the event of any spills or accidents.
Another method of monitoring radioactive
contamination is by completing a wipe
test and using the liquid scintillation
counter. For this you will require filter
papers, a marker, vials, and scintillation
fluid. Ensure that your vials are the
appropriate size to fit into the liquid
scintillation counter. To start, take a
piece of filter paper and wipe an area of
about a 100 square centimeters or
approximately 4 by 4 inches. Place the
paper into the vial and label the vile
cap with a sample number. Place a clean
piece of filter paper into a separate
vial and label this as your negative
control. Fill each vial containing the
filter paper with scintillation fluid.
Place the samples in the liquid
scintillation counter. Ensure you make
note of which sample is in which spot.
You should also ensure you add a sample
with known activity. You can ask the
radiation safety officer for a standard
sample. This will be your positive
control. Run the samples using the
scintillation counter and analyze your
results. Once again, it's important to
perform this monitoring prior to
starting any work as these readings will
provide a baseline in the event of any
spills or accident
In the event of radiation spill, the key is
to ensure the protection of any persons
nearby, then secondarily to clean up the
spill. Start by ensuring you have the
appropriate personal protective
equipment, as well as a portable detector
that will detect the type of source you
have spilled. After each step of the
cleanup ensure you monitor the area, as
well as your gloves with the detector.
Apply the appropriate amount of
absorbent material to absorb the spill.
Pick up the material while wiping from the
outside-in towards the center of the
spill. If there's any broken glass ensure
you use tongs to pick it up. Use soap and
water, or the appropriate solvent - based
on what you've spilled - and clean the
area of the spill. Repeat these steps as
necessary, until the detector indicates
you have reached your background level. Keep
records of these levels and compare your
readings to your initial recordings to
ensure you've reached background levels. If
you cannot remove all contamination,
cover the contaminated area, and contact
the radiation safety officer for help
with fixed contamination. For a tritium
spill, you'll have to take wipe samples
of the area and check counts in the liquid
scintillation counter.
Once again if contamination still exists
after multiple cleanings, cover the area
and contact the radiation safety officer.
Ensure that you use appropriate labels
on your waste containers.