AN A319'S FUEL TRANSFER VALVE FAILED CREATING A FUEL IMBALANCE. AN EMER WAS DECLARED WITH A DIVERSION TO A NEARBY ARPT.

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DURING THE CRUISE SEGMENT WE RECEIVED AN ECAM ALERT SHOWING THAT THE FUEL XFER VALVE IN THE R WING TANK HAD MALFUNCTIONED. THE RESULT OF THIS ALERT WAS THAT 3000 LBS OF FUEL ABOARD THE ACFT WAS NOW UNUSABLE. I XFERRED THE FLYING DUTIES TO THE FO AND WE PROCESSED THROUGH THE ECAM AND QRH PROCS ASSOCIATED WITH THE MALFUNCTIONS. IT WAS QUICKLY DETERMINED THAT CONTINUATION TO DEST WAS NOT GOING TO BE POSSIBLE. WE NOTIFIED ATC THAT A DIVERSION WAS LIKELY IN THE NEXT FEW MINS. I CONTACTED THE DISPATCHER AND THROUGH A SERIES OF RADIO AND ACARS MESSAGES HE REQUESTED THAT WE DIVERT TO ZZZ BECAUSE ATC WOULD NOT ACCEPT US AT ZZZ1. BY THE TIME THAT SOME OF THIS CUMBERSOME COMS ENDED WE WERE 80 MI S OF ZZZ. I FELT THAT RETURNING TO ZZZ COULD POTENTIALLY MAKE OUR SITUATION QUITE CRITICAL I DECIDED THAT A DIVERSION TO ZZZ2 WAS THE SAFEST COURSE OF ACTION. I NOTIFIED THE DISPATCHER AND HE CONCURRED. TO ENSURE AN UNIMPEDED AND EXPEDITIOUS LNDG I DECLARED A LOW FUEL EMER WITH ATC. WE WERE CLRED DIRECT TO ZZZ2. WE LANDED A FEW MINS LATER WITH WELL MORE THAN OUR RESERVE FUEL AVAILABLE IN THE INNER WING TANKS. THE APCH AND LNDG WERE OTHERWISE UNEVENTFUL. UPON ARR AT THE GATE I WROTE UP THE MALFUNCTIONS IN THE MAINT LOG. ZZZ2 MAINT MET THE ACFT; AND AFTER REFUELING AND APPLYING AN MEL TO THE FUEL SYS WE COMPLETED THE LEG TO ZZZ3 WITH NO FURTHER DIFFICULTIES. THIS ENTIRE EVENT WAS IN RESPONSE TO A MECHANICAL MALFUNCTION IN THE FUEL SYS OF THE ACFT.