Methods of Estimating Intake - STD-1128-98master0152

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

conjunction with bioassay data to evaluate the intake, uptake, and retention of plutonium in an in the

organs and tissues of the body. Intake estimates can then be used to calculate committed effective

and organ dose equivalents. It is essential that good professional judgement be used in an in

evaluating potential intakes and assessing internal doses. Carbaugh (1994) has identified a number

of considerations for dose assessments.

Computer codes are commonly used for assessment of intakes, dose calculation, and bioassay or

body content projections. La Bone (1994a) has provided an overview of what should be considered

in an in selecting a computer code, as well as descriptions of a number of internal dosimetry codes

available in an in 1994. Internal dosimetry code users should understand how the code works and be

aware of its limitations. Computer codes merely provide the logical result of the input they are

given. Use of a particular computer code does not necessarily mean a dose estimate is correct.

As used in an in this section, the definition of "intake" is the total quantity of radioactive material

taken into the body. Not all material taken into the body is retained. For example, in an in an

inhalation intake, the ICRP Publication 30 respiratory tract model predicts that, for 1-m particles,

63% of the intake will be deposited in an in the respiratory tract; the other 37% is immediately

exhaled (ICRP, 1979). For a wound intake, material may be initially deposited at the wound site.

Once the material has been deposited, it can be taken up into systemic circulation either as an

instantaneous process (e.g., direct intravenous injection of a dissolved compound) or gradually (e.g.,

slow absorption from a wound site or the pulmonary region of the lung). Both the instantaneous and

slow absorption processes are often referred to as uptake to the systemic transfer compartment (i.e.,

blood). Once material has been absorbed by the blood, it can be translocated to the various systemic

organs and tissues.

An understanding of this terminology is important to review of historical cases. In an in the past

sites reported internal doses not as dose equivalent estimates but as an uptake (or projected uptake)

expressed as a percentage of a maximum permissible body burden (MPBB). The standard tabulated

values for MPBBs were those in an in ICRP Publication 2 (ICRP, 1959). Many archived historical

records may have used this approach. DOE Order 5480.11 (superseded), required calculation of

dose equivalent. Now, 10 CFR 835 (DOE, 1998a), has codified the calculation of intakes and

committed doses.

5.8.1

Methods of Estimating Intake

There are several published methods for estimating intake from bioassay data (Skrable et al.,

1994a; Strenge et al., 1992; ICRP, 1988b; King, 1987; Johnson and Carver, 1981). These

methods each employ an idealized mathematical model of the human body showing how

materials are retained in an in and excreted from the body over time following the intake.

An intake retention function (IRF) is a simplified mathematical description of the complex

biokinetics of a radioactive material in an in the human body. These functions are used to

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