What they failed to appreciate, and what the company failed to tell them, was that a fast-breeder uses fuel that has a 19% concentration of the fissile isotope of uranium, 235U. Ordinary nuclear reactors use fuel containing around 3% of the fissile isotope.

ECONOMIST: All over in a flash

Thorium can be used as a nuclear fuel through breeding to fissile uranium-233.

FORBES: Is Thorium the Biggest Energy Breakthrough Since Fire? Possibly.

The prototype light-water reactor that North Korea is constructing at Yongbyon, and which requires enriched-uranium fuel, could add to the fissile material stockpile when it is completed, possibly by the end of the year.

BBC: Yongbyon restart: North Korea ramps up nuclear tension

Uranium enrichment is a process which makes nuclear fuel but can also be diverted to produce the fissile core of atomic bombs.

CENTERFORSECURITYPOLICY: Tehran threat in the US' backyard

It also expelled the weapons inspectors who were monitoring its plutonium-laden spent fuel rods and a reactor capable of producing more that can be reprocessed into fissile material for nuclear bombs.

ECONOMIST: South Korea

Over the past three months, Iran has more than tripled its monthly output of uranium that has been enriched to a fissile concentration of 20% at Natanz and Fordow, according to the IAEA. Such nuclear fuel, compared with the 3.5% used in most nuclear-power reactors, brings Iran dangerously close to the weapons-grade level needed to make atomic weapons, according to nuclear experts.

WSJ: Iran Is Ramping Up Nuclear-Fuel Output