Several reasons it is considered a loss in cycle efficiency. first, when the unit is modeled in a cycle modeling computer program, it details the loss. Second, the mixing of cold liquid water with much hotter steam implies an increase in irreversability ( 2nd law) , which implies a loss of efficiency. Finally, it is often reasosned that the steam formed by the evaporation of the spray represents steam that bypasses the HP steam turbine.
"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick
The re-heat steam flow to the IP/LP turbines, it has already been through the HP.
So you can only recover the energy of the new steam in part of your turbine string.
The HP turbine produces power based on the HP steam flowing though it and the pressure ratio across the HP turbine. If the RH attemporator is downstream of the HP turbine, the steam produced by evaporating the spray water does not pass through the HP turbine.
"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick
