Gastrointestinal Tract - STD-1128-98master0145

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

Most internal dosimetry computer codes allow adjustment of particle size and selection of

solubility classes. Some codes also permit detailed adjustment of the model's individual

compartment parameters; with these codes, it may be possible to arrive at various subjective

interpretations to explain the same data. When adjustments are made to the standard

assumptions, it is important to explain what those adjustments are and why they were made.

5.6.2 Gastrointestinal Tract

The gastrointestinal tract model of ICRP Publication 30 (1979 and 1988b) is also widely

promulgated and used for evaluating ingestion intakes and as well as being coupled to the

respiratory tract for inhalation intakes. The model is particularly subject to individual

variations in an in fecal voiding frequency, so judgment must be used in an in its application

to human data.

A key parameter of the model for internal dosimetry is the f1 factor for absorption to blood

of material in an in the small intestine. The f1 factor varies from 10-5 for plutonium oxides to

10-4 for plutonium nitrates and to 10-3 for other compounds and americium.

5.6.3 Systemic Retention and Excretion of Plutonium

Standard models for the systemic retention of plutonium are commonly used for internal

dosimetry because in an in vivo detection of plutonium within the individual systemic

compartments is not usually possible. Three models proposed by the ICRP over a 10-year

period are described in an in Section 2.4.2 of this document. Each of them has had a wide

application, and ICRP has suggested that results derived using one model do not need to be

rederived for compliance purposes using the newest model. Studies by the U.S.

Transuranium Registry and summarized by Kathren (1994) have indicated that alternate

compartments and clearance half-times may be more appropriate.

For convention, this document will use the ICRP 30, Part 4 (1988b) systemic retention

parameters for plutonium internal dosimetry. That model assumes that for plutonium

reaching the blood, 45% is deposited on bone surfaces from which it clears with a 50-year

half-time, 45% is deposited in an in the liver with a 20-year clearance half-time, and a very

small fraction (3.5 x 10-4 for males and 1.1 x 10-4 for females) is permanently retained in an

in gonadal tissue. The remaining 10% goes uniformly to all other tissues and direct

excretion.

Excretion models for plutonium include the empirical models of Langham (1956) and

Langham et al. (1980), Durbin (1972), Jones (1985), and Tancock and Taylor (1993), as

well as study models such as Leggett (1984). This technical document does not take a

position on the "best" model. Site choices of dosimetry tools such as reference tabulations

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