A burning issue: GRS carries out research into fire protection in nuclear power plants
Knowledge about the origin and propagation of fires is an important basis for evaluating the fire safety of a nuclear power plant. For this reason, GRS is currently conducting research in two international projects of the Committee on the Safety of Nuclear Installations (CSNI) on the subject of fire protection in nuclear installations: the PRISME project and the HEAF project.
The CSNI is an international body of the Nuclear Energy Agency (NEA) of the Organisation for Economic Cooperation and Development (OECD). It coordinates all NEA projects dealing with the safety of nuclear installations. At CSNI, GRS is one of the official representatives of Germany alongside the Federal Ministry of Economics and Energy (BMWi); the Vice Chair is one of GRS’s staff.
PRISME: Experiments on the propagation of fires and smoke
In the PRISME project, an international research team has been investigating the spread of fires and smoke in nuclear power plants since 2006. The abbreviation PRISME stands for the French Propagation d'un incendie pour des scénarios multi-locaux élémentaires - in English Fire propagation in scenarios of multi-room geometries.
At a facility of the French research institute Institut de Radioprotection et de Sûreté Nucléaire (IRSN) at Caderache, several series of realistic fire tests are being carried out for the PRISME projects. For this purpose, certain rooms of a nuclear power plant including their equipment and ventilation were reproduced to scale.
In the first phase of the project (PRISME 1), the propagation of heat, smoke and gases from room to room was investigated. The effects of ventilation conditions in rooms of a nuclear power plant were also taken into account. The aim of the investigations was, among other things, to investigate the thermal load acting on safety-relevant equipment.
Building on this, the researchers dealt in phase two of the project (PRISME 2) with the influence of measures to fight a fire (e.g. permanently installed spray water extinguishing systems). The spread of smoke and heat through an opening in the ceiling was also investigated.
The current phase of the project (PRISME 3) focuses on fires in electrical installations, such as switchgear cabinets and cables. Faults in this area are among the most frequent causes of fires in nuclear power plants.
GRS has been involved in PRISME since the first project phase. In PRISME 3, GRS is in charge of technical support and implementation on behalf of the Federal Environment Ministry and the Federal Ministry of Economics and Energy. One focus of GRS's work is the simulation of fire scenarios. The results of the experiments are calculated both in advance and afterwards, using the simulation codes. By comparing the calculation with the actual measurement, the reliability of a code can be demonstrated.
HEAF: Failure of the electronics in the switchgear cabinet as cause of fire
The international CSNI project HEAF investigates fires resulting from so-called High Energy Arcing Faults (HEAF). Arcing occurs when voltage differences between two electrically charged components are suddenly equalised. Arcing occurs, for example, when medium and high-voltage switches are opened and closed, which is why these switching operations must be carried out very quickly.
Arc faults are arcs that lead to damage or accidents. Since an arc can have a core temperature of around 10,000 degrees Celsius, there is a risk that the metal parts of the affected component (e.g. switchgear cabinet, transformer or cable) will evaporate explosively and possibly cause a fire.
For HEAF, a series of tests is being conducted on the high-energy failure of electrical components due to arc faults with possible subsequent fire. It is the US-American supervisory authority U.S. NRC that carries out the experiments, with the other project partners providing components or co-financing the experiments. In the first project phase, for example, Germany provided two high-voltage switchgears from a German nuclear power plant.
Currently, further tests with medium-voltage switchgear, which are to take place in 2019 and 2020, are being prepared within the framework of the next project phase. Germany provides eight switchgears of different voltage levels for these experiments.
GRS procured the switchgear cabinets and organized their dismantling at the nuclear power plant and the transport to America. Furthermore, in the second phase of HEAF, GRS will participate in the technical supervision of the tests and the in-depth evaluation of the test data on behalf of the Federal Environment Ministry. Despite the national phase-out of nuclear technology, the topic is interesting for Germany as the switchgear cabinets will be used for a longer period of time even after the shutdown of the plants, both in the post-operational phase and during dismantling. The results of the research project are incorporated into the evaluation and maintenance of and the further research into the safety of nuclear installations. In addition, the results can be used in many other industrial areas in which switchgear cabinets are used.
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