Paul raises a really important point about North Korea’s uranium conversion capabilities. It’s a timely subject, too.
The fuel fabrication complex at Yongbyon is reported to involve a series of process lines for uranium conversion. Uranium ore concentrate (i.e., yellowcake) is converted to UO3, which is converted to UO2, which is converted to green salt (UF4), which is then converted to metal to produce Magnox fuel rods. (Have a look.)
The metallic fuel is natural (unenriched) uranium, which is cast into cylindrical shapes, machined smooth, and placed inside “cans” made of a magnesium alloy. Here’s how the last conversion step is done in the UK:
Uranium tetrafluoride (UF4) is converted to uranium metal for Magnox fuel by mixing it with magnesium metal. When heated in a furnace to 600oC, the UF4 and magnesium react together. Uranium melts and flows into a catchpot at the bottom of the furnace and a layer of fluoride slag forms on the top. After cooling, the billet of uranium is separated from the slag, remelted, and cast into rods.
And that’s why Yongbyon doesn’t have a UF6 process line (that anyone knows about). Now you know.
Now, as far as anyone knows, the only place this process has taken place in recent years, besides Yongbyon, is the Springfields facility in Preston, Lancashire, England.
This is a timely subject because the IAEA’s latest report on Syria, GOV/2009/6, mainly concerns the uranium traces found at the suspect site in the wadi at al-Kibar (AKA Dair Alzour), which appears for all the world to have been a Yongbyon-style Magnox reactor. It says that
analysis of the environmental samples taken from the Dair Alzour site revealed a significant number of anthropogenic natural uranium particles (i.e. produced as a result of chemical processing)…
Now, perhaps these particles weren’t traces of Magnox fuel or one of the related compounds mentioned above. But if they were from Magnox fuel, there are only three possible sources I can think of:
- Yongbyon (a possibility James has addressed)
- An unknown facility somewhere else
Now consider the following excerpt from the IAEA’s Syria report of November 2008, GOV/2008/60:
14. Satellite imagery and other information available to the Agency concerning installations at the three other locations in Syria referred to above suggest that those locations may be of relevance to the activities at the Dair Alzour site. As indicated above, the Agency requested access to the three locations on 2 May 2008. Analysis of satellite imagery taken of these locations indicates that landscaping activities and the removal of large containers took place shortly after the Agency’s request for access. While these activities may be unrelated to the Dair Alzour site, it would be helpful if Syria were to provide an explanation for these activities and to permit the Agency to visit the three locations.
Unfortunately, these three locations are mentioned only glancingly in GOV/2009/6. It doesn’t sound as if access has been granted, or will be anytime soon. And as for those “large containers,” what was in them and where they went is anybody’s guess.
Congratulations. You made it to the musical bonus.