How Japan Lost Track of 640kg of Plutonium

Lasrick sends this quote from the Bulletin of the Atomic Scientists: Most people would agree that keeping track of dangerous material is generally a good idea. So it may come as a surprise to some that the arrangements that are supposed to account for weapon-grade fissile materials—plutonium and highly enriched uranium—are sketchy at best. The most recent example involves several hundreds kilograms of plutonium that appear to have fallen through the cracks in various reporting arrangements. ... [A Japanese researcher discovered] that the public record of Japan’s plutonium holdings failed to account for about 640 kilograms of the material. The error made its way to the annual plutonium management report that Japan voluntarily submits to the International Atomic Energy Agency ... This episode may have been a simple clerical error, but it was yet another reminder of the troubling fact that we know very little about the amounts of fissile material that are circulating around the globe. The only reason the discrepancy was discovered in this case was the fact that Japan has been unusually transparent about its plutonium stocks. ... No other country does this.

Misreporting

[Anonymous Coward]

From TFA: "No plutonium was actually lost, ... the material ended up in the wrong column on a spreadsheet."

That's because all Pu isn't created equal. It begins as some Pu in a used fuel element. It can be separated to become elemental Pu, which is somewhat dificult. The Japanese incorporate this into MOX fuel, from which it could easily be separated again (which would be pointless, but never mind). And then the MOX fuel is used, and the Pu (both old and new) becomes difficult to isolate again. This particular 640kg of Pu is in the form of an unused MOX core for a reactor which was scheduled to be started, but due to the hasty shutdown of all nuclear power in Japan after March 2011 never was. So the Pu in the unused core ended up in the books as a used MOX core.

Moreover, Podvig hints that this is about weapons grade material. It's not. Japan doesn't have a (working) fast breeder, no Hanford-style Pu production reactor, and no Magnox-style dual purpose reactors. This Pu is from light water reactors, therefore heavily irradiated, therefore isotopically a mess, and therefore not weapons-grade and never going to be weapons grade by any means. But Podvig makes a living off the case of nuclear non-proliferation, so of course desaster is looming, or he wouldn't have a job anymore.

Re:Come now.

[taiwanjohn]

According to another post [slashdot.org] this plutonium could not be used to make a bomb, and the explanation makes sense to me. So even if they change the constitution they won't be making any bombs, at least not with this plutonium.

Re:Come now.

[MachineShedFred]

Except that "reactor grade" plutonium is unsuitable for weapons, and cannot have the undesired isotopes of plutonium separated out of it to make it weapons grade. There's a reason why the US built the special reactors at Hanford for weapons production - you can't just make material suitable for weapons in any commercial generating station.

But besides that, yeah we should all duck and cover.

Re:Come now.

[Mr D from 63]

Except that it was never lost, and you'll find that not in the summary, but midway through TFA where it says they just entered it in the wrong column on a spreadsheet . Disaster averted. Spreadsheets are actually tools of terror!

Why I vote Republican

[Anonymous Coward]

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Re:Well dang, 640 kg?

[Anonymous Coward]

1) It wasn't 640kg of plutonium. It was 640kg of fuel rods that contains a much smaller amount of plutonium
2) They were at Fukushima the whole time.
3) The "Dude, Where's My Plutonium?" spreadsheet didn't have a column for "Halfway loaded into a reactor that just got hit by a tsunami"
4) The plutonium bean counters noticed that SUM() didn't include the new column.