Sorry I can't be of too much assistance in this, in that I only have fairly basic info on the A340-300 and here are a few guideline figures, from which you will see it's quite difficult to give one figure. As you know, it depends on weight and altitude and of course, an aircraft flying a long haul trip will use a lot more fuel early on, because of the very weight of that fuel.
expressed as KG/Hr per engine (i.e multiply by four!)
Weight 200t, FL 240 (the highest I have here!)
1633 (or 6532 total).
At 250t, the consumption is 1906, or 7624 total, again for 240.
Alternatively, a lighter aircraft, at 180t, at 160, (for example, flying from Dublin to Shannon) would burn just under 1400, or 5600t total. Obviously, for a long flight, well into the cruise, you would be looking at a figure of much less than the 7624 listed above, although you might well start off with this sort of burn and average about 6.5-7 tons per hour over an 11 hour trip (this is rather rough guesswork), so based on this an aircraft on such a flight, eg from JNB to Madrid would require:
Hold 5 (based on 170t at FL120 for 1 hr)
Divert 5 (based on diversion to BCN at 240)
Not really what you wanted I know, but I hope it points you in the right direction at least.