PAPER 2.11 PHYSICS DESIGN OF THE FERMI MIXED OXIDE CORE

SYNOPSIS The analysis of critical experiments is related to the uncertainties in predicting the operating parameters of an oxide core for the Fermi reactor. Preliminary investigation of potential accident situations indicates the reactor to be safe within the range of parameter uncertainties.

The work described in this paper forms part of a program for the demonstration of mixed oxide fuel in the Fermi reactor. The program has been supported mainly by the Edison Electric Institute, BelgoNucleaire (within the framework of the Belgian-State-Euratom agreement on fast reactors), the CRISPI organization of Japan, and The Detroit Edison Co.

The preliminary design calculations for the oxide core have been described in some detail previously (ref. 1, 2). Many of the design results have been strongly influenced by the requirement of placing the new core design into an already existing reactor system. Considerable flexibility both in design and in operation is expected to result from the decision to compensate reactivity loss from burnup by adding fuel subassemblies at the core edge, gradually increasing the core volume from 5^+0 L to S^O L. The required fuel fissile fraction will be about 30#, and the ratio of Pu to U-235 in the fuel will depend on the availability of plutonium at the time of final design specification. The design will