Nei ho,
As far as i know, and thatīs what we have set at my unit (Canarias ACC), if radar fails the old plain "conventional" procedures are to be followed. Flight plan strips, calculations and everybody to the holding pattern at assigned altitudes/FLs. Same applies to Enroute sectors: old conventional procedures, VOR separations and distance/minutes.
Best regards.
PD.- Or more likely you can fall in your knees and start to pray...