Investigation of the Neutronic Potential of Moderated and Fast (D,T) Hybrid Blankets for Rejuvenation of CANDU Spent Fuel

The potential of moderated and fast hybrid blankets is investigated for the rejuvenation of CANDU spent fuel. The moderated hybrid blanket has revealed poor neutronic performance and is not suitable for CANDU spent-fuel rejuvenation. The fast-fissioning hybrid blanket has excellent neutronic performance and is investigated to achieve different enrichment grades of fissile isotopes (EGFI) for three different applications:

1. recycling in a conventional commercial CANDU reactor (EGFI = 0.71 to 0.9%)
2. recycling in an advanced CANDU reactor concept with high burnup rate (EGFI = 1%)
3. recycling in an advanced breeder with thorium fuel (EGFI > 1.5%)

For fast-fissioning blankets, a rejuvenation period of up to 24 months is investigated by a plant factor of 75% under a first-wall (deuterium, tritium) fusion neutron current load of 10¹⁴ to 14 MeV·n/cm²·s, corresponding to 2.25 MW/m². Rejuvenation periods of 6 to 12 months, 10 to 16 months, and 18 months, respectively, are evaluated for the above-mentioned reactor types. The blanket energy multiplication M increases only by ∼20% in 24 months; i.e., the electricity production remains fairly constant during this period. Consequently, this power plant exploits the nonnuclear island very well. At the same time, the peak-to-average fission power density ratio decreases by ∼9.1%.