Inhomogeneities in Tokamak peripheral plasmas due to localized recycling of neutrals (plasma fuelling) are considered. A dense cloud of cold charged particles arises in the vicinity of such a localized particle source, for example a gas-puffing valve, as the plasma density exceeds a certain critical level. A dependence of the critical density on such parameters as dimensions of the device, heat flux from the discharge core and diffusivity of charged particles at the edge is found. The results of calculation are compared with experimental data.