nuclear-news

Iran’s uranium enrichment: myths, realities, and what Canada should understand

Canadians deserve an informed debate about the potential proliferation dangers of these new reactor designs, especially as the intention is to export them around the world.

BY ERIKA SIMPSON, GORDON EDWARDS | June 29, 2025, https://www.hilltimes.com/story/2025/06/29/irans-uranium-enrichment-myths-realities-and-what-canada-should-understand/465192/

Confusion and misinformation continue to shape public discussion about uranium enrichment in Iran. As tensions rise in the Middle East and the fear of nuclear weapons proliferation returns to the headlines, it is important for Canadians to understand the basic scientific facts, the real risks, and the broader international implications.

Uranium enrichment sounds mysterious, but is a well-understood process. Natural uranium contains only 0.7 per cent uranium-235, the rare variety of uranium that can undergo the kind of nuclear chain reaction needed for nuclear power or nuclear bombs. The other 99.3 per cent is uranium-238, a heavier variety of uranium that  cannot sustain such a chain reaction. Enrichment is simply the process of raising the percentage of uranium-235.

It is often reported that 90 per cent uranium enrichment is “needed” to have a nuclear weapon. This is not true. The Hiroshima bomb had only 80 per cent enrichment. Iran has a good deal of 60 per cent enriched uranium, and one can make a powerful bomb from 60 per cent enriched uranium. It would be larger in size than a bomb with 90 per cent enrichment, and so more challenging to deliver, but not much more so. The recent bombings are unlikely to have destroyed the hundreds of kilograms of 60 per cent enriched uranium already in Iran.

The mechanism needed for making an atomic bomb from uranium is much simpler than that needed for a plutonium bomb. It’s called a “gun-type” atomic bomb rather than an “implosion-type” atomic bomb. 

The gun-type bomb just fires one chunk of uranium into another chunk (the target) so that the two chunks add up to more than a “critical mass.” It is so simple it cannot possibly fail. The United States never tried out this type of bomb before using it; it was dropped on the city of Hiroshima, Japan, with no prior testing. Such a bomb needs a precision-timed “neutron source,” but that is old technology, well known for a long time.

The implosion-type bomb is needed when plutonium is the nuclear explosive. Implosion is much more demanding. It requires a perfectly spherical mass of plutonium metal surrounded by concentric plastic explosives to drive the sphere inward toward the centre—an “ implosion.”  It is so tricky it’s pretty well got to be tested first. The U.S. detonated one such plutonium bomb at Alamagordo, New Mexico, three weeks before dropping another one on the Japanese city of Nagasaki.

Nuclear authorities maintain that a powerful nuclear explosive device (gun-type) could be made with any uranium enriched to 20 per cent or more. At the 20-per-cent level such a device would be a lot bulkier; it could not easily be carried by rocket or aeroplane, but could be delivered in the hull of a ship, in a truck or cargo container, or even in the trunk of a car, and detonated by remote control. 

For this reason, highly enriched uranium—which is uranium with 20 per cent enriched or more—is increasingly being prohibited from most civilian use.

Up to now, all operating power reactors fuelled with uranium use an enrichment level of no more than five per cent. Fuel at that level of enrichment is not weapons-usable material. But some new reactors proposed in Canada and elsewhere demand fuel that is a lot more enriched. The ARC sodium-cooled reactor planned for New Brunswick uses uranium fuel enriched to more than 13 per cent, while the eVinci reactor being studied in Saskatchewan is designed to use 19.9 per cent enriched uranium.

Independent experts have pointed out that uranium enriched to such high levels—between 12 per cent and 20 per cent—could also be used (like highly enriched uranium) to make an enormously destructive nuclear explosive device. This danger is not officially acknowledged by regulators, and is generally not recognized by politicians and other decision-makers in Canada. The nuclear fuel needed for some of the “fast” or “advanced” SMNRs being proposed in this country is weapons-usable material even though it is below the 20 per per cent enrichment level, and is, therefore, not classified as highly enriched uranium.

Canadians deserve an informed debate about the potential proliferation dangers of these new reactor designs, especially as the intention is to export them around the world.

Gordon Edwards is a nuclear safety consultant and president of the Canadian Coalition for Nuclear Responsibility. Erika Simpson is an associate professor of international politics at the University of Western Ontario.

July 2, 2025 - Posted by Christina Macpherson | Uranium