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personnel should also take a wipe sample from the surface of wounds or skin wherever
hot spots are noted via RADIAC.
The level of radioactivity in urine and feces can also be used to estimate internal
contamination. Initial radioactivity in urine and feces should be quantified with a baseline
sample, followed by multiple postexposure urine and fecal samples. A thorough
evaluation of serial samples is the only sure method of confirming contamination and
quantifying body burden, which are key components of successful treatment.
Bioassay methods vary according to each nuclide. Published methods can be found in
health physics texts and standard guidance documents (e.g., NCRP Report No. 65). Table
6.7 summarizes the sampling regimens for some important radionuclides. Biodosimetric
approaches are useful for insoluble nuclides that are either ingested or inhaled, because
inhaled particles will be swallowed and passed through the GI tract into feces.
Tritium exposure can be measured with a single voided urine sample. For uranium, a
baseline 24-hour urine sample should be collected as soon as possible after the exposure.
This establishes the pre-existing excretion of uranium commonly distributed in soil. This
initial urine sample is then followed by another 24-hour sample to measure new
contamination and an additional 24-hour sample 7–10 days later. Insoluble plutonium
may not appear in the urine until 2–3 weeks after ingestion, so both urine and fecal
bioassays are needed to identify this radionuclide.
Radiation Detection, Personal Protective Equipment,
Personnel Monitoring, and Decontamination
Detection Using Radiation Survey Meters
Various instruments are available for detecting and measuring radiation, which cannot be
detected by human senses. These instruments (Figure 6.8) use the energy of the radiation
to create an electrical “pulse,” which can then be measured and used to determine
information about the radiation field. These various Radioactivity, Detection, Indication,
and Computation meters are generally referred to by the acronym RADIAC.
Radiation detectors can be configured in several different ways. Some have an internal
probe, while others have an external probe connected by a wire. The intended use of the
meter is the most important factor in determining what configuration to use. If the meter
will be used only for large area surveys, an internal probe works fine. If the meter will be
used to determine the dose rate from a point source or to detect contamination, then an
external probe will most likely be used.
Things to check before using a RADIAC:
• Check to see if the meter is in calibration. Most calibrations are good for 1 year,
but always refer to the sticker on the meter, which indicates when calibration is
due.
• Inspect for physical damage (broken meter face, frayed cables, etc.).
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