The RELAP5 calculation results for a series of gravity-driven emergenc
y core-cooling (ECC) experiments with the parallel channel test loop (
PACTEL) facility are provided. The simulated accident was a small-brea
k loss-of-coolant accident with a break in one hot leg of the three lo
ops of the facility. The ECC flow was provided from a core makeup tank
(CMT) located at a higher elevation than the main part of the primary
system. The CMT was pressurized with pipings from the pressurizer and
a cold leg. The tests indicate that rapid condensation in the CMT inf
luences the ECC flow. The experimental results are numerically analyze
d using the RELAP5/MOD3.1 code. The calculations show good agreement w
ith the tests except in the modeling of rapid condensation.