Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
dynamics of organ retention and excretion so that they are applicable to the
interpretation of bioassay data as well as the calculation of dose coefficients.
1.6 Dosimetry implemented in this report
(36) Dose calculations involve the use of nuclear decay data, anthropomorphic
phantoms that describe the human anatomy and codes that simulate radiation
transport and energy deposition in the body. The data provided in this report are
calculated using revised decay data (Publication 107, ICRP, 2008), the ICRP
reference computational phantoms of the adult male and female based on medical
imaging data (Publication 110, ICRP, 2009) and well-established Monte Carlo codes
(Kawrakow et al, 2009), (Pelowitz, 2008), Niita et al, 2010. .
(37) For all dose calculations, radionuclides are assumed to be uniformly
distributed throughout source regions, although these can be whole organs (e.g. liver)
or a thin layer within a tissue (e.g. bone surfaces). Similarly, target cells are assumed
to be uniformly distributed throughout target regions that vary in size from whole
organs to layers of cells. Doses from ‘cross-fire’ radiation between source and target
tissues are important for penetrating photon radiation. For ‘non-penetrating’ alpha and
beta particle radiations, energy will in most cases be largely deposited in the tissue in
which the radionuclide is deposited. Photon and electron transport is followed for
most source and target combinations. Additionally special considerations are taken
into account for alpha and beta emissions in a number of important cases. These
include:
Doses to target cells in the walls of the respiratory tract airways from
radionuclides in the airways (ICRP, 1994a).
Doses to target regions in the alimentary tract from radionuclides in the lumen
(ICRP, 2006).
Doses to cells adjacent to inner bone surfaces (50 μm layer; see below) and all
red marrow from radionuclides on bone surfaces and within bone mineral.
1.6.1 Nuclear Decay Data, Publication 107 (ICRP, 2008)
(38) A fundamental requirement for dose calculations is reliable information on
half-life, modes of decay, and the energies and yields of the various radiations emitted
by nuclides and their progeny (Eckerman et al, 1994; Endo et al 2003, 2004). The
calculations in this report use the nuclear decay data provided in Publication 107
(ICRP, 2008). This publication replaces Publication 38 (ICRP, 1983) and consists of
an explanatory text, with an accompanying CD-ROM, providing data on the radiation
emissions of 1252 radioisotopes of 97 elements. Radioisotopes of elements of atomic
number less than 101 were included in Publication 107 if their half-lives exceed one
minute or if they are the progeny of a selected radionuclide and if the basic nuclear
structure data enabled a meaningful analysis of their emissions. Presentation using
CD-ROM has enabled the complete listing of emitted radiations, and more details of
Auger cascades and spontaneous fission data. The data given include: energies and
intensities of emitted radiations; beta, neutron and Auger-CK spectra; spontaneous
fission radiations and alpha recoil; half-lives, branching decay and chains; and no cutoff
on the number of emissions.
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