This is a safety question about fuel and fires. This all regards commercial aviation for large passenger planes.
Most fuel is stored in the wings, but in the largest planes, there's also a center tank for the longest flights. It's this center tank I'm concerned with. In the event of a fire, this seems to be the most dangerous tank.
I'm obviously concerned with fires in the fuselage, or very close to it. Obviously this is where all the people are and we don't want smoke or flame there, but remember also there are overhead oxygen canisters that if heated or fueled, will explode.
Jet fuel is flammable by its nature. This cannot be changed because its purpose is to combust in an internal combustion engine. So it seems the best we can do is to keep the fuel as far from the fuselage as possible, to make it unlikely that fuel will cause a fire there (initially).
Isn't there someplace we can move this center tank? Some ideas I thought of: store fuel in anti-shock bodies on the wings (or they could be just small sears-haack bodies on the wings); store fuel in the empannage; store fuel in nacelles that have a larger diameter than the engine itself, to make room for fuel.
Another exotic idea: Is it possible to engineer the wing such that the most likely structural failure will happen first near the wingtip rather than the wingroot? This would spill the fuel farther from the fuselage. (I got this idea from a really wierd Boeing 747 crash in Netherlands where one engine jumped off then fell back into the other engine, causing 2 engine losses. They said some pins were designed to fail first for a more "benign" failure, but apparently those pylon pins were engineered wrong.)
There's one more tricky caveat, though: the cross feed line to balance fuel loads in the wings. If we eliminate this line, we increase the dangerous consequences of a fuel imbalance. But, it's interesting to think of what might cause a major fuel imbalance other than a leak, in which case the cross feed valve should not be opened. I can't think of anything so I'm leaning toward the opinion that this line can be eliminated too.
EDIT: Thanks to bodargpd for pointing this out. Losing an engine in flight means the consumption rates will be hugely different. Without a cross-feed line, all that fuel in the other wing is unavailable and we may have to ditch early. So the cross-feed line is still necessary. I still say this is much less dangerous than a center fuel tank, however. It would also be nice if we engineered the cross-feed line to be weakest at the sides, so any leak will most likely be as far to the outside of the fuselage as possible.
To sum up, the basic question is, can we viably move the center tank volume of fuel somewhere outside the fuselage?
EDIT: I'm not primarily worried about fuel explosions. I'm concerned mostly about fuel leaks during hard emergency landings. I'd rather have a fuel leak out on the wing than in the fuselage.