Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
Figure 20. Structure of the systemic biokinetic model for cobalt used here
(223) The systemic biokinetic models used in this report include explicit routes of
biological removal of systemic activity in urine and faeces. Additional excretion
pathways such as sweat are also depicted in the models for some elements.
(224) The biokinetic model adopted for the urinary bladder is described in
Publication 67 (ICRP, 1993b) and Publication 68 (ICRP, l994b). The number of voids
per day is taken to be six for workers. To represent the kinetics of the bladder in terms
of first-order processes, the rate of elimination from the bladder is taken to be 12 d -1 .
(225) Activity is assumed to be removed in faeces after transfer from systemic
compartments into specified segments of the alimentary tract representing elementspecific
endogenous secretion pathways. The rates of transfer of secreted material
through different segments of the alimentary tract are element-independent rates
specified in the HATM. Activity transferred from systemic compartments into the
contents of the small intestine or higher segments of the tract is assumed to be
reabsorbed in part to blood, with fractional absorption usually but not always assumed
to be the same as that for swallowed activity. Activity assigned to the contents of the
right colon or lower sections of the tract is not subject to reabsorption.
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