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
Following collection, the sample handling, control, analytical, and QC provisions are
similar to those described above for urine samples. One particular concern for fecal
analysis is the potential difficulty of dissolving class Y plutonium in the fecal matrix.
While nitric acid dissolution may be adequate, enhanced digestion using hydrofluoric
acid may be preferred.
MODELING THE BEHAVIOR OF PLUTONIUM IN THE BODY
A key issue to plutonium dosimetry is the modeling of how the material behaves in the
body. Some of the standard models are described below, with additional discussion on the
biological behavior given in Section 2.4. It is important that an internal dosimetry program
establish and document the routine models and assumptions used for dosimetry. Computer
codes typically incorporate standard models but may allow the flexibility to alter
parameters. When altered on an individual-specific basis, the revised models need to be
addressed in the pertinent case evaluations or the technical basis.
5.6.1 Respiratory Tract
The respiratory tract model of ICRP Publication 30 (1979 and 1988b) is commonly
published and included in reference books (e.g., Cember, 1996; Shleien, 1983) and
internal dosimetry computer codes, hence it is not reproduced here.
Like all models, the ICRP respiratory tract model represents anticipated behavior.
Once an exposure has occurred and actual data become available, deviations from the
model in light of the data are appropriate.
In practice, the model has proved extremely valuable for calculating derived
investigation levels and estimating intakes from bioassay data, using standard D, W,
and Y classes of material. Model interpretation becomes more subjective when
extensive data become available. Carbaugh et al. (1991) and La Bone et al. (1992)
have provided excellent examples of two cases where the standard lung model
assumptions did not fit the data.