Performance of Large Breed-and-Burn Core

A sodium-cooled fast reactor breed-and-burn (B&B) core and fuel cycle concept are proposed to achieve uranium utilization in the vicinity of 50% without separation of most of the fission products from the actinides. This core is to be fueled with depleted uranium (DU) with the exception of the initial core loading that uses fissile fuel to achieve initial criticality. When the cladding reaches its radiation damage limit, the melt-refining process is used to recondition the fuel, and then the fuel is reloaded into the core. This fuel reconditioning continues until the fuel reaches the neutronically maximum attainable burnup. When a fuel assembly is discharged at its maximum attainable burnup, it is replaced with a fresh DU assembly.

The maximum burnup attainable in a large 3000-MW(thermal) B&B core is found to be 57% fissions per initial metal atoms (FIMA). The discharged fuel characteristics such as the inventory of actinides, radiotoxicity, and decay heat are one order of magnitude smaller, per unit of energy generated, than those of a light water reactor operating with the once-through fuel cycle.

It is also found that the minimum burnup required for sustaining the B&B mode of operation is 19.4% FIMA. The fuel discharged at this burnup has sufficient excess reactivity for establishing initial criticality in a new large B&B core. The theoretical minimum doubling time for new core spawning is estimated to be [approximately]10 effective full-power years; there is no need for any external fissile material supply beyond that required for the initial "mother" reactor.

Successful development and deployment of the B&B core along with fuel reconditioning could possibly provide up to 3000 yr worth of the current global nuclear electricity generation by using the DU stockpiles already accumulated worldwide. However, a number of important feasibility issues are yet to be resolved.