Title: Getting the details of fuel rod simulation in reactor safety analysis right: performance of the code coupling DYN3D-TRANSURANUS for RIA
Citation: Proceedings of the 45th Annual Meeting on Nuclear Technology
Publisher: German Nuclear Society
Publication Year: 2014
JRC N°: JRC89349
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC89349
Type: Articles in periodicals and books
Abstract: Over the last decades the importance of fuel-specific processes for safety analysis has grown, due to an increase of discharge burn-up for more efficient use of nuclear fuels. This results in a high burn-up structure (HBS) characterized by a decrease of the original grain size to ~0.1 - 0.2 μm, high concentration of pores with a diameter ~0.5 - 1 μm and depletion of fission gas from the matrix. It is known that the HBS can have an important effect on the fuel behavior during design basis accidents (DBA). For example, pellet cladding mechanical interaction (PCMI) can be observed under reactivity initiated accident (RIA) conditions, which can lead to fuel rod failure and in later stages to interaction between fuel and coolant. To analyze the behavior of high burn-up fuel in detail several experimental projects had begun, e.g. High Burnup Rim Project and the OECD/NEA Cabri Water Loop Project. Nevertheless, most of the reactor dynamics codes, thermal hydraulics system codes and sub-channel thermal hydraulics codes still include a simplified fuel behavior model. Thence licensing calculations concerning fuel rod performance are so far done in a conservative manner. However, today multi-physics code systems are more and more state-of-the-art thanks to hard- and software. For advanced safety analysis, two general trends can be observed in the field of fuel behavior modeling. On the one side, fuel performance codes are still being improved for a more accurate simulation of design basis accident (DBA) conditions. On the other side, the benefit and potential is being analyzed resulting from replacement of simplified fuel behavior models in neutronics, thermal hydraulics and CFD codes by a two-way coupling approach to a fuel performance code. Nevertheless, no real two-way coupling to a fuel performance code has so far been reported in the open literature for calculating a full core with detailed and well validated fuel behavior correlations. Thence in 2012 several German institutions wanted to couple their codes to the fuel performance code TRANSURANUS [16], which is used in EU by research organizations, safety authorities and industry. GRS has considered a coupling to its thermal hydraulics system code ATHLET, KIT presented a first external coupling approach for its sub-channel code KTF, and HZDR started a development for coupling TRANSURANUS to its reactor dynamics code DYN3D.
JRC Directorate:Nuclear Safety and Security

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