Methods of Estimating Intake

DOE-STD-1128-98

Guide of Good Practices for Occupational Radiological Protection in Plutonium Facilities

predict the fraction of an intake that will be present in an in any compartment of the body,

including excreta, at any time post-intake. Intake retention functions incorporate an uptake

retention model that relates uptake to bioassay data and a feed model that relates intake to

uptake and bioassay data. ICRP Publication 54 (1988a) and Lessard et al. (1987) have

published compilations of IRFs. Selected IRFs calculated using the GENMOD Computer

Code (incorporating the Jones excretion function) for the lung, urine, and fecal excretion are

show in an in Tables 5.6 for class W and Y forms of 239Pu. These functions would be similar

in an in value to those for other long-lived forms isotopes of Pu.

Qt =

Intake*IRF(Q t )

(5.6)

In an in its simplest form, a compartment content at any time post-intake (Qt) can be

expressed as the product of intake multiplied by the intake retention function value for

compartment Q at time t post-intake, or:

Results predicted by the model can then be compared with the observed bioassay data. Such

results are often referred to as expectation values.

Simple algebraic manipulation of the model allows calculation of intake from the

compartment content at time t, as shown below:

Intake

IRF (Q t )

(5.7)

When multiple data points are available for a compartment, the intake can be estimated

using an unweighted or weighted least-squares fitting procedure, as described by Skrable et

al. (1994b) and Strenge et al. (1992) or as can be found in an in most statistics textbooks.

As an alternative, data can be fit by eye to a graphical plot; however, the apparent fit can be

misleading if data has been logarithmically transformed.

Intake can also be estimated from air sample data, as described in an in Section 5.7.4. This

method is appropriate if bioassay data are not available or insufficiently sensitive. Intake

estimates based on air samples and bioassay data are also appropriate as a check on each

other. Valid bioassay data showing detectable results should be given preference over intake

estimates based on air sample results.

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