(A) model for evaluation of containment heat transfer coefficient

Abstract

The containment atmosphere, in the cases of loss of coolant accident or major steam line break, is pressurized by the release of high energy coolant or steam into the containment atmosphere, and this pressure rise imposes a potential threat to the structural integrity of the containment building which is the final barrier against the release of radioactive materials to the environments. The peak containment pressure is highly dependent on the heat transfer coefficient between the containment atmosphere and heat absorbing structures. The estimate of heat transfer coefficient in this study uses the well-known correlations. Nusselt heat transfer coefficient for pure vapors is calculated and then corrected for the influence of noncondensable air using the various correlations according to the laminar or turbulent condition. The numerical calculation using the proposed model is accomplished employing the data measured in Carolinas Virginia Tube Reactor containment test 3. The calculated values for condensing heat transfer coefficient are compared with Tagami and Uchida correlations which are widely used in containment analysis. The calculated heat transfer coefficients are incorporated into the CONTEMPT-LT code as time dependent input and then have predicted the containment atmosphere pressure and temperature transient for CVTR test 3.