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Research Papers: Nuclear Power

ASTEC, COCOSYS, and LIRIC Interpretation of the Iodine Behavior in the Large-Scale THAI Test Iod-9

[+] Author and Article Information
G. Weber

 Gesellschaft für Anlagen-und Reaktorsicherheit (GRS) mbH Forschungsgelände, D-85748 Garching, Germanygunter.weber@grs.de

L. Bosland

DPAM, SEMIC, LETR-CEN, Institut de Radioprotection et de Sûreté Nucléaire, Cadarache, BP 3 13115 Saint Paul Lez Durance, France

F. Funke

 AREVA NP GmbH, Paul-Gossen-Strasse 100, D-91052 Erlangen, Germany

G. Glowa

 AECL Chalk River Laboratories, Chalk River, ON, K0J 1J0, Canada

T. Kanzleiter

 Becker Technologies GmbH, Kölner Strasse 6, D-65760 Eschborn, Germany

J. Eng. Gas Turbines Power 132(11), 112902 (Aug 16, 2010) (12 pages) doi:10.1115/1.4001295 History: Received September 09, 2009; Revised December 21, 2009; Published August 16, 2010; Online August 16, 2010

The large-scale iodine test Iod-9 of the German Thermal hydraulics, Hydrogen, Aerosols, Iodine (THAI) program was jointly interpreted by means of post-test analyses within the THAI Circle of the Severe Accident Research NETwork (SARNET)/Work Package 16. In this test, molecular iodine (I2) was injected into the vessel dome of the 60m3 THAI vessel to observe the evolution of its distribution between water, gas, and surfaces. The main processes addressed in Iod-9 are (a) the mass transfer of I2 between the gas and the two sumps, (b) the iodine transport in the main sump when it is stratified and then mixed, and (c) the I2 adsorption onto, and desorption from, the vessel walls in the presence and absence of wall condensation. The codes applied by the THAI Circle partners were the Accident Source Term Evaluation Code (ASTEC)-IODE (IRSN, Saint Paul Lez Durance, France), Containment Code System (COCOSYS)-Advanced Iodine Model (AIM) (GRS, Garching, Germany), and Library of Iodine Reactions in Containment (LIRIC; AECL, Chalk River, ON, Canada). ASTEC-IODE and the Advanced Iodine Model (AIM) are semi-empirical iodine models integrated in the lumped-parameter codes ASTEC and COCOSYS, respectively. With both codes multicompartment iodine calculations can be performed. LIRIC is a mechanistic iodine model for single stand-alone calculations. The simulation results are compared with each other and with the experimental measurements. Special issues that were encountered during this work were studied in more details: I2 diffusion in the sump water, I2 reaction with the steel of the vessel wall in gaseous and aqueous phases, and I2 mass transfer from the gas to the sump. Iodine transport and behavior in THAI test Iod-9 are fairly well simulated by ASTEC-IODE, COCOSYS-AIM, and LIRIC in post-test calculations. The measured iodine behavior is well understood and all measured data are found to be consistent. The very slow iodine transport within the stratified main sump was simulated with COCOSYS only, in a qualitative way. Consequently, this work highlighted the need to improve modeling of (a) the wet iodine adsorption and the washdown from the walls, (b) the I2 mass transfer between gas and sump, and (c) the I2/steel reaction in the gaseous and aqueous phases. In any case, the analysis of the large-scale iodine test Iod-9 has been an important validation step for the codes applied.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Sketch of the THAI test vessel with Iod-9 iodine measurement devices

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Figure 2

Main sump with sampling positions and recirculation loop

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Figure 3

Gaseous iodine in the vessel

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Figure 4

Iodine adsorbed on the steel coupon

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Figure 5

Iodine in the main sump

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Figure 6

Iodine in the elevated sump

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Figure 7

Nodalisation of the THAI vessel for the ASTEC-IODE calculation

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Figure 8

COCOSYS nodalisation of the THAI vessel in Iod-9 configuration

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Figure 9

Iodine in the condensate

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Figure 10

Iodine mass balance

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Figure 11

I2 transport by pure diffusion in the totally stagnant main sump

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Figure 12

Water phase MTC correlation at Iod-9 conditions

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