Nuclear Engineering and Design 273 (2014) 85–97 Contents lists available at ScienceDirect Nuclear Engineering and Design jou rn al hom ep age: www.elsevier.com/locate/nucengdes Computational analysis of modern HTGR fuel performance and fission product release during the HFR-EU1 irradiation experiment Karl Verfondern a,∗ , André Xhonneux a,2 , Heinz Nabielek b,1,3 , Hans-Josef Allelein a,c,4 a Research Center Jülich, Institute of Energy and Climate Research, 52425 Jülich, Germany b Research Center Jülich, Monschauerstrasse 61, 52355 Düren, Germany c RWTH Aachen, Chair for Reactor Safety and Reactor Technology, 52072 Aachen, Germany h i g h l i g h t s • HFR-EU1 irradiation test demonstrates high quality of HTGR spherical fuel elements. • Irradiation performance is in good agreement with German fuel performance modeling. • International benchmark exercise expected first particle to fail at ∼13–17% FIMA. • EOL silver release is predicted to be in the percentage range. • EOL cesium and strontium are expected to remain at a low level. a r t i c l e i n f o Article history: Received 19 September 2013 Received in revised form 17 January 2014 Accepted 22 January 2014 a b s t r a c t Various countries engaged in the development and fabrication of modern HTGR fuel have initiated activities of modeling the fuel and fission product release behavior with the aim of predicting the fuel performance under HTGR operating and accident conditions. Verification and validation studies are con- ducted by code-to-code benchmarking and code-to-experiment comparisons as part of international exercises. The methodology developed in Germany since the 1980s represents valuable and efficient tools to describe fission product release from spherical fuel elements and TRISO fuel performance, respectively, under given conditions. Continued application to new results of irradiation and accident simulation test- ing demonstrates the appropriateness of the models in terms of a conservative estimation of the source term as part of interactions with HTGR licensing authorities. Within the European irradiation testing program for HTGR fuel and as part of the former EU RAPHAEL project, the HFR-EU1 irradiation experi- ment explores the potential for high performance of the presently existing German and newly produced Chinese fuel spheres under defined conditions up to high burnups. The fuel irradiation was completed in 2010. Test samples are prepared for further postirradiation examinations (PIE) including heatup simula- tion testing in the KÜFA-II furnace at the JRC-ITU, Karlsruhe, to be conducted within the on-going ARCHER Project of the European Commission. The paper will describe the application of the German computer models to the HFR-EU1 irradiation test and compare within the preliminary experimental results as well as with previously conducted, true predictive calculations. Furthermore, results will be compared with the German code development STACY that extends the earlier codes toward new features. © 2014 Elsevier B.V. All rights reserved. Abbreviations: AVR, Arbeitsgemeinschaft Versuchs-Reaktor, high temperature reactor at Jülich, Germany; CRP, Coordinated Research Project directed by the IAEA; EOL, end-of-life; EU, European Union; HFR, High Flux Reactor at Petten, the Netherlands; HTGR, high temperature gas-cooled reactor; IAEA, International Atomic Energy Agency; ITU, Institute for Transuraniums at Karlsruhe; JRC, Joint Research Center of the European Commission; KÜFA, Kühlfinger-Apparatur, cooling finger furnace; PIE, postirradiation examination; TC, thermocouple; TRISO, tri-isotropic coating around a fuel kernel, composed of a sequence of layers of buffer, inner pyrocarbon, silicon carbide, and outer pyrocarbon. ∗ Corresponding author. Tel.: +49 2461 613438; fax: +49 2461 613010. E-mail addresses: k.verfondern@fz-juelich.de (K. Verfondern), xhonneux@lrst.rwth-aachen.de (A. Xhonneux), heinznabielek@me.com (H. Nabielek), h.j.allelein@fz-juelich.de, allelein@lrst.rwth-aachen.de (H.-J. Allelein). 1 Retired. 2 Tel.: +49 2461 619709. 3 .Tel.: +49 2421 62421. 4 .Tel.: +49 2461 613065/241 8095440. http://dx.doi.org/10.1016/j.nucengdes.2014.01.026 0029-5493/© 2014 Elsevier B.V. All rights reserved.