A DISPATCHER RPTS THAT HE AND THE CAPT OF A B737 AGREED THAT FUEL BOOST PUMPS COULD BE CHANGED BY MAINT SO THAT THE INOP PUMP WOULD BE ON A WING TANK AND THAT WOULD REDUCE THE REQUIRED UNUSABLE FUEL. THIS WAS DONE; BUT A SUPVR DECIDED THAT THE ACFT SHOULD MAKE A FUEL STOP AS A PRECAUTION. THE RPTR DISAGREED WITH THE NECESSITY.

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ACFT HAD AN INOP CTR BOOST PUMP (1 OF 2) WHICH WOULD HAVE MEANT A 15000+ LB PENALTY ASSUMING THE OTHER PUMP MIGHT QUIT. AFTER CONVERSING WITH MAINT AND ASKING IF WING/CTR PUMP WERE INTERCHANGEABLE; THEY RESPONDED YES. BTWN CAPT AND DISPATCHER IT WAS DECIDED TO SWITCH PUMPS AND TAKE AN 8600 LB PENALTY INSTEAD. CAPT AND DISPATCHER TALKED ABOUT THE 8600 LBS BEING UNUSABLE AND IF FOR ANY REASON FUEL BURN WAS OFF OR CAPT FELT BETTER WE WOULD LAND AT EITHER KANSAS CITY; ALBUQUERQUE; PHOENIX; OR LAS VEGAS FOR FUEL. CAPT AGREED AND FELT COMFORTABLE AND ALSO DEP FUEL LOAD WAS BROUGHT UP TO 38300 LBS FROM 36300 LBS MAKING A 10000 LB ARR FUEL LOAD. CAPT WAS ALSO REQUESTED TO KEEP DISPATCH ADVISED DURING HIS FLT ON FUEL CONDITIONS; WITH THIS IN MIND AND PLANNED BOTH PARTIES AGREED. AT APPROX XA37 I WAS QUESTIONED BY SHIFT MGR AS TO WHAT I WAS DOING WITH THAT FLT AND DID I CONSIDER THE 8600 LBS UNUSABLE FUEL. I RESPONDED THAT I WAS USING THE 3800 LB RESERVE AND 4400 LBS EXTRA TO MAKE UP MY 8600 LBS UNUSABLE FUEL AND WAS TOLD TO LAND ACFT IN LAS VEGAS FOR FUEL. I EXPLAINED THAT THE FLT WOULD ARRIVE LAX WITH 10000 LBS AND WAS TOLD TO LAND AGAIN. I CONTACTED FLT; ADVISED THEM OF WHAT WAS DECIDED BY MGR. FLT LANDED LAS VEGAS; FUELED; AND DEPARTED FOR LAX. MEL STATES 8600 LBS OF UNUSABLE FUEL MUST BE MAINTAINED IN ACFT (4800 LBS IN AFFECTED SIDE AND 3800 LBS IN OTHER SIDE LESS 1000 LB IMBAL). RESERVE CANNOT BE PLANNED TO BE USED PLUS EXTRA (3800 RESERVE + 4500 EXTRA = 8300) WAS NOT GOING TO BE USED AS AGREED UPON BY CAPT AND DISPATCH. I FEEL THERE WAS NO SAFETY ISSUE INVOLVED AND ALSO THERE SEEMS TO BE A VERY GRAY AREA AS FAR AS MEL; WHETHER IT'S RESERVE AND UNUSABLE OR NOT. I FEEL I HAVE NOT VIOLATED ANY FARS IN PERFORMANCE/OP OF THIS FLT.