Determining the source term for emission of hazardous material from the faces of a building

Data from environmental monitoring stations are not always able to provide sufficient information on the emission of hazardous material resulting from an accidental release. A case study is presented for a nuclear research reactor with the combined use of experimental and numerical methods to determine the accidental source term of emission based on detectors located within few tens of meters from the reactor building. Wind tunnel experiments were carried out focusing on elaborating a method for determining the distribution of radioactive material in the vicinity of the Budapest Research Reactor (at the Atomic Energy Research Institute) should there be an accidental release. The aim of this work is to determine the concentration distribution around the building and the gamma dose measured by the detectors of the monitoring system for a unit’s accidental release through the faces (e.g. broken windows) of the reactor hall. The results provided by the wind tunnel experiments are used as input data for numerical calculation. The paper presents the principle of the method used in the wind tunnel experiments to determine the 3D concentration field, the basics of numerical calculation, as well as the measured and calculated results.