Net non-proliferation impact of mandating plutonium for fast reactors under lower enrichment limits

Determine whether limiting uranium enrichment to levels that render uranium-fueled fast-spectrum reactors unviable, thereby necessitating plutonium fuel for fast-spectrum reactors, yields a net benefit for nuclear non-proliferation compared to allowing higher-enrichment uranium (high-assay low-enriched uranium, HALEU) in such reactors.

Background

The paper critiques proposals to lower civilian uranium enrichment limits below 20% on the grounds of potential weapons risks posed by HALEU. In discussing reactor design impacts, the authors emphasize that fast-spectrum reactors generally require higher fissile loadings and would be directly affected by such limits.

They argue that imposing lower enrichment limits could either make uranium-fueled fast reactors impossible or force them to use plutonium instead. They explicitly express uncertainty about whether this shift would improve or harm non-proliferation outcomes, framing it as an unresolved question about net non-proliferation benefit.