Occupational Intakes of Radionuclides Part 1 - ICRP
Occupational Intakes of Radionuclides Part 1 - ICRP
Occupational Intakes of Radionuclides Part 1 - ICRP
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DRAFT REPORT FOR CONSULTATION<br />
masses M ( rT<br />
) are given in Publication 89 (<strong>ICRP</strong>, 2002a), which supersedes<br />
Publication 23 (<strong>ICRP</strong>, 1975).<br />
(235) For both sexes, the values <strong>of</strong> the specific absorbed fractions<br />
(<br />
rT<br />
rS<br />
, ER<br />
)<br />
(<br />
rT<br />
rS<br />
, ER<br />
) <br />
for alpha particles, electrons, photons and neutrons<br />
M ( rT<br />
)<br />
are taken from Publication 125 (<strong>ICRP</strong>, 2012). For most source and target<br />
combinations, the absorbed fractions for photons, electrons and neutrons are based on<br />
Monte Carlo radiation transport calculations performed using the voxel phantoms for<br />
the <strong>ICRP</strong> reference adult male and adult female described in Publication 110 (<strong>ICRP</strong>,<br />
2009). These voxel phantoms are constructed from tomographic images <strong>of</strong> real<br />
persons, with the height and organ masses adjusted to the values given in Publication<br />
89 (<strong>ICRP</strong>, 2002).<br />
(236) For α particles the absorbed fractions are taken to be 1 for rS = rT and 0 for rS<br />
≠ rT in most cases. Exceptions are combinations <strong>of</strong> source regions and target tissues in<br />
the respiratory and alimentary tracts and in the skeleton. In these cases some regions<br />
are small enough for alpha particles to escape.<br />
(237) In the human alimentary tract and the human respiratory tract, absorbed<br />
fractions for photons are derived using the reference voxel models. For electrons and<br />
α particles, absorbed fractions given for the alimentary tract in Publication 100 (<strong>ICRP</strong>,<br />
2006) have been updated with supplementary calculations in Publication 125 (<strong>ICRP</strong>,<br />
2012). The absorbed fractions for electrons and α particles in the respiratory tract<br />
given in Publication 66 (<strong>ICRP</strong>, 1994a) were adopted in Publication 125 (<strong>ICRP</strong>, 2012).<br />
(238) In the skeleton, biokinetic models consider the source regions to be:<br />
trabecular bone surfaces and volumes<br />
cortical bone surfaces (CBS) and volumes. In the new skeletal models, CBS<br />
can be<br />
o haversian canal surfaces within the cortical bone cortex surrounding all<br />
regions <strong>of</strong> trabecular spongiosa<br />
o haversian canal surfaces within the cortical bone <strong>of</strong> the long-bone<br />
shafts<br />
o surfaces separating medullary marrow cavities and cortical bone shafts<br />
<strong>of</strong> the long bones<br />
trabecular bone marrow, corresponding to all bone marrow within regions <strong>of</strong><br />
trabecular spongiosa – both active and inactive marrow<br />
cortical bone marrow, corresponding to all bone marrow within the medullary<br />
marrow shafts <strong>of</strong> the long bones, as well as the fluids within the Haversian<br />
canals <strong>of</strong> all regions <strong>of</strong> cortical bone. In the adult, the marrow <strong>of</strong> the long<br />
bone shafts is 100% inactive marrow.<br />
and the target tissues to be:<br />
50 µm endosteal region and<br />
active (red) marrow.<br />
99
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