**8.3. Open fuel cycle**

Open fuel cycle can be realized by the initial fuel, which consists of 235U and 238U. This fuel can contain natural uranium, as in CANDU reactors, enriched uranium, as in the majority of modern reactors, and, as it presented on the calculation above, from the 235U impoverished. Fission materials in all of these cases are made from natural uranium passing the chains, which is bounded with recycling of spent fuel. Let's assume that technology of 233U generation is not bounded with recycling of spent fuel and might take the part in opened fuel cycle.

The final product of open fuel cycle can be the perfect base or composite part of closed fuel cycle. Especially, if fission isotopes of plutonium come to equilibrium.

Open cycles, which are presented in strings 1, 9, 10, 12 -15, 17, 23 and 24 of Attachment Table 1, are described above. Maximum portion of natural uranium usage on it is reached under the conduction of superposition mode areas with 233U generation. Quite high part of using is reached in the superposition mode under the decreased neutrons losses in construction materials and for leakage. In these cases fission isotopes of plutonium are in equilibrium at campaign end. Maximal reached part of natural uranium using in presented cycles forms 5.27%. This amount in cycles with generation of 233U can be increased at the expense of generation mode optimization. Optimization is not appeared by paramount task at this work.

Thereby, there are different ways for reaching of high natural uranium usage in open fuel cycles and reception of closed fuel cycles fission components on its.
