Evaluation of state-of-the-art two-velocity two-phase flow models and their applicability to nuclear reactor transient analysis, Volumes 1, 2, and 3. Final report

The state-of-the-art of two-velocity two-phase flow models is reviewed and evaluated in relationship to the present equilibrium, homogeneous flow models used to analyze the thermal-hydraulic response of nuclear steam supply systems to hypothetical transient incidents. The two-velocity models were compared against a set of criteria that are considered necessary to be satisfied in order to ascertain a more complete understanding of the actual, not conservative, thermal-hydraulic response of nuclear steam supply system to transient incidents. The review and evaluation of the two-velocity model considered (1) the approach used in formulating the differential field balance equations; (2) the adequacy of the constitutive models required to establish a closed system of equations; (3) the applicability of the finite difference numerical integration techniques selected; and (4) comparisons between model predictions and experimental data. Areas in which further model development is required are presented