Occupational Intakes of Radionuclides Part 1 - ICRP

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DRAFT REPORT FOR CONSULTATION
planned – that may be of no direct benefit to them but the exposure situation may be
of benefit to society. The exposure of members of the public as a result of the planned
operation of practices is a prime example of this type of situation. The second band,
from 1 mSv to 20 mSv, is of greatest relevance in the context of this report, applying
in circumstances where individuals receive direct benefits from an exposure situation.
Constraints and reference levels in this band will often be set in circumstances where
there is individual surveillance or dose monitoring or assessment, and where
individuals benefit from training or information. Examples are the constraints set for
occupational exposure in planned exposure situations, or the reference levels for some
protective actions in emergency exposure situations (ICRP, 2007). Exposure
situations involving abnormally high levels of natural background radiation, or stages
in post-accident rehabilitation may also be in this band. The third band, from 20 mSv
to 100 mSv, applies in unusual, and often extreme, situations where actions taken to
reduce exposures would be disruptive. Reference levels and, occasionally, constraints
could also be set in this range in circumstances where benefits from the exposure
situation are commensurately high. Action taken to reduce exposures in a radiological
emergency is the main example of this type of situation.
(56) The Commission considers that it will usually be appropriate for dose
constraints to be fixed by an operator at the operational level or by expert bodies or
regulatory authorities. The overall responsibility should be with those who are
responsible for worker exposure.
(57) As described in Publications 75 and 78 (ICRP, 1997a,b), investigation levels
are set to trigger assessment of the conditions giving rise to the exposure. They are
therefore used retrospectively. Investigation levels can be set for any operational
parameter related to monitoring of individuals or of the working environment.
Investigation levels set for individual radionuclides should take account of the
presence of other radionuclides in the working environment.
2.2 Control of Worker Doses
(58) In occupational exposure, doses are often received from both external and
internal radiation sources. For external exposure, individual monitoring is usually
performed by measuring the personal dose equivalent using personal dosemeters and
taking this measured value as an acceptable estimate of the value of effective dose.
For internal exposure, committed effective dose values are determined from
measurements of radionuclide activities in the body, in bioassay samples or in the
workplace.
(59) For practical purposes, the annual effective dose, E, can in most situations of
occupational exposure be estimated as:
E H p ( 10)
E(
50)
where HP(10) is the personal dose equivalent from external exposure, normally
defined by the dose equivalent at a depth of 10 mm in the body below the
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