B747-400 Captain reported observing uncontrollable fuel transfer from main tank four to the center tank at the rate of approximately 100 kilograms per 11 minutes or approximately 600 kilograms per hour. The flight crew determined it was impossible to continue to destination airport due to insufficient fuel remaining. The flight crew requested priority handling and performed an air turn back and precautionary landing at departure airport.

Narrative

Website reflected an issue was written up on Day 0 with a due date of Day 2 for uncontrolled fuel transfer from tank four to the center tank. I spoke with Dispatch before leaving the hotel regarding the maintenance item appearing to be active in the website and was informed the only active MEL was the APU.Upon arrival at the airplane; the inbound crew relayed they had experienced an uncontrollable fuel transfer for their flight between ZZZ1 and ZZZ but that it was minor. I discussed this issue with Local Maintenance and was told this aircraft has a history of that problem; but it is intermittent. During pre-flight a puddle was observed below engine 4 and was thought to be hydraulic fluid from servicing. It was night.Armed with all of that information; we monitored the fuel page immediately after departure. We observed uncontrollable fuel transfer from main tank four to the center tank at the rate of approximately 100 kilograms per 11 minutes or approximately 600 kilograms per Hour. By the second hour of flight and with no change to the condition; we were observing the need for balancing fuel between 1 and 4. Tank 4 was continuing to transfer its fuel to the center tank. We consulted the QRH; determined at that time no fuel was being lost overboard and balanced fuel accordingly. We consulted with Dispatch and the Chief Pilot via SATCOM regarding the situation. We discussed the potential for loss of all fuel in tank number four under the current conditions and the potential for #4 engine loss during configuration for landing in ZZZZ. We received message that after consulting with an engineer; evaluating the curfew for alternatives in ZZZZ1; and the overall situation that we were going to return to ZZZ. We had flown approximately 2.7 hours at this point. Note: departure fuel level 122 tons. At approximately 80-85 tons; with no center tank fuel remaining; the uncontrollable loss from tank 4 reduced to approximately 100 kilos per 22 minutes and appeared to be going overboard.We informed ATC of our divert and rerouted back to ZZZ. While enroute; ZZZ ATC informed us they had [requested priority handling] for our aircraft. We downgraded the situation. We determined we would be below maximum landing weight and set ourselves up for the ILS approach to Runway X left at ZZZ's request. Flaps 30; brakes 3; full reverse.After landing; and during thrust reverser operation we experienced intermittent smoke crew rest EICAS messages; haze on the flight deck; and an acrid odor. As we exited the runway on Taxiway X; I directed one crew member to determine if there was a fire in the crew rest area in preparation to park on Y and exit the aircraft. He returned with information of no fire but haze and odor on the flight deck. I directed him down to the main deck with an oxygen bottle to see if there was a fire on the main deck considering the hazmat we had onboard. He returned with information of no fire but haze on the main deck as well. I informed Ground Control of smoke/fumes on the flight deck during the landing roll but that the issue was dissipating as soon as we cleared the runway. I also observed a hazy cloud over the runway as we turned parallel onto Taxiway Y. As a precaution; fire trucks and equipment escorted us to parking at Company 2. We turned off packs two and three and turned on the flight deck fan switch as a precaution. Pack two subsequently failed and generated a status message. I suspected fuel contamination in the ducting as a potential source of the haze and directed my relief crew member to add it to the logbook along with other items.We were towed into parking with engine 4 running due to the APU MEL. I directed everyone to prepare and get off the airplane immediately after the door is opened. Firemen swept the main deck and upper deck with no finding of fire and reported to me on the flight deck as I discussed the details with Maintenance prior to exiting the aircraft myself. Cause - Kicking the maintenance candown the road.Suggestions - I have no suggestion.