The physics design of a high flux core for the R-5 reactor

In the second phase of operation of the R-5 reactor, there has been a proposal to obtain higher fluxes by loading Pu-Al alloy fuels into the central region of the core. The constraints that have been laid down for the design of this core are the following: (a) the specific power in a natural uranium 28 rod cluster of the Pickering type should be 34 KW/Kg when irradiated in the central loop of the R-5 reactor. (With the present core one gets 15 KW/Kg.), (b) the total power of the reactor should not exceed 100 MW, (c) the fuel channels in the outer zone should not produce more than their rated power, and (d) the total quantity of Pu produced by conversion of uranium-238 in the natural uranium channels should not be less than the total amount of Pu burnt in the Pu-Al alloy fuels in the same length of time. Physics studies have established the feasibility of meeting these four constraints at the beginning of core life and have also provided a fuelling scheme which enables the high flux to be maintained with a reasonable rate of refuelling. The results are presented. (author)