CLT Controller described an event when the required separation standard was uncertain during the use of a non-standard RADAR system.

Narrative

North operation; CLT main RADAR went out and we were using Maiden RADAR for separation. From approximately 10 NM south and out; separation was 5 NM; rather than 3. I was initially told I needed 5 NM between aircraft on the same runway unless they had each other in sight (visual) and were told to follow each other visually. A few minutes later; I was told that they only needed to have the airport in sight to diminish the separation between successive aircraft to less than 5 NM. Then; I was told that was incorrect and I needed 5 NM unless they had each other in sight and were following each other visually. Downwind traffic was descending to 6;000' and as aircraft was turned to join final; also at 6;000'; separation may have decreased to less than 5 NM as they passed. The Arrival West Controller took most aircraft off the RNAV; which resulted in the aircraft drifting closer to the final. Recommendation; ensure that everyone is on the same page with the procedure. There has not been adequate training and/or guidance on what the requirements are when RADAR goes out; other than 5 miles. There should be conclusive; unambiguous direction given by the CIC/FLM when we go into a nonstandard configuration.