Assessing dose of the representative person forthe purpose of radiation protection of the public

The Commission intended that its revised recommendations should be based on a
simple, but widely applicable, system of protection that would clarify its objectives and provide
a basis for the more formal systems needed by operating managers and regulators. The
recommendations would establish quantified constraints, or limits, on individual dose from
specified sources. These dose constraints apply to actual or representative people who
encounter occupational, medical, and public exposures. This report updates the previous
guidance for estimating dose to the public. Dose to the public cannot be measured directly
and, in some cases, it cannot be measured at all. Therefore, for the purpose of protection of the
public, it is necessary to characterise an individual, either hypothetical or specific, whose dose
can be used for determining compliance with the relevant dose constraint. This individual is
defined as the 'representative person'. The Commission's goal of protection of the public is
achieved if the relevant dose constraint for this individual for a single source is met and
radiological protection is optimised.
This report explains the process of estimating annual dose and recognises that a number of
different methods are available for this purpose. These methods range from deterministic
calculations to more complex probabilistic techniques. In addition, a mixture of these techniques
may be applied. In selecting characteristics of the representative person, three important
concepts should be borne in mind: reasonableness, sustainability, and homogeneity. Each
concept is explained and examples are provided to illustrate their roles. Doses to the public are
prospective (may occur in the future) or retrospective (occurred in the past). Prospective doses
are for hypothetical individuals who may or may not exist in the future, while retrospective
doses are generally calculated for specific individuals.
The Commission recognises that the level of detail afforded by its provision of dose coefficients
for six age categories is not necessary in making prospective assessments of dose, given
the inherent uncertainties usually associated with estimating dose to the public and with
identification of the representative person. It now recommends the use of three age categories
for estimating annual dose to the representative person for prospective assessments. These
categories are 0-5 years (infant), 6-15 years (child), and 16-70 years (adult). For practical
implementation of this recommendation, dose coefficients and habit data for a 1-year-old
infant, a 10-year-old child, and an adult should be used to represent the three age categories.
In a probabilistic assessment of dose, whether from a planned facility or an existing situation,
the Commission recommends that the representative person should be defined such that
the probability is less than about 5% that a person drawn at random from the population will
receive a greater dose. If such an assessment indicates that a few tens of people or more could
receive doses above the relevant constraint, the characteristics of these people need to be
explored. If, following further analysis, it is shown that doses to a few tens of people are indeed
likely to exceed the relevant dose constraint, actions to modify the exposure should be considered.
The Commission recognises the role that stakeholders can play in identifying characteristics
of the representative person. Involvement of stakeholders can significantly improve the
quality, understanding, and acceptability of the characteristics of the representative person
and the resulting estimated dose.


The optimisation of radiological protection: Broadening the process

The principle of optimisation of radiation protection is defined by the Commission
as the source-related process to keep the magnitude of individual doses, the number of people
exposed, and the likelihood of potential exposure as low as reasonably achievable below the
appropriate dose constraints, with economic and social factors being taken into account.
According to the revised recommendations of ICRP, this process of optimisation below
constraint should be applied whatever the exposure situation; i.e. planned, emergency, and
existing.
The previous recommendations for the practical implementation of the optimisation process
are still valid. It must be implemented through an ongoing, cyclical process that involves the
evaluation of the exposure situation to identify the need for action, the identification of the
possible protective options to keep the exposure as low as reasonably achievable, the selection
of the best option under the prevailing circumstances, the implementation of the selected option
through an effective optimisation programme, and regular review of the exposure situation to
evaluate if the prevailing circumstances call for the implementation of corrective protective
actions. However, the way in which the optimisation process should be implemented is now
viewed more broadly to reflect the increasing role of individual equity, safety culture, and
stakeholder involvement in our modern societies.
This report is a consolidation and an evolution of the Commission's recommendations
concerning the optimisation principle. After some background information on the foundation
and evolution of the principle, this report describes the main characteristics of the process,
addresses the issue of exposure distribution in that process, and provides the basic requirements
for its application in operation and regulation. A description of decision-aiding techniques
commonly used for practical implementation of the optimisation process is provided in
Annex A.