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Dose projection is a tool for decision making in the case of a nuclear emergency situation. In this work the dose projection software developed for the Krško NPP located in Slovenia is described. This software can be used for a quick emergency evaluation in the case of a hypothetical pressurised water reactor accident, and for emergency exercises. The software was developed to estimate reactor core damage, the status of fission product barriers, potential releases, atmospheric dispersion and finally the dose calculation. The intention was to use all the available automatic on-line measurements of the radiological monitors in the NPP, meteorological monitors in the surroundings and a modern atmospheric dispersion model capable of accurate calculations in the complex orography which is characteristic of the plant location. It is also important that the software is written in a user-friendly way, automated as highly as possible and executed on a widely used Windows platform for PCs. Details are given in the paragraphs Measurements and software modules and Air pollution dispersion calculation module. The program should provide a dose projection at an early stage of the accident (first hours) for distances of a few kilometres from the NPP. The results are available for a 25 km by 25 km area that includes the Krško basin and some nearby hills and valleys. The results should support the decision of the emergency team in the NPP about evacuation or sheltering in the environment in the early phase of the accident. In the past the software used only a simple Gaussian air pollution dispersion model. Recently it was replaced with a numerical Lagrangean model called 'Spray'. Since the software was intended to be used for severe accident scenarios, it was also expected that the on-line meteorological and radiological parameters would not be completely available at all possible stages. For the case of missing radiological data, alternative possibilities were... [ABSTRACT FROM AUTHOR]

The accidents in Chernobyl and Fukushima remind us that nuclear power plants should continuously invest resources in improving safety and in risk management. This paper presents the methodology for developing a measuring and modelling system with a high degree of automation, which enables predicting the effects of the spreading of radionuclides from the nuclear power plant to the atmosphere. The end result is the calculated population doses in the event of an accidental release, which is an essential piece of information needed by first responders to take proper action. The key challenge addressed by this methodology is how to build a system so that its operation is maximally automated, ongoing and in real time. Moreover, in a way that "fresh", normalized results for the hypothetically most probable types of emissions are always available to operators. The principle that normalized, fresh results are always automatically available to operators is the only real assurance that they will almost surely be available in the event of an accident and panic. This way, we can avoid performing complex model calculations at the operator's request when the accident is already taking place. The methodology divides the building of the system into key modules, which are substantiated and described. The theoretical section is followed by a description of implementation on the example of the Measuring and Modelling System at the Krško Nuclear Power Plant (in Slovenia). The system has been tested in regular nuclear emergency exercises and rated excellent by IAEA inspections; it has been operating automatically, continuously and in real time for many years. The availability of automatic results is counted for the last two years. Measurements and diagnostic modelling results were available for more than 96% and forecasts were available in more than 91% of all half-hour intervals., (Copyright © 2019 Elsevier B.V. All rights reserved.)