A recent addition to the list of emergent materials is the ReBaCo4O7+delta family of compounds. Indeed, due to the magnitude of their oxygen uptake and release capability, they are very promising materials for applications ranging from solid-oxide fuel cells to gas-separation membranes and oxygen sensors. Whilst there is no doubt that YBaCo4O7+delta can accommodate oxygen up to delta= 1.5, the mechanisms behind this huge uptake is unclear. Although there has been some success in stabilizing structures with high delta values, in-situ studies are clearly needed to understand the process. So far, these in-situ studies have only been performed with X-rays and the amount of information obtained on the oxygen has intrinsically been limited. We therefore propose to perform in-situ neutron diffraction study of the oxygen absorption in YBaCo4O7+delta.