5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM
Relatively slow pressure transient as no sound wave propagation is considered and thermodynamic equilibrium is assumed in the saturated region.
Relatively low inlet enthalpy subcooling as liquid water properties are considered at the saturation point corresponding to the general pressure level. The pressure drop into the channel should be small relative to the general pressure level as the spatial variation of pressure is neglected in evaluating liquid and vapour properties.
All these limitations allow the calculation of every practical transient in BWR analysis with exclusion of blowdown. Transients with complete flow reversal are also excluded as no provision for coolant inlet from two directions is made. Local flow reversal in some subchannels is permitted in principle even if the correlations utilized are questionable in this event.