[banerj1s]

Hi Sk,

Minimum recirculation line has nothing to do with priming though it does provides a faster FW pump startup. The priming is automatically obtained as the Deaerator is in the higher level which provides flooded suction. The minimum recirculation line is provided with ARC (automatic recirculation valve) so that the Feedwater Pump operate within stable region of the HQ curve. This is entirely for the safety of the pump.
Orifice is provided for minimum flow line for flow measurement. The flow signal shall be used to adjust the discharge control valve of the FW pump. There is a considerable pressure drop also. Normally the Orifice is at the downstream of the ARC.

Cheers

Sudipto