Statistical studies on the limitation of short-time releases from nuclear facilities

The annual release quantities subject to licence can be determined for each nuclide from the release height, the site specific diffusion statistics of the diffusion category, wind velocity, wind direction and precipitation and from the dose limits of the national radiation protection regulations, if the releases of radioactive substances with the waste air take place at a constant release rate. The more or less constant release rates resulting from normal operation are generally superposed by increased short-time effluents. The ''General calculation principles'' of the Federal Republic of Germany specify the conditions under which such increased release rates may be treated by the long-time diffusion factors calculated for constant emissions. In this connection both the daily and the hourly release amounts are restricted. The present study was undertaken to find if this approach is conservative and the limitation of the daily release quantities for the different nuclide groups and exposure pathways would be sufficient to comply with the dose limits. The long-time dispersion factors for the different exposure pathways computed on the basis of the diffusion statistics are compared with ''quasi long-time dispersion factors'' that are calculated by superposition of sets of e.g. a hundred short-time diffusion situations. (H.K.)