The GI Tract Biokinetic Model

DOE-HDBK-1184-2004

These parameters may then be converted to the sp, spt, and st in the dissolution

model (Figure 5-4).

5.1.4

The GI Tract Biokinetic Model

The GI tract biokinetic model, which has already been discussed to some extent in

Section 5.1.1, is essentially the same model used in ICRP 30. STC particles enter

the GI tract though the stomach via clearance from the lungs and oral ingestion.

The f1 is assumed to be 0.1 for Type M) STC particles and 0.01 for Type S STC

particles. The tritium released from STC particles is absorbed into the bloodstream

from the small intestines as HTO. Ingestion of HTO is treated as a direct injection

into the bloodstream, bypassing the GI tract. A fraction of the HTO excreted from

the body leaves via the feces. As mentioned before, this fraction is (0.1)/3 and it is

assumed to enter the GI tract through the upper large intestine.

Figure 5-5. GI Tract Biokinetic Model.

5.1.5

Dosimetric Models

Ultimately, we would like to calculate the equivalent dose6 to the organs and tissues

listed in the first column of Table 5-3. These doses are then weighted with the

ICRP 60 terminology that is similar to the ICRP 26 dose equivalent.