Japan Airlines is giving more details about a fuel leak on one of its Boeing 787s that delayed a nonstop flight from Boston to Tokyo. A spokeswoman said one of four valves connecting the center and left main fuel tanks was open. That led to fuel flowing between the center and left tanks to a surge tank near the wing tip and then out a vent, spilling about 40 gallons. She said that valve was deactivated and the flight was cleared to depart later Tuesday. The leak Tuesday was the second problem in two days for Japan Airlines at Logan International Airport. A fire broke out in a battery pack in a different Boeing 787 Monday, after passengers had left the plane.