Radionuclide dispersion calculation in environmental radiation monitoring system of the PAKS NPP

The new Environmental Radiation Monitoring System of the Paks NPP in Hungary consists of three radiation release measurement posts (placed into the two ventilation stacks of the four units and into the ventilation stack of the spent fuel intermediate storage building), 9 radiation monitoring stations and 11 gamma-radiation measurement posts placed more or less evenly around the plant. The basic goal of the Environmental Radiation Monitoring System is to provide complex and reliable information about the releases in all operating modes to facilitate the adequate estimation of the situation and to promote the decision making. Thanks to the astonishing development in the digital technology and to the state-of-the-art, up-to-date measurement techniques, a new level of confidence can be reached. Unpredictable radioactive leakage of the containment can be detected and the radiological situation of a relatively large area can be calculated and predicted. A very reliable system can be constructed withstanding earthquake and protected against single failure. Based on reliable and detailed measurement data, advanced simulation methodology and well-designed graphical user interface, an easy-to-use operator advisory system can be created to help the decision making in the very first and most difficult period of a nuclear accident. It is very important that the same system is used with the same features during the normal operation of the nuclear power plant, too; this means that the operators are able to get the necessary 'hands-on' training in order to be able to use the system during extreme stress and very unusual situations, too. Shaping the system in close cooperation with plant engineers and operators is indispensable in order to achieve the aforementioned goals. (authors)