[en] The refill phenomena occurring from 200 min to 217 min during the TMI-2 accident, was analyzed by using measurement data such as the RCS pressure and the pressurizer level. At 200 min the HPI began to inject water into the core, which resulted in a primary system depressurization due to steam condensation, and the pressurizer water drained into the vessel, increasing the core level. It is believed that the core was completely covered by water by about 207 min, when the pressurizer level decrease and the RCS depressurization stopped. Continued HPI injection resulted in increasing hot leg water levels, and the pressurizer level began to increase at about 210 min, when water reached the level of the surgeline entrance to the hot leg. A set of equations describing the refill phenomena, and accounting for compression of the noncondensible gases, have been derived from theoretical considerations, and solutions for water levels throughout the RCS have been obtained to predict the above described incidents during the refill period. 4 refs., 10 figs