SOURCE-TERM EVALUATIONS UNDER COMPLEX CONDITIONS IN REAL-TIME AND THEIR VALIDATION

Source term evaluations in emergency situations are very important for the precise assessment of the actual and probable future radiation ex posure of the people at risk. To this end relatively simple dispersion models (like the gaussian puff trajectory model) have to be used to o btain results in real-time with the computer technology at present ava ilable. In particular, applied to sites on complex terrain such a mode l needs a rigorous validation which takes into account the most import ant influences limiting, or at least disturbing, its reliability, as t here are aerodynamic effects due to the orography (hills, river valley s, etc.), urban areas, and sea-land interfaces, for instance. This, in turn, allows an enhancement of the quality of the dispersion model an d thus the accuracy of its results. In connection with the installatio n of a warning and emergency guidance system on some French coastal si tes a procedure has been developed to validate the dispersion model us ed with wind tunnel experiments. The validation strategy consists of t he following steps. (1) Measurements of concentration fields by wind t unnel experiments and subsequent evaluations of dose fields. (2) Calcu lations of concentration fields as similar as possible to the wind tun nel results with an advanced Lagrangian dispersion model. (3) Determin ation of hypothetical measurement values for doses and concentrations on certain measurement locations, on the basis of the calculations und er point (2). These serve as input for the dispersion model under cons ideration. (4) Assessment of the source term and dose fields with this dispersion model: the real-time feedback system CAIRE. (5) Comparison of the results of points (1), (2) and (4). For some applications the corresponding results will be presented.