Fast reactors can be used to adjust the isotopic composition of plutonium from spent mixed uranium-plutonium fuel from PWR and make it recyclable. The efficacy of such an adjustment is directly related to the scope for breeding in fast reactors. This can be done in the operating BN-800 reactor by multiple recycling of plutonium in the fuel of the fast reactor as well as by using 235U or in specialized (target) fuel assemblies with reduced plutonium content. The international project with the use of BN-800 will make it possible to experimentally demonstrate this possibility on representative batches of plutonium (up to 100 kg/yr) as well as to work out the particularities of international and national laws in the field of accounting and moving of nuclear materials. A commercially significant project (with a turnover of 1 t or more of plutonium per year) to adjust the plutonium composition can be planned when a series of commercial high-power fast reactors with a heightened breeding ratio is put into operation.