The life-limiting feature of AGR power reactors is probably radiation damage to the graphite moderators. This proposal (part of a collaborative EPSRC programme - Fundamentals of Graphite) seeks to apply SANS to study the porosity and how it links to radiation damage. Previous SANS measurements on AGR graphites have shown fractal behaviour over a wide Q range - yielding power law scattering with a non-integer index changed by irradiation. This suggests that the SANS is dominated by a single mechanism e.g. by Mrozowski cracks which are created in microcrystalline graphites by anisotropic contraction along the c direction during cooling. Two approaches are proposed to test this hypothesis. (1) contrast matching using H/D-toluene demonstrating how much of the porosity is linked to the surface; (2) variation with temperature, demonstrating the link with the anisotropic thermal expansion.