In nuclear reactor safety assessment, proper estimation of coolant behavior on a postulated loss-of-coolant accident is required to ascertain fuel integrity. An analytical model to calculate fluid behavior such as transient liquid level and void distribution in the pressure vessel during blowdown is presented in this paper. The model verification by experimental data is also presented.
In the analytical model, conservation equations of mass and energy are solved considering gas-liquid slip velocity by finite difference method.
The test vessel was a cylinder, 364mm I.D. and 7, 015mm high. Pressurized water was discharged in liquid and/or steam phases through one of the three nozzles which were attached to the vessel. Two-phase level and void distribution as well as vessel pressure etc. were measured.
Discharge flow rate is approximated by Moody's correlation with a coefficient. When calculated with a pertinent discharge coefficient, both pressure and residual fluid mass agree well with the experimental data. Gas-liquid slip velocity is calculated by Wilson's empirical correlation. Calculated liquid level and void distribution agree well with the experimental data.