In the SARNET2 WP8.3 THAI Benchmark the capability of current accident codes to simulate the iodine transport and behaviour in sub-divided containments is assessed. In the THAI test Iod-11 and Iod-12 made available for the benchmark, the distribution of molecular iodine (I2) in the 5 compartments of the 60 m³ vessel under stratified and well mixed conditions was measured. The main processes addressed are the I2 transport with the atmospheric flows and the interaction of I2 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 made for Iod-11 and eight for Iod-12 by seven organiza-tions using four different codes: ASTEC-IODE (CIEMAT, GRS, TUS), COCOSYS-AIM (AREVA, FZ-Jülich, GRS), ECART (Pisa University) and MELCOR (Pisa University, VTT). Different nodalisations of the THAI vessel with 20 to 65 zones were applied. For Iod-11 most participants conducted two calculations, the first one on their own and the fi-nal one with knowledge of the other participants‘ calculations. The main improvements for the final analysis concerned the nodalisation and the modelling of heat transfer. For Iod-12 only one calculation was performed by each participant. For Iod-11 and iod-12 in general the analytical thermal hydraulic results are in a fairly good agreement with the measurements. Only the calculated local relative humidity de-viates significantly from the measured values in all calculations. The results in Iod-11 for the local I2 concentration in the gaseous phase are quite diverse. Three calculations show only minor deviations from measurement, whereas the others are substantially dif-ferent to the measured I2 concentrations. For Iod-12 no calculation delivers a satisfactory evolution of the I2 concentration in all five compartments of the vessel. There are three mediocre results, which are from the same user-code combinations standing out in the Iod-11 exercise. These partly severe discrepancies have various reasons which are dis-cussed in the paper.
SARNET2 WP8 Benchmark on THAI multi-compartment iodine tests – Results for test Iod-11
GONFIOTTI, BRUNO;PACI, SANDRO;
2012-01-01
Abstract
In the SARNET2 WP8.3 THAI Benchmark the capability of current accident codes to simulate the iodine transport and behaviour in sub-divided containments is assessed. In the THAI test Iod-11 and Iod-12 made available for the benchmark, the distribution of molecular iodine (I2) in the 5 compartments of the 60 m³ vessel under stratified and well mixed conditions was measured. The main processes addressed are the I2 transport with the atmospheric flows and the interaction of I2 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 made for Iod-11 and eight for Iod-12 by seven organiza-tions using four different codes: ASTEC-IODE (CIEMAT, GRS, TUS), COCOSYS-AIM (AREVA, FZ-Jülich, GRS), ECART (Pisa University) and MELCOR (Pisa University, VTT). Different nodalisations of the THAI vessel with 20 to 65 zones were applied. For Iod-11 most participants conducted two calculations, the first one on their own and the fi-nal one with knowledge of the other participants‘ calculations. The main improvements for the final analysis concerned the nodalisation and the modelling of heat transfer. For Iod-12 only one calculation was performed by each participant. For Iod-11 and iod-12 in general the analytical thermal hydraulic results are in a fairly good agreement with the measurements. Only the calculated local relative humidity de-viates significantly from the measured values in all calculations. The results in Iod-11 for the local I2 concentration in the gaseous phase are quite diverse. Three calculations show only minor deviations from measurement, whereas the others are substantially dif-ferent to the measured I2 concentrations. For Iod-12 no calculation delivers a satisfactory evolution of the I2 concentration in all five compartments of the vessel. There are three mediocre results, which are from the same user-code combinations standing out in the Iod-11 exercise. These partly severe discrepancies have various reasons which are dis-cussed in the paper.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
