> Burning HALEU is a perfect example of this, as if you do that, especially in a fast reactor where you need high fissile concentration, you can make fuel more

> Burning HALEU is a perfect example of this, as if you do that, especially in a fast reactor where you need high fissile concentration, you can make fuel more than 50% of total costs. The way I think breeder might make sense today for a new commercial design (without a government funded reprocessing program) is if you have a design with a breeding ratio slightly over 1 enabling very high burnups without reactivity swing (iso-breeding, breed-and-burn, or whatever you want to call it). Of course, that requires a fuel design that won't fall apart at high burnups. IIRC EBR-II metallic fuel reached up to 200 GWd/tHM, and of course fast spectrum molten salt designs like Elysium have no such limits at all. But yeah, for thermal reactors with no plans for reprocessing, much higher enrichments than the current LWR standard is most likely not justified, in my non-expert opinion. > Page 413 of Hewlett and Holl's Atoms for Peace and War: https://www.energy.gov/management/downloads/hewlett-and-holl.. https://www.energy.gov/management/downloads/hewlett-and-holl.... Thanks, looks like an interesting book (though not really much details why Zinn thought the way he did..).