It leads to nuclear weapons proliferation (no it doesn't)

In a March 2017 SCIENTIFIC AMERICAN interview, John Holdren, President Obama's Science Advisor, said ``... breeder reactors... [require] what amounts to a plutonium economy... and trafficking in large quantities of weapons-usable material.''

A plutonium economy unrelated to breeder reactors already exists. The often-repeated hyperbole ``trafficking in large quantities of weapons-usable material'' is nonsense.

Used fuel from a British municipal reactor was used to make a nuclear explosion. The yield was a fraction of the Hiroshima weapon, which was a much simpler uranium device. The British remarked ``We will not try that again.''

If plutonium is less than 93% isotopically and chemically pure ²³⁹Pu, explosive yield decreases rapidly. Plutonium in used fuel is never isotopically pure, and never chemically pure in an IFR-type system. Separating isotopically pure ²³⁹Pu from used fuel presents a much more difficult problem than for uranium. Plutonium isotopes in used fuel, other than ²³⁹Pu, emit 50 times more heat, 5,000 times more neutrons, and 100 times more gamma radiation. This could damage a weapon or cause predetonation, and makes maintenance of fine mechanical tolerances difficult. Expensive remote assembly is mandatory. A 1994 Lawrence Livermore National Laboratory study stated ``spent IFR fuel cannot be used to make a nuclear weapon without significant further processing.'' No one makes weapons from used fuel because it is the most difficult substance from which to do so.

Producing isotopically pure plutonium directly in a reactor requires controlling the neutron energy more precisely than is practical in a municipal reactor, and irradiating the fuel for durations far shorter than would be economical. Even the most rudimentary inspection regime would detect this. If an inspection regime is not practical in rogue states, don't sell them reactors, used fuel, or means to reprocess fuel.

Even if truly ``weapons-ready'' material existed, the proliferation argument is a red herring. No country's nuclear power stations or fuel reprocessing affect any other country's desires, decisions, or ability to acquire nuclear weapons. On-site reprocessing implies very few opportunities for diversion or theft. Plutonium in used fuel in an IFR-type system is in a highly-radioactive and therefore easily monitored state. Advanced industrial economies already have nuclear weapons, or have the means to make them much more effectively than from used municipal reactor fuel. Only a fast-neutron reactor can consume all fissionable actinides in used fuel and decommissioned weapons.