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APPENDIX IV 73
T he D W L fo r a g iven fo o d s tu ff K is th e r e fo r e given by
DWW =
K
__ F aK______
J_ ) F, g. + ZaR
IL L ai gl Dl
2.3. DWL for the case of a mixture of radionuclides
In the case of a mixture of various radionuclides summations
similar to those mentioned under section 2.2 must be carried out
for each critical organ. It must be realized that if three or more
critical organs receive important fractions of their respective dose
limits, the irradiation must be regarded as 'whole body'.
If the mixture has a fraction of activity p. from nuclide j, the
following relation holds for each critical organ
where Wj is the DWL for the case of the isolated nuclide, as in
section 2.2. The above equations (one for each critical organ)
form a set from which the smallest DWLj values are selected.
2.4. 'Exposure model' and parameters employed
The 'exposure model' employed does not include the input or
the primary dispersion process. It is based on a compartment
common to all irradiation pathways (air in the case of stack releases
and water in the case of river releases).
Figure 3 describes the model for the case of atmospheric
releases. Depending on the particular radionuclide, the critical
organs may be: thyroid, haematopoietic tissue, lung, gastrointestinal
tract, gonads, or 'whole-body'. Also, the critical organs
can be those of 'standard' adults or of children, depending on the
radionuclide and the pathway involved. Figure 4 represents the
model for aqueous releases. Both'models were used in the 'timeindependent'
form, i.e . in the state of dynamic equilibrium. The
values obtained are also valid in the case of single releases, if
interpreted as time integrals and 'committed doses'.