Q. Wu et al., EXPERIMENTAL SIMULATION OF CERIUM DISPERSION PHENOMENA IN DIRECT CONTAINMENT HEATING, Nuclear Engineering and Design, 164(1-3), 1996, pp. 237-255
In a direct containment heating (DCH) accident scenario, the degree of
cerium dispersion is one of the most significant factors responsible
for the reactor containment heating and pressurization. To study the m
echanisms of the cerium dispersion phenomenon, a DCH separate effect t
est facility of 1:10 linear scale for Zion PWR geometry is constructed
. Experiments are carried out with air-water and air-woods metal simul
ating steam and molten core materials. The physical process of cerium
dispersion is studied in derail through various instruments, as well a
s with flow visualization at several locations. The accident transient
begins with the liquid jet discharge at the bottom of the reactor pre
ssure vessel. Once the jet impinges on the cavity bottom floor, it imm
ediately spreads out and moves rapidly to the cavity exit as a film fl
ow. Part of the discharged liquid flows out of the cavity before gas b
lowdown, and the rest is subjected to the entrainment process due to t
he high speed gas stream. The liquid film and droplet flows from the r
eactor cavity will then experience subcompartment trapping and re-entr
ainment. Consequently, the dispersed liquid droplets that follow the g
as stream are transported into the containment atmosphere, resulting i
n containment heating and pressurization in the prototypic condition.
Comprehensive measurements are obtained in this study, including the l
iquid jet velocity, liquid film thickness and velocity transients in t
he test cavity, gas velocity and velocity profile in the cavity, dropl
et size distribution and entrainment rate, and the fraction of dispers
ed liquid in the containment building. These data are of great importa
nce for better understanding of the cerium dispersion mechanisms.