Predicting atmospheric dispersion of radionuclides. A summary of the first report of a working group in the U.K

This paper describes the first report of a Working Group established to review recent developments in atmospheric dispersion modelling and to propose models for use in the U.K. The series of reports are intended to give practical guidance on the estimation of dispersion of radioactive releases to the atmosphere. The first report deals with the short and medium range dispersion, that is from about 100 m to several tens of kilometres from the source, and is based on a Gaussian plume model. In this paper the justification for this choice by the Working Group is given and the proposed schemes for categorising atmospheric conditions are presented together with values of the associated dispersion parameters. The methods by which the results for short timescale releases can be modified to allow for prolonged releases and to obtain annual average concentrations are discussed. Finally, the topics which have already been agreed to be considered by the Working Group in future reports are identified