Editing Integral fast reactor (section)

===Proliferation===
{{See also|reactor grade plutonium}}
IFRs and [[light-water reactor]]s (LWRs) both produce [[reactor grade plutonium]] – which even at high [[burnup]]s remains weapons-usable<ref>[https://www.belfercenter.org/sites/default/files/files/publication/mmup.pdf Managing Military Uranium and Plutonium in the United States and the Former Soviet Union], Matthew Bunn and John P. Holdren, Annu. Rev. Energy Environ. 1997. 22:403–86</ref> – but the IFR fuel cycle has some design features that make proliferation more difficult than the current [[PUREX]] recycling of spent LWR fuel. For one thing, it may operate at higher burnups and therefore increase the relative abundance of the non-fissile, but fertile, isotopes [[plutonium-238]], [[plutonium-240]], and [[plutonium-242]].<ref>[http://info.ornl.gov/sites/publications/Files/Pub37993.pdf Categorization of Used Nuclear Fuel Inventory in Support of a Comprehensive National Nuclear Fuel Cycle Strategy]. page 35 figure 21. Discharge isotopic composition of a [[pressurized water reactor]] fuel assembly with initial U-235 enrichment of 4.5 wt % that has accumulated 45 GWd/MTU burnup. Isotopic composition of used nuclear fuel as a function of burnup for a generic PWR fuel assembly.</ref>

Unlike PUREX reprocessing, the IFR's electrolytic reprocessing of [[spent fuel]] does not separate out pure plutonium. Instead, it is left mixed with minor actinides and some rare earth fission products, which makes the theoretical ability to make a bomb directly out of it considerably dubious.<ref name="youtube.com"/>{{better source|date=July 2014}} Rather than being transported from a large centralized reprocessing plant to reactors at other locations – as is common now in France, from [[La Hague]] to its dispersed nuclear fleet of LWRs – the IFR pyroprocessed fuel would be much more resistant to unauthorized diversion.<ref name="ReferenceB"/>{{better source|date=July 2014}} The material with the mix of [[plutonium isotopes]] in an IFR would stay at the reactor site and then be burnt up practically ''in-situ'';<ref name="ReferenceB"/>{{better source|date=July 2014}} alternatively, if operated as a breeder reactor, some of the pyroprocessed fuel could be consumed by the reactor (or other reactors located elsewhere). However, as is the case with conventional aqueous reprocessing, it would remain possible to chemically extract all the plutonium isotopes from the pyroprocessed fuel. In fact, it would be much easier to do so from the recycled product than from the original spent fuel. However, doing so would still be more difficult when compared to another conventional recycled nuclear fuel, [[MOX]], as the IFR recycled fuel contains more fission products and, due to its higher [[burnup]], more proliferation-resistant [[Pu-240]] than MOX.

An advantage to the removal and burn up of actinides (include plutonium) from the IFR's spent fuel is the elimination of concerns about leaving spent fuel (or indeed conventional – and therefore comparatively lower [[burnup]] – spent fuel, which can contain weapons-usable plutonium isotope concentrations) in a [[geological repository]] or [[dry cask storage]], which could be mined in the future for the purpose of making weapons.{{sfnp|U.S. Congress|1994|p=30}}

Because reactor-grade plutonium contains isotopes of plutonium with high [[spontaneous fission]] rates, and the ratios of these troublesome isotopes (from a weapons manufacturing point of view) only increases{{Confusing-inline|reason=How can an *increase* in the Pu isotope ratio make the spent fuel more difficult to use for weapons? This seems backwards. Wouldn't more burnup imply less usable Pu for weapons?|date=July 2024}} as the fuel is burnt up for longer and longer, it is considerably more difficult to produce fission nuclear weapons of substantial yield from highly burnt up spent fuel than from (conventional) moderately burnt up LWR spent fuel.

Therefore, proliferation risks are considerably reduced with the IFR system by many metrics, but not entirely eliminated. The plutonium from advanced liquid metal reactor (ALMR) recycled fuel would have an isotopic composition similar to that obtained from other highly burnt up [[spent nuclear fuel]] sources. Although this makes the material less attractive for weapons production, it could nonetheless be used in less sophisticated weapons or with [[fusion boosting]].

In 1962, the U.S. government detonated a nuclear device using then-defined "[[reactor-grade plutonium]]", although in more recent categorizations it would instead be considered as [[reactor grade plutonium#Classification by isotopic composition|fuel-grade plutonium]], typical of that produced by low burn up [[Magnox reactor]]s.<ref>{{cite web |author=WNA <!--contributors --> |url=http://www.world-nuclear.org/info/inf15.html |title=Plutonium |publisher=World Nuclear Association |date=March 2009 |access-date=2010-02-28 |archive-date=2010-03-30 |archive-url=https://web.archive.org/web/20100330221426/http://www.world-nuclear.org/info/inf15.html |url-status=dead }}</ref>{{sfnp|U.S. Congress|1994|p=34}}

Plutonium produced in the fuel of a breeder reactor generally has a higher fraction of the isotope [[plutonium-240]] than that produced in other reactors, making it less attractive for weapons use, particularly in first-generation [[nuclear weapon design]]s similar to [[Fat Man]]. This offers an intrinsic degree of proliferation resistance. However, if a blanket of uranium is used to surround the core during breeding, the plutonium made in the blanket is usually of a high [[Pu-239]] quality, containing very little Pu-240, making it highly attractive for weapons use.<ref>https://www.fas.org/nuke/intro/nuke/plutonium.htmBreeder reactors {{Webarchive|url=https://web.archive.org/web/20130701133701/http://www.fas.org/nuke/intro/nuke/plutonium.htm |date=2013-07-01 }}</ref>

If operated as a breeder instead of a burner, the IFR has proliferation potential:<blockquote>Although some recent proposals for the future of the ALMR/IFR concept have focused more on its ability to transform and irreversibly use up plutonium, such as the conceptual [[PRISM (reactor)]] and the in operation (2014) [[BN-800 reactor]] in Russia, the developers of the IFR acknowledge that it is 'uncontested that the IFR can be configured as a net producer of plutonium'.{{sfnp|U.S. Congress|1994|p=32}}

If instead of processing spent fuel, the ALMR system were used to reprocess ''irradiated [[fertile material|fertile (breeding) material]]'' [that is, if a blanket of breeding U-238 was used] in the electrorefiner, the resulting plutonium would be a superior material, with a nearly ideal isotope composition for nuclear weapons manufacture.{{sfnp|U.S. Congress|1994|p=36}}</blockquote>