**4.1. Variants of campaigns for figures 2, 3, 4**

Let us compare some campaign characteristics of three shown variants of reactors with different fuel type, which are significant for its working out for applying in practice. This comparison is needed because the choice of initial conditions for campaign characteristics calculation is, in principle, not equivalent. Comparisons can delete this shortage.

Portion of raw uranium usage is usage rationality of this fuel kind (at this campaign). It is important because uranium is unique natural material containing fission isotope 235U.

Only the first of three considered campaigns can be used in the open cycle, i.e. without nuclides, which were gotten from the spent fuel.

Closed fuel cycles with raw thorium or raw uranium can work without 235U usage. Thus, the complete use of natural uranium, which used at the initial stages of these campaigns, is reached.

At the base of 238U+235U fuel simplest campaign cannot reach high raw uranium usage. Reproduction of fission materials is too small, neutron losses in reactor control elements is too big. Reached burn-up is minimal among all suggested variants.

## **4.2. Variants with equilibrium fuel**

Characteristics of reactors campaign with initial contents of 239Pu and 241Pu sum in the uranium-plutonium fuel, which is equal to equilibrium, which can be formed from the campaign by picture 3, are presented at string 4 of application's table 1.

Fission reproduction coefficient in this campaign is equal to unity practically always during campaign. Neutron absorption in control rods increases up to 3.3 %. Reactor power is practically constant. Its decrease is not more than 1 %.

Optimization of campaign with fuel on the base 233U + 232Th by the same means is also interesting. These data are shown at string 5 of application's table 1.

Equilibrium of fission materials in the campaign with equilibrium contents of 233U, 235U and thorium is achieved after 2000 work hours. Neutron absorption in control rods is 5.8 %. Reactor power decreases to 93.2 % from initial value at 2000 work hours and remains stable. Power decrease is caused by 233U formation and role of 233Ра with long half-time.

Large reactivity margin with increase possibility of neutron losses in construction materials and for leakage is significant difference between this and previous campaign.
