Dispersion factors

The SAFRAN includes procedure for evaluation of worker's exposure inside the facility due to accidental radionuclide releases to the air. This is performed on the basis of precalculated dispersion factors.

Dispersion factors are available for the exposure distances 1 m, 2 m and the distance, above which diffusion factor for the same room volume becomes constant. Physically it means that complete mixing conditions within the room are established and the dose to worker depends on the exposure time.

Dispersion factors are available for the exposure durations 1 min, 5 min, 10 min, 0.5 h and 1 h.

Room volumes considered vary from relatively small rooms (50 m3) to relatively large rooms (3000 m3). With increasing of the room volume, variation of diffusion factor for the same exposure distance and exposure duration decreases. Therefore for large volume rooms, the diffusion factors calculated for 3000 m3 room can be used as conservative extrapolation.

Dispersion factors are calculated conservatively assuming that there is no contaminated air extraction from the room.