Eliminating pressure head effects

A second useful feature of microgravity is that pressure head effects are virtually eliminated. This is important in phase change studies where small gradients in pressure cause significant changes in the behavior of the phases. 

The tall riser and the reduced pressure losses in the reactor coolant system yield a large natural circulation ratio. This provides an effective circulation of coolant in the reactor coolant system to remove decay heat from the core. Finally, the tall riser provides sufficient space to accommodate internal CRDMs. Not only this allows eliminating the potential for a rod control cluster assembly (RCCA) ejection, but it also allows eliminating the CRDMs penetrations through the vessel upper head. Thus, the operational concerns associated with... 

In small-diameter columns, D/Ha is usually so small that the effect of cross flow is negligible, but in large columns it may become so great that the kinetic head equivalent to Vcf may be significant in terms of liquid head. Under these conditions, the pressure in the vapor space is not constant across the cross section, and its variation is such that it forces an increase in the hydraulic gradient. In order to make Hs as large as possible, any beams or projection on the bottom of a plate should be positioned to aid the vapor cross flow. Good vapor distribution on the plate will eliminate the effect of vapor cross flow. 

---