26.08.2015   ACCELERATOR DRIVEN SUBCRITICAL REACTORS

Neutronics

The chosen reference value of the multiplication factor is 0.98. However, fuel evolution leads to deviations from the reference. As already mentioned, it is possible to limit these deviations by balancing the reactivity losses due to neutron absorption by fission products by an increase of the fissile nuclei concentration. Figure 12.3 shows the evolution of kef computed with and

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Figure 12.3. Example of the variation of the multiplication coefficient as a function of burn-up [76]. The result of a calculation without absorption by fission products is also shown. In this case, the increase of the multiplication factor is due to the increase of the 233U concentration. This concentration converges towards equilibrium.

without neutron capture by fission products. The initial decrease of k is due to the building up of the 233Pa inventory.

The reference total thermal power is 1500 MW, corresponding to an electric power of 635 MW. The specific power is around 500 kW/l. The fuel initial mass amounts to 30 tons with 10% of 233U. The foreseen burn-up for an in-pile lifetime of 5 years is 100 GWd/ton, which is equivalent to 10% of the initial load.