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This being said, prudence is the watchword concerning this definition and its general meaning.
This emerges in considering the incorporated activities to be taken into account. If one assumes that
these activities result from the incorporation of the fuel radionuclides by a single individual (which is
obviously unrealistic), this leads to doses with a deterministic effect to which the Sv unit does not apply
as we have seen. Thus the radiotoxic inventory of the fuel must be understood as an expression of the
collective dose [162] that would be received by numerous individuals if they incorporated the activity of
the fuel at rates which do not trigger deterministic effects. In this case the Sv unit can be used. Each
expression for radiotoxic inventory corresponds to a specific need.
Expressed in Sv/t or in Sv/TWhe, it is an operating and management tool for the production of
the waste, and, expressed in Sv/year, it is a management tool for a waste disposal project.
4.1.4 Assessment of the radiological risk
Evaluating the Radiological Risk, RR, requires associating the values of P i and of the doses D i
or E i whenever possible. This is where matters become complicated, particularly for events in the distant
future.
In relation to the back-end of the cycle, many factors must be considered:
• the periods of time, because the activities which can cause exposure are or will be spread
over long periods between the start of interim storage of the spent fuels and the disposal of
the wastes;
• the strategy, which may be non-reprocessing or some form of processing for the spent
fuels;
• the scenarios, normal and accidental, are based either on a sequence of natural events, or
are influenced by man and dependent on the installation. Each of these scenarios is itself
dependent on two types of parameters: physicochemical and sociological.
The evaluation of RR also depends on:
• the methodology used: deterministic with analysis of sensitivity to parameters, or
probabilistic;
• the modelling (radionuclide transfers to the biosphere and calculation of impact on man);
• the quality of the “tools” and the data.
Once the RR has been evaluated, decisions must be taken.
4.1.5 Decision framework
Decisions are taken on the basis of the Safety Analysis. This consists of:
• comparing the RR values with a number of considerations including:
– safety objectives: environment, present and future human health;
– ethical considerations: principle of fairness, principle of precaution based on beliefs in
the invariability of the characteristics of man, of society, and of the advancement of
knowledge;
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