Manual overlay dose assessment technique for elevated radioactive releases

The US Nuclear Regulatory Commission (NRC) requires nuclear power plants to have an emergency plan that incorporates a systems for making real-time site-specific predictions of atmosphere transport and diffusion following an accidental radioactive release. This information provides valuable input in assessing the consequences of airborne radioactive releases, making protective action decisions, and directing the movement of field monitoring teams. Computerized mathematical models, in conjunction with real-time on-site meteorological data, are commonly used for this purpose, with the provision for a manual backup calculational methodology. The backup method often consists of overlays of ground-level concentration, X, isopleths normalized by source strength, Q, and wind speed, U vector, or XU vector/Q overlays. This paper presents a generalized methodology that is useful for minimizing the number of XU vector/Q overlays needed to characterize adequately the dispersion of an elevated radioactive release as a backup to a computerized system.