B15, it is not the fuel that goes bang it is the ullage, the fuel/air vapours in the fuel tank. A chain reaction causes a huge overpressure in the fuel tank which is explosive. Quickest and cheapest method of protecting the fuel tank is to fit OBIGGS. This purges the ullage of oxygen and replaces it with nitrogen, inerting the space. Beags has some photos of an airliner that was hit with a SAM and suffered a fuel tank explosion.