Thermo Scientific NITON XL3t 500 User Manual page 162

Radiation and General Safety
Radiation Protection Basics
Exposure to Radiation
3-2 NITON XL3 Analyzer User's Guide
Distance
The closer you are to a source of radiation, the more radiation strikes you.
Based on geometry alone, dose increases and decreases with an
inverse-squared relation to your distance from the source of radiation
(additional dose rate reduction comes from air attenuation). For example,
the radiation dose one foot from a source is nine times greater than the dose
three feet from the source. Remember to keep your hands and all body parts
away from the front end of the analyzer when the shutter is open to
minimize your exposure.
Shielding Shielding is any material that is placed between you and the radiation
source. The more material between you and the source, or the denser the
material, the less you will be exposed to that radiation. Supplied or optional
test stands are an additional source of shielding for analysis. A backscatter
shield accessory is also available and may be appropriate in some
applications.
Human dose to radiation is typically measured in rem, or in
one-thousandths of a rem, called millirem (mrem), 1 rem = 1000 mrem.
Another unit of dose is the Sievert (Sv), 1 Sv = 100 rem. The allowable limit
for occupational exposure in the U.S (and many countries internationally) is
5,000 mrem/year (50 mSv/year) for deep (penetrating) dose and 50,000
mrem/year (500 mSv/year) for shallow (i.e., skin) dose or dose to
extremities. Deep, shallow, and extremity exposure from a properly used
NITON XL3t analyzer should be less than 200 mrem per year, (2.0 mSv per
year) even if the analyzer is used as much as 2,000 hours per year, with the
shutter open continuously. The only anticipated exceptions to the 200
mrem maximum annual dose are: 1) routine and frequent analysis of plastic
samples without use of a test stand, backscatter shield, or similar additional
protective measures, or 2) improper use where a part of the body is in the
primary beam path. NEVER OPERATE THE DEVICE WITH A PART
OF YOUR BODY IN THE PRIMARY BEAM PATH OR WITH THE
PRIMARY BEAM PATH DIRECTED AT ANYONE ELSE. Also,
consider the use of protective accessories such as a shielded test stand or
backscatter shield (or equivalent) when performing routine and/or frequent
analysis of any of the following:
• plastic (or similarly low density) samples,
• thin samples (such as foils, circuit boards, and wires), or
• samples that are smaller than the analysis window.
Shown in
received by the average member of the public. The radiation dose limits for
radiation workers in the US are also shown in
Table 3-1 below are the typical background radiation doses
Table 3-2.
Thermo Scientific