The great enhancement of the minority carrier recombination rate after optical activation of FeB pairs was used for investigation of interstitial Fe ions diffusion in p-type Czochralsky silicon by Surface Photo-Voltage Technique (SPV). Highly reproducible profiles of the Fe ions distribution were obtained after one-time thermodonors annealing process (650 °C, 30 min.) with Fe film evaporated on one side of silicon slab and successive layer by layer silicon slab etching. Evolution of Fe concentration distribution between both sides of initially inhomogeneously contaminated silicon slab in durable annealing processes was investigated. Gradual Fe concentration reduction near preliminary contaminated slab surface and Fe concentration increase near opposite surface were observed. Fe concentrations near both surfaces become equal after approximately 10-times annealing in agreement with diffusion rate obtained by the first method. Chaotic release and hiding of latent Fe were observed after 5-7 hours of annealing process. Two-exponential increase of other than Fe recombination centers concentration was observed during 650 °C annealing. Both exponential factors are found to be functions of interstitial oxygen concentration in the silicon ingot.