The US is still regulating some enriched uranium based on an analysis from the 1950s. //

High-assay low-enriched uranium (HALEU) has been touted as the go-to fuel for powering next-gen nuclear reactors, which include the sodium-cooled TerraPower or the space-borne system powering Demonstration Rocket for Agile Cislunar Operations (DRACO). That’s because it was supposed to offer higher efficiency while keeping uranium enrichment “well below the threshold needed for weapons-grade material,” according to the US Department of Energy.

This justified huge government investments in HALEU production in the US and UK, as well as relaxed security requirements for facilities using it as fuel. But now, a team of scientists has published an article in Science that argues that you can make a nuclear bomb using HALEU.

“I looked it up and DRACO space reactor will use around 300 kg of HALEU. This is marginal, but I would say you could make one a weapon with that much,” says Edwin Lyman, the director of Nuclear Power Safety at the Union of Concerned Scientists and co-author of the paper. //

Material that’s under 10 percent uranium-235 is called low-enriched uranium (LEU) and is used in power reactors working today. Moving the enrichment level up to between 10 and 20 percent, we get HALEU; above 20 percent, we start talking about highly enriched uranium, which can reach over 90 percent enrichment for uses like nuclear weapons.

“Historically, 20 percent has been considered a threshold between highly enriched uranium and low enriched uranium and, over time, that’s been associated with the limit of what is usable in nuclear weapons and what isn’t. But the truth is that threshold is not really a limit of weapons usability,” says Lyman. And we knew that since long time ago. //

According to his team, an amount between 700–1,000 kg of HALEU is enough to build a bomb with a 15-kiloton yield—roughly as powerful as the Little Boy bomb that destroyed Hiroshima in 1945. Building one of these bombs would be a matter of days or weeks for a rogue country or a terrorist group.

Somewhere along the way, we dropped the original Los Alamos fine print mentioning quantities and tied our security requirements to enrichment levels only. //

Lyman’s team proposes to get back to the Los Alamos study findings and simply classify HALEU as a Category I material in cases when it’s being used in an amount large enough to build a nuclear weapon. “The point of our article is to highlight that pretending HALEU is not weapons-usable could lead to very serious gaps in security if these reactors really become viable and exported to all sorts of places,” Lyman says. //

SFC Ars Centurion
14y
359
Subscriptor++
So you need 1,000Kg to build a bomb. Let's say an armed foreign adversary managed to attack one of these facilities. Exactly how long is it going to take them to both break into the area where the fissile material is being used, get it out of where it's at, and into something to transport it. That is roughly #2,200 lbs we're talking about. Could you do that with a normal moving van? Absolutely. But can you do it in under an hour, without killing everyone involved via radiation poisoning? I'm skeptical. //

GottaSaySomething Ars Scholae Palatinae
7y
1,342
Ed: I totally missed the point. The point of the article is selling it to "iffy" states where you can't control what happens to it. Not it being stolen from the producing country's reactors. //

Quisquis Ars Tribunus Angusticlavius
12y
6,846
Heads up for the discussion:

1 ton of uranium is only about two cubic feet. //

Pueo Ars Scholae Palatinae
10y
1,005

jandrese said:
I think it's more of a case where terrorists also get centrifuges...

HALEU still poses more of a risk if we're worried about covert enrichment because by the time you're at 20% you've already done about 90% of the separative work necessary to reach weapons grade uranium. This means you have only 10% of the signal or 10% of the time available to catch the covert enrichment of HALEU vs the cover enrichment of natural uranium. //

Atterus Ars Tribunus Militum
6y
1,663
Time to end the technological dark ages caused by nuclear fears. Nearly every issue surrounding the tech is the result of government meddling and red tape along with lying about providing a place to store what little waste there COULD be if reprocessing was allowed. All due to unfounded fear mongering largely based on a shitty film, braindead communist planners in Russia, and a journalist that thought it was scandalous concrete had elevated radioactivity... decades of stagnation as a result. //

Nick31 Seniorius Lurkius
7y
6
I was interested in this, until I saw that the only source was from the Union of Concerned Scientists, the same group who specializes in fear-mongering and hysteria with their ridiculous "Doomsday Clock." In this case they seem to be using their hypothetical disaster scenarios to ask for the last thing the nuclear power industry needs: more government regulations.