Its one fo the smallest tanks on the ac. In between the rear wing area and the fuselage (on both sides). If I can 2nd guess where you're referring to TD, and if memory serves me right, that was where the "seals were melted" (according to panorama tv) on XV227. The heat had had sufficient time to melt some of the PRC sealant in the starboard side 7 tank.
Hope this helps