Experimental and Computational Analysis of Steam Condensation in the Presence of Air and Helium
NURETH-14 - 2011 September 25-30

Presented at:
2011 September 25-30
Toronto, Canada
Session Title:
A1-2 Boiling and Condensation Fundamentals

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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