Seite 16/25 Fertile Free Fuel  very step burnup curve of fertile free fuel caused by rapid burning of fissile material  high excess reactivity would be required in solid fuel reactors to reach acceptable cycle time  high excess reactivity requires a strong control system   strong initiator for transient over power accidents caused by malfunction of control system  high Pu content tends to degrade Pu quality  breeding of higher Pu and MA isotopes  unknown reprocessing strategies for different inert matrix fuel types Solutions:  fast power reactors – isobreeder core, breeding compensates burnup and allows long cycle times, weak control assemblies, and breeding of fresh Pu  online re-fuelling compensates reactivity loss continuously
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