Advanced nuclear reactor concepts heavily rely on the availability and effi
ciency of passive cooling systems. This especially holds for advanced conta
inment designs with passive decay heat removal systems that function by nat
ural phenomena. Also, the development of catalyst modules for hydrogen miti
gation measures is based on natural basic principles leading to hydrogen re
duction and additional atmospheric mixing.
To prove the functionability and availability of passive systems and their
respective components, demonstration experiments at different scales are ma
ndatory. In addition, it is the general perception that many more improved
computational tools are needed for this purpose, where present lumped-param
eter analysis methods are insufficient to provide the necessary information
about local details and spatial distributions. Therefore, the next step in
the development of analytical/numerical models is the transition/extension
from lumped-parameter to multidimensional models and containment analysis
Also, recent posttest lumped-parameter analyses of the Heiss Dampf Reaktor
H-2, distribution experiment E11.2 with preexisting atmospheric stratificat
ion show a number of deficiencies compared with the data, indicating a need
for more detailed modeling.
The GOTHIC thermal-hydraulic containment code provides this required extens
ion of the lumped-parameter model by incorporating multidimensional submode
ls for selected nodes (subcompartments). Applications of both model types t
o simulate hydrogen dispersion experiments in the Battelle Model Containmen
t (BMC) demonstrate the limitations of the traditional approach and the imp
rovement achieved by the multidimensional simulation. The importance of the
rmal and hydrogen concentration stratifications, the interactions with stru
ctural heat conductors, and the requirements to set up a consistent model w
hen coupling lumped-parameter and multidimensional representations are disc
Several hydrogen-mixing experiments performed in the BMC more than a decade
ago were simulated with multidimensional GOTHIC models.
Three types of modeling concepts have been tested:
1. lumped-parameter model
2. each compartment modeled two-dimensionally with the intercompartment con
nections simulated as flow path junctions
3. full three-dimensional nodalization of the BMC, intercompartment connect
ions simulated as gaps.
The results of these GOTHIC calculations are compared with the experimental
data and demonstrate the improvements that can be achieved by performing m
ultidimensional containment simulations.