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DOE-STD-1136-2004
Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities
following collection by the subject worker is an effective means of providing a small degree of chain-of
custody. At the more complex level would be strict accountability requiring signature of issue, certification
of collection, and signature of submittal.
Procedures describing details of the bioassay program should be documented. These procedures
should include a description of sample collection, analysis, calibration techniques, QC, biokinetic
modeling, and dose calculational methods used.
5.5.3 Fecal Sampling
Fecal analysis is most useful in the first few days after a known acute exposure, since a large fraction
of either an ingestion or inhalation deposition is excreted in feces. Chronic inhalation exposures to class W
or Y uranium can also be characterized by fecal analysis, since a large fraction of the material clears to the
GI tract and is eliminated in feces. Urinalysis is the only reliable method for determining inhalation
exposures to class D uranium and for monitoring the excretion of systemic uranium. It also provides
complementary information, which, when used with in vivo or fecal monitoring results, contributes to
greater accuracy in internal dose assessments. Because urinalysis is generally less disruptive to work
schedules than in vivo monitoring and more acceptable to workers than fecal monitoring, it occupies a
prominent place in most uranium bioassay programs.
Fecal analysis is often more likely to detect exposure to highly insoluble class Y material than
urinalysis. The ratio between the fecal excretion level per day and the urine excretion level per day is
greater than 7, as calculated for a 90-day sampling interval. All action levels are above the typically
attainable MDA for fecal analysis of 0.1 pCi per L (ANSI 1996). Thus, it is recommended that facilities
that have a significant class Y uranium exposure potential should have fecal analysis capabilities available
to them, unless they have urinalysis methods that have MDAs well below the 0.1 pCi per sample
(ANSI/HPS 1995).
A fecal sampling program must be designed to optimize worker cooperation, whether collecting
samples at home or in the workplace. Since the frequency of fecal voiding varies greatly from person to
person, the sample collection program must be adaptable. Flexibility in sample dates is important. It is
suggested that when a fecal sample is required, the worker be provided with a kit and instructed to collect
the sample, noting the date and time of voiding on the sample label. This practice can reduce the
likelihood of unsuccessful samples. If multiple samples are required (for example, to collect the total early
fecal clearance following an acute inhalation exposure), the worker may be given several kits and told to
collect the next several voidings, noting the date and time of each.
Since the total fecal voiding should be collected, thought must be given to the kit provided. Fecal
sampling kits can be obtained from medical supply companies or designed by the site. A typical kit might
include a large plastic zipper-closure bag to hold the sample, placed inside a 1- to 2-liter collection bucket
with a tight-fitting lid. The bucket and bag can be held in place under a toilet seat by a trapezoid-shaped
bracket with a hole through it sized to hold the bucket. After sample collection, the zipper bag is sealed, the
lid is snapped tight on the bucket, and the bucket placed in a cardboard box.
Following collection, the provisions for sample handling, control, analytical, and QC are similar to
those described above for urine samples. One particular concern for fecal analysis is the potential
difficulty of dissolving class Y uranium in the fecal matrix. While nitric acid dissolution may be
adequate, enhanced digestion using hydrofluoric acid may be preferred.
5-21


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