Conference Proceedings Paper
Experimental and Computational Analysis of Steam Condensation in the Presence of Air and Helium
NURETH-14 - 2011 September 25-30
Matteo Bucci (CEA Saclay)
Walter Ambrosini (Università di Pisa)
Nicola Forgione (Università di Pisa)
Francesco Oriolo (University of Pisa)
Sandro Paci (University of Pisa)
Among the different phenomena expected to occur within nuclear reactor containments during a
postulated loss of coolant accident, condensation on containment walls plays a major role, since
it represents an important heat sink for evacuating the energy released by the discharge of the
primary water. Nevertheless, condensation strongly affects other relevant phenomena, like
containment atmosphere mixing, that influences the distribution of noncondensable gases
hypothetically delivered in severe accident conditions. In this scenario, the role of condensation
is not obvious, since it can locally aid the hydrogen produced by the oxidation of the core
claddings to concentrate and reach flammability limits, providing a dangerous effect instead of a
positive one. The understanding of condensation in the presence of air and hydrogen is therefore
a fundamental task for the safety analyses of reactor containments. This research has been
carried out with the aim to contribute to the understanding of these phenomena. A double
strategy has been adopted, including complementary experimental and computational activities.
Novel data have been made available by the CONAN facility, investigating the effects induced
by light noncondensable gases in experimental configurations that were scarcely investigated in
past studies. Computational fluid dynamics (CFD) condensation models have been developed
and validated. The suitability of helium as a substitute for hydrogen in experimental activities
has been investigated by theoretical and computational analyses allowing to establish simple
criteria for the scaling of condensation tests in the presence of a light noncondensable gas.
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