Before you can size a valve for that you will need to know the pressure upstream of the BFW pump, or at wherever the BFW valve discharges.
I can almost guarantee that there will be cavitation in this application, just because there is a high pressure drop. However, it's not like the BFW Recurc valve in a supercritical fossil plant, which would require many stages of pressure reduction.
For this kind of pressure drop, cavitation containment trim is adequate. I'd use a 1 1/2" Valtek Mark 1 with single-stage cav-control trim, flow over the seat. Cv=4 (calculated Cv required is 2.1) The Cav-Control trim is a cage with drilled holes, so the cavitation bubbles meet and cancel in the center of the outlet. Fisher, Masoneilan, Leslie, etc. all have similar trims.