The thermodynamic model and corresponding Gibbs free energy expression of molten core corium U-Zr-Fe-O system were built up

and thermodynamic data was also established. The thermodynamic properties of million kilowatt PWR core corium was calculated

and the calculated phase diagram

phase fraction and phase composition were presented. The results indicate that with heating up from 2000 ℃

the corium passes through solid-single liquid phases coexistence

solid-double liquid phases coexistence

double liquid phases coexistence

gas-double liquid phases coexistence

and single gas phases. In the range of 2 500～2 950 ℃

it was a typical liquid phase separation zone

and liquid phase 1# is mainly rich in Fe

U

and Zr containing a certain amount of UO

2

. Liquid phase 2# is mainly rich in UO

2

ZrO

2

U and Zr containing a very small amount of Fe.