The objective is to protect future generations to at least the same level as current generations. Compliance with that objective is measured using a single dose constraint value of 0.3 mSv/a (or an equivalent risk constraint of 2 × 10~5/a). Nevertheless, the interpretation of the calculated doses that are compared with this constraint changes with time. These doses are considered to be measures of health detriment for the first few hundred years, but only indicators of repository performance at longer timescales. Two other means of recognising this change in interpretation are suggested: (a) a cutoff of 1 000 to 10 000 years may be used for quantitative forecasts; and/or (b) qualitative judgements may be introduced at longer timescales. ICRP-81 also recognises the usefulness of alternative or supplementary criteria such as Best Available Technology (not entailing excessive cost), particularly at long timescales where direct quantitative measures of detriment are unavailable. As in ICRP-81, a single criterion is recommended regardless of timescale. However, it is recognised that at long timescales such a criterion is no longer a reasonable basis for decision making. As above, two means of dealing with long timescales are suggested, although these are not the same as the two methods proposed in ICRP-81: (a) use of the criteria as targets rather than as hard limits (exceeding the criterion need not result in rejection); and (b) possible replacement of the initial criterion with a different one, namely comparison with natural background levels.
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