Click here to make tpub.com your Home Page

Page Title: Methods of Estimating Intake
Back | Up | Next

Click here for thousands of PDF manuals

Google


Web
www.tpub.com

Home

   
Information Categories
.... Administration
Advancement
Aerographer
Automotive
Aviation
Construction
Diving
Draftsman
Engineering
Electronics
Food and Cooking
Logistics
Math
Medical
Music
Nuclear Fundamentals
Photography
Religion
   
   

 



DOE-STD-1136-2004
Guide of Good Practices for Occupational Radiological Protection in Uranium Facilities
deposited 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. Before DOE Order
5480.11, many 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 ICRP Publication 2 (ICRP 1959). Many archived
historical records may have used this approach. DOE Order 5480.11 (now superseded) required
calculation of dose equivalent. Now, 10 CFR 835 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. 1994;
Strenge et al. 1992; ICRP 1988b; King 1987). These methods each employ an idealized mathematical
model of the human body showing how materials are retained 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 the human body. These functions are used to predict the
fraction of an intake that will be present 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 (ICRP
1988b) and others (Lessard et al. 1987) contain compilations of IRFs.
In its simplest form, a compartment content at any time post-intake (Q t) can be expressed as the
product of intake multiplied by the intake retention function value for compartment Q at time t post-
intake, or:
Qt = Intake IRF(Qt)
(5.9)
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:
(5.10)
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 (Skrable et al. 1994) and
Strenge (Strenge et al. 1992) or as can be found 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 have been logarithmically
transformed.
5-35


Privacy Statement - Press Release - Copyright Information. - Contact Us

Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business