A red flag went down when I read this Fox News revamp of an AP story about 8kg of missing uranium in China:
Authorities said that 17 pounds of weapons-grade uranium disappeared and that a verdict in the trial of four men accused of trying to sell the radioactive material will be delayed until it is found, state media reported Friday.
That's a big loss of face, so much so that I'd have to believe that China had developed a free press in order to believe that an official said "weapons-grade", as well as more government transparency in order to try such thieves publicly. As it turns out, the state media claim was worded differently:
Jiang Chaoqiang, director of the Guangzhou No 12 People's Hospital, told China Daily: "The radioactive substance uranium does not explode when it is in its raw state, but it is very harmful to people's health."
That's "raw" as in "unrefined". On the other hand, "weapons-grade" is typically 90%+ U-235. Unrefined uranium is mostly U-238, which isn't useful for bombs. It has to be refined to be "reactor grade". I turned to MSNBC for some actual numbers about uranium:
Uranium enriched to between 3.5 percent and 5 percent is used to make fuel for reactors to generate electricity. It becomes suitable for use in nuclear weapons when enriched to more than 90 percent.
There's a big difference between 5% and 90%. Assuming that the uranium was indeed being illegally sold from a mine as purported by state media, I'd expect it to be reactor grade at worst; weapons-grade refining would almost certainly be performed at government-controlled facilities in China and under tight scrutiny. A paltry 8kg is far from critical mass, weapons grade or no, but it could make for a hefty dirty bomb payload.
There's another odd aspect to the case, people allegedly falling sick.
More than 20 people had fallen sick after being exposed to the radioactive material, the Hong Kong-based Information Center for Human Rights and Democracy said, citing an official involved in the investigation.
It also appears that the "weapons-grade" claim originates from democratic opposition (single source), not a state mouthpiece.
Regardless of whether the uranium is reactor-grade or weapons-grade, the people stealing it were apparently ignorant of how to guard against radiation if some accounts are to be believed. It's not hard to shield even enriched uranium, given this example:
Had the 15-pound uranium cylinder been weapon-grade highly enriched uranium instead of depleted uranium (which is not suitable for nuclear weapons), the dose rate at the surface of the highly enriched uranium would have been more than 100 times higher. However, nearly all of this increase would be due to alpha radiation, which can be shielded with a sheet of paper. Meanwhile, the beta-ray dose rate would be about the same or lower and the gamma-ray dose would be ten or more times higher. At the surface of the shielded container the dose rate would be be about one to ten times higher. The dose rate of the highly enriched uranium cylinder could be easily reduced to that of the shielded depleted uranium container (i.e., 0.5 mrad/hr) by adding an additional 1/8 inch of lead (one-third of a centimeter) around the cylinder. This would add only about 6.6 pounds (3 kilograms) to the mass of the lead shielding.
If people did come down with radiation sickness, then this wasn't a knowledgable outfit trying to fence uranium.
An Australian newspaper carries an additional claim:
Police have recovered only 35 grams of uranium from the four men. They claimed a fifth partner, Zhang Xinfang, had disappeared with the bulk of the uranium and had since become seriously ill, presumably from exposure to the radioactivity.
I can't tell if that's a cover story agreed on by the thieves or not, but I wouldn't put a lot of trust in them. For all I know, they might face swift execution if the uranium is found in toto.
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