Das Projekt flexRISK wird aus Mitteln des Klima- und Energiefonds gefördert und im Rahmen des Programms "NEUE ENERGIEN 2020" durchgeführt. Weitere Informationen zu flexRISK und dem verantwortlichen Konsortium sind unter http://flexrisk.boku.ac.at/ zu finden.

flexRISK: Source Terms of Nuclear Installations in Europe

Within the investigation domain of the project flexRISK (Europe including the Mediterranean and the Caucasus regions), 258 civilian nuclear facilities were investigated: 234 nuclear power plants, 3 research reactors, 21 nuclear fuel cycle facilities (enrichment facilities, nuclear fuel production plants, reprocessing plants). Among the research reactors, only those with high thermal power and thus beyond-regional relevance were included. Facilities for purely military purpose were not included, however, some of the nuclear fuel-cycle facilities may be considered as (potentially) dual-use.

Figure 1: Nuclear installations considered (or not) in flexRISK (see also interactive map on http://flexrisk.boku.ac.at/intern/en/site_map.html) All data concerning nuclear installations are based on publicly available information: rated power, inventory, accident sequences, frequency of occurrence of accidents, releases for selected accidents etc., which are usually provided by the operators. In case of missing information the needed data was supplemented by data of similar installations. For each installation, a description can be found at http://flexrisk.boku.ac.at/en/site_list.html. As shown in Figure 2, the installations were divided into groups with similar characteristics. By far the biggest group (by numbers) are the pressurized water reactors (PWR), including also the Soviet VVER reactors (VVER old and new) and the EPR. Boiling water reactors (BWR), gas-cooled reactors (GCR) and Soviet RBMK are significantly rarer and are found in about the same numbers.

Das Projekt flexRISK wird aus Mitteln des Klima- und Energiefonds gefördert und im Rahmen des Programms "NEUE ENERGIEN 2020" durchgeführt. Weitere Informationen zu flexRISK und dem verantwortlichen Konsortium sind unter http://flexrisk.boku.ac.at/ zu finden.

Figure 2: Shares of the groups of nuclear installations taken into account by flexRISK All severe nuclear accidents having occurred so far took a course not taken into account in the safety considerations. This is, inter alia, due to the complexity of nuclear installations which makes a complete coverage of all accident situations impossible. For flexRISK, two potential severe accident sequences – thus not considered in the design basis accidents – were selected: A first scenario with a very large release of nuclear material – usually rather unlikely – and a second one with a larger probability und mostly smaller release. The restriction to two accident sequences, necessary for practical reasons, has as a consequence that the whole spectrum of possible accidents cannot be covered and therefore creates a certain blur. For the determination of the possible releases of radioactivity in the chosen accident scenarios the specific characteristics of each nuclear installation (e.g. retrofitting) were taken in consideration if known.

Even though the possibility of a severe nuclear accident is estimated to be small – 1 in 10 million operation years (that is comparable to winning the lottery !) – the damage caused by it is very large, as seen in the Chernobyl disaster: tens of thousands of people are still suffering from the effects of the disaster (illnesses, relocation, contaminated farmland, meadows and forests, …). Even in Austria, which is more than 1000 km away from the nuclear power plant, mushrooms and wild boars are contaminated with radioactive caesium 137. The frequency of occurrence of severe accidents assumed in flexRISK is derived from the calculation of the failure rates in all the imaginable event sequences. The figures provided by the operating companies come from probabilistic safety analysis (PSA), which, however, are not always based on comparable assumptions: Some only consider accidents caused by failure of nuclear power plant components, within which the aging of materials is difficult to include, others take accidents caused by external triggers into consideration (flooding, earthquakes, plane crash, …). Human error is especially difficult to quantify. The estimated frequencies of severe accidents are therefore afflicted with high uncertainties (factor of 10 and more). FlexRISK simulates the consequences of each accident for different meteorological conditions and, later on, will also be weighted by accident probabilities. Vienna, 2011.04.19