Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
Subsequent reports in the series present radionuclide-specific information for the
design and planning of monitoring programmes and retrospective assessment of
occupational internal doses.
(9) The material presented in this report series is not intended for applications
beyond the scope of occupational radiation protection. An example of such an
application is the assessment of a case of substantial radionuclide intake, where organ
doses can approach or exceed the thresholds for tissue reactions, and where medical
treatment may require an individual-specific reconstruction of the magnitude of
absorbed doses and associated parameters characterising the exposure.
1.2 Protection quantities and dose coefficients in this report series
(10) The protection quantities defined by ICRP, equivalent dose and effective dose,
are fundamental to the application of ICRP recommendations. The concept of
effective dose provides a single quantity that may be used to characterise both internal
and external individual exposures in a manner that is independent of the individual’s
body-related parameters, such as sex, age (for adults), anatomy, physiology and race.
In order to achieve wide applicability, the protection quantities (effective dose and
equivalent dose) are defined using computational models with broad averaging of
physiological parameter values. Specifically, Publication 89 (ICRP 1975, 2002)
defines the key parameters of the Reference Individuals (the mass, geometry and
composition of human organs and tissues), while this report series provides relevant
parameters for the Reference Worker (ICRP 1994) together with an associated set of
ICRP reference biokinetic models.
(11) Effective dose is not an individual-specific dose quantity, but rather the dose
to a Reference Person under specified exposure conditions. In the general case, the
Reference Person can be either a Reference Worker (see Glossary) or a Reference
Member of the Public of a specified age.
(12) The protection quantities for internal exposure (committed effective dose and
committed equivalent dose) are derived using models and are not directly measurable.
For retrospective assessments of internal exposure, the dose can be assessed from
measurements of the amounts of radionuclides in the human body, their rates of
excretion or their concentrations in the ambient air. In contrast, the operational
quantities for exposure to external radiation fields are directly measurable.
(13) The dose coefficients and dose per unit content values presented in this report
series are given for a Reference Worker with an average breathing rate of 1.2 m 3 h -1
during an 8 h working day.. These data are provided for a range of physico-chemical
forms for each radionuclide and for a range of aerosol particle size distributions. Data
for ingestion and injection (i.e. direct entry to the blood) are provided to allow the
interpretation of bioassay data for cases of inadvertent ingestion (e.g. of material on
contaminated skin) or rapid absorption through intact or damaged skin (injection).
(14) While the generic definition of protection quantities remains unchanged in the
most recent recommendations (ICRP, 2007), there have been changes that affect
calculated values of dose per unit radiation exposure, including changes to radiation
and tissue weighting factors, adoption of reference computational phantoms (ICRP,
2009), and the development of the new generation of reference biokinetic models.
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