Editing Integral fast reactor (section)

===Fuel cycle===
{{see also|Nuclear fuel cycle}}
[[Fast reactor]] fuel must be at least 20% fissile, greater than the [[low enriched uranium|low-enriched uranium]] used in LWRs. The [[fissile]] material can initially include [[highly enriched uranium]] or [[plutonium]] from LWR [[spent fuel]], decommissioned [[nuclear weapon]]s, or other sources. During operation, the reactor breeds more fissile material from [[fertile material]] – at most about 5% more from uranium and 1% more from [[thorium]].

The fertile material in fast reactor fuel can be [[depleted uranium]] (mostly [[uranium-238]]), [[natural uranium]], [[thorium]], or [[reprocessed uranium]] from [[spent fuel]] from traditional LWRs,<ref name=berkeley/> and even include nonfissile [[isotopes of plutonium]] and [[minor actinide]] isotopes. Assuming no leakage of actinides to the waste stream during reprocessing, a 1 GWe IFR-style reactor would consume about 1 ton of fertile material per year and produce about 1 ton of [[fission product]]s.

[[nuclear reprocessing#PYRO-A and -B for IFR|The IFR fuel cycle's reprocessing]] by [[pyroprocessing]] (in this case, [[electrorefining]]) does not need to produce pure plutonium, free of fission product radioactivity, as the [[PUREX]] process is designed to do. The purpose of reprocessing in the IFR fuel cycle is simply to reduce the level of those fission products that are [[neutron poison]]s; even these need not be completely removed. The electrorefined spent fuel is highly radioactive, but because new fuel need not be precisely fabricated like LWR fuel pellets but can simply be cast, remote fabrication can be used, reducing exposure to workers.

Like any fast reactor, by changing the material used in the blankets, the IFR can be operated over a spectrum from breeder to self-sufficient to burner. In breeder mode (using U-238 blankets) the reactor produces more fissile material than it consumes. This is useful for providing fissile material for starting up other plants. Using steel reflectors instead of U-238 blankets, the reactor operates in pure burner mode and is not a net creator of fissile material; on balance, it will consume fissile and fertile material and, assuming loss-free reprocessing, output no [[actinides]] but only [[fission products]] and [[activation products]]. The amount of fissile material needed could be a limiting factor to very widespread deployment of fast reactors if stocks of surplus weapons plutonium and LWR spent fuel plutonium are not sufficient. To maximize the rate at which fast reactors can be deployed, they can be operated in maximum breeding mode.

Reprocessing nuclear fuel using pyroprocessing and electrorefining has not yet been demonstrated on a commercial scale, so investing in a large IFR-style plant may be a higher [[financial risk]] than a conventional LWR.