CVG CTLR EXPERIENCED OPERROR AT 3000 FT WHEN ACFT ON ILS APCH EXECUTED PROC TURN THAT CONFLICTED WITH SUCCEEDING TFC ON THE SAME APCH PROC.

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RELIEVED A FELLOW ATC SPECIALIST FROM THE SATELLITE RADAR POS WITH MODERATE TFC. INCLUDED IN THE BRIEFING WERE 2 ACFT ENRTE FROM I69 TO HAO FOR INST TRAINING. I WAS TOLD THE FIRST ACFT WAS ON HIS OWN NAV AND CLRED FOR THE GPS RWY 29 APCH AND THE SECOND ACFT WAS ON A VECTOR TO ESTABLISH ADDITIONAL SPACING BTWN THE TWO. I EXPECTED THE FIRST ACFT TO EXECUTE A STRAIGHT-IN APCH AND AFTER I HAD ESTABLISHED APPROX 10 NM BTWN THE TWO ACFT. I ISSUED A VECTOR TO JOIN THE LOC OF RWY 29 TO THE SECOND ACFT. THE FIRST ACFT; HOWEVER; DID NOT EXECUTE A STRAIGHT-IN APCH BUT EXECUTED A PROC TURN. THE ACFT PASSED WITHIN 1 NM OF EACH OTHER BEFORE I ISSUED A VECTOR TO THE SECOND ACFT. CONTRIBUTING FACTORS: 1) I HAD JUST TRANSITIONED FROM 3+ YRS OF WORKING DIFFERENT SHIFTS AND SLEEP HAS BEEN DIFFICULT. I WAS ON ABOUT THE THIRD DAY OF 4 OR LESS HR OF SLEEP. SINCE WE DID NOT INSTRUMENT TRAINING ON THE PREVIOUS SHIFT; I WAS VERY UNFAMILIAR OR 'RUSTY' WITH THE INST TRAINING PROCS. 3) THE STARS CONFLICT ALERT SOUNDED BUT I COULDN'T TELL WHICH TARGETS WERE INVOLVED DUE TO OVERLAP. 4) DUE TO THE CONSTANT FALSE ALARMS GENERATED BY THE STARS SYS; THE FACT THAT THE CONFLICT ALERT SOUNDED DID NOT GET MY IMMEDIATE ATTN.