The radiological consequences of notional accidental releases of radioactivity from fast breeder reactors: sensitivity of the incidence of early effects to the duration

The radiological consequences of a wide range of notional accidental releases from a 1300 MW(e) LMFBR were assessed in a study published in 1977 (NRPB-R53). In that study representative values were in general adopted for each of the important parameters while recognising that in reality they could vary considerably. In this study the sensitivity of the predicted incidence of early effects to the release duration, in so far as it affects the crosswind spread of the activity, is investigated. Two situations are considered; a short release in which the crosswind distribution of the activity is assumed to be Gaussian and a more prolonged release (as modelled in the initial study) in which the crosswind distribution of activity is assumed uniform over a 300 sector. For the particular conditions and population distributions considered, the incidence of early effects is greater for the short compared with the more prolonged release. The size of the increase depends upon the radionuclide composition, the magnitude of the release, the distribution of the exposed population, and the prevailing meteorological conditions, but in general the increase is not large. This relatively limited sensitivity indicates that the results obtained in the initial study can be assumed, to a good approximation, to be applicable irrespective of the release duration. (author)