Nuclear Engineering and Design 265 (2013) 95–107 Contents lists available at ScienceDirect Nuclear Engineering and Design j ourna l h om epa ge: www.elsevier.com/locate/nucengdes Thermal-hydraulic–iodine chemistry coupling: Insights gained from the SARNET benchmark on the THAI experiments Iod-11 and Iod-12 G. Weber a,∗ , L.E. Herranz b , M. Bendiab c , J. Fontanet b , F. Funke c , B. Gonfiotti f , I. Ivanov d , S. Krajewski e , A. Manfredini f , S. Paci f , M. Pelzer a , T. Sevón g a GRS, Garching and Cologne, Germany b CIEMAT, Madrid, Spain c AREVA NP, Erlangen, Germany d TUS, Sofia, Bulgaria e FZ-Jülich, Jülich, Germany f Università di Pisa, Pisa, Italy g VTT, Espoo, Finland h i g h l i g h t s • The I 2 transport in two multi-compartment THAI tests was analyzed. • In a benchmark 4 different codes were applied by 7 organizations. • The I 2 concentrations were mostly overestimated, up to a factor 100. • Inadequate iodine models and inaccurate thermal-hydraulic parameters were detected. • The user effect on the quality of the iodine results was large. a r t i c l e i n f o Article history: Received 9 January 2013 Received in revised form 16 July 2013 Accepted 25 July 2013 a b s t r a c t In the SARNET2 WP8.3 THAI Benchmark the capability of current accident codes to simulate the iodine transport and behavior in sub-divided containments has been assessed. In THAI test Iod-11 and Iod-12, made available for the benchmark, the distribution of molecular iodine (I 2 ) in the five compartments of the 60 m 3 vessel under stratified and well mixed conditions was measured. The main processes addressed are the I 2 transport with the atmospheric flows and the interaction of I 2 with the steel surface. During test Iod-11 the surfaces in contact with the containment atmosphere were dry. In Iod-12, steam was released, which condensed on the walls. Nine post-test calculations were conducted for Iod-11 and eight for Iod-12 by seven organizations using four different codes: ASTEC-IODE (CIEMAT, GRS and TUS), COCOSYS-AIM (AREVA, FZ-Jülich and GRS), ECART (Pisa University) and MELCOR (Pisa University and VTT). Different nodalizations of the THAI vessel with 20–65 zones were applied. Generally, for both tests the analytical thermal-hydraulic results are in a fairly good agreement with the measurements. Only the calculated local relative humidity deviates significantly from the measured values in all calculations. The results in Iod-11 for the local I 2 concentration in the gaseous phase are quite diverse. Three calculations show only minor deviations from the measurement, whereas the others are substantially different from the measured I 2 concentrations. For Iod-12, no calculation delivers a satisfactory evolution of the I 2 concentration in all five compartments of the vessel. There are three mediocre results standing out in the Iod-11 exercise which are from the same user–code combinations. The discrepancies derive from various reasons which are discussed in the paper. In the benchmark a significant user effect was detected, i.e. results achieved with the same code differed considerably. This work highlights the need of a detailed iodine adsorption/desorption model and precise thermal- hydraulic modeling for an accurate simulation of I 2 transport in a sub-divided containment, as well as experienced users or straight forward user guidelines. © 2013 Elsevier B.V. All rights reserved. ∗ Corresponding author at: Gesellschaft für Anlagen- und Reaktorsicherheit (GRS)mbH, Germany. Tel.: +49 89 32004 506; fax: +49 89 32004 300. E-mail address: gunter.weber@grs.de (G. Weber). 0029-5493/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nucengdes.2013.07.012