James ActonA Lot of NORK Pu

Glenn Kessler reported in the Washington Post yesterday that the US Intelligence Community has revised its estimate of the amount of plutonium separated at Yongbyon.

U.S. intelligence analysts have prepared a fresh estimate of the size of North Korea’s stockpile of plutonium—larger than previous assessments—that will be compared with the information contained in 18,822 pages of reactor production records turned over by North Korea last week, according to U.S. officials.

North Korean officials have said about 30 kilograms of plutonium was produced at their five-megawatt reactor at Yongbyon, at the low end of most private and government estimates. The new U.S. estimate is expected to be from 35 to 40 or 50 to 60 kilograms, though sources would not detail how much it had increased from the last government estimate.

The US estimate is divided into two blocks: either 35—40 kg or 50—60 kg but not in between. The reason for the two blocks, as it says later in the article, is presumably uncertainty about whether the reactor was used and unloaded prior to 1990. I’m also assuming (although it’s not 100% clear) that these figures refer to separated plutonium (not the total amount of unseparated Pu present in the fuel at the time of unloading).

The 35—40 kg part comes from the fuel which was unloaded in 1994 and 2005 and subsequently reprocessed. This lies within the ISIS estimate of 33—45 kg.

The 50—60 kg part of the estimate is more interesting. We know that none of the plutonium from the current unloading has been separated so the US IC must be assuming that if the North Koreans used their reactor before 1990, they produced 15—20 kg of plutonium.

This is a lot; much more than the 1—10 kg figure given by Albright. (All of this neglects the Pu that may have been extracted from the IRT reactor but that’s only a kg or two at most.)

This is also odd. The US IC seems to be uncertain about whether the reactor operated at all before 1990, yet is certain that if it did operate it produced at least 15 kg of plutonium.

One other observation: The North Korean 30 kg apparently excludes the material used in the test, whereas the US figures don’t—so it is just possible they are consistent.

In any event, the verification is going to be interesting.


  1. Glenn Kessler (History)

    I am always pleased when my articles are mentioned on ACW, but I want to point out that an unfortunate bit of copy editing changed the wording of a key sentence, making it very confusing. (And unfortunately, I did not see this change until I opened the newspaper in the morning.) The sentence, AS IT APPEARED IN THE NEWSPAPER, was: “The new U.S. estimate is expected to be from 35 to 40 or 50 to 60 kilograms.” BUT THIS IS HOW IT SHOULD HAVE READ: “The new U.S. estimate is expected to be between 35-40 and 50-60 kilograms.” In other words, there are not two blocks, but a single range that will be between 35 and 60 kilograms. My sources were vague on the exact numbers at the upper and lower part of the range, which is why it was written like that. I think it is more likely to be in the upper range—ie, 40-60 kilograms. Two sources said that it had been 30-50, but the CIA increased it by ten kg, to 40-60. But a senior official cautioned me on using a precise 10 kg figure, so I did not use it in the article. I hope this clarifies this crucial point, and I apologize if anyone was misled by the language that appeared in the newspaper.

  2. peter Zimmerman (History)

    It’s a good bet that the reactor operated before 1990, but not a certainty. There was much uncertainty within the Clinton Administration as to how many reprocessing campaigns had been undertaken, and I think this uncertainty still persists.

    The probable reason for the 15-20 kg estimate on pre-1990 operation is the capacity of the reactor and the ‘economics’ of when to refuel. The North Koreans haven’t made this simple. You’ll remember that when they off-loaded in the mid-90s they carefully scrambled the fuel pins and bundles so that it was impossible, or at least very difficult, to reconstruct the reactor’s real history.

    I have enormous respect for David Albright, but he wasn’t there when the reactor was running, and his analysis isn’t definitive. The DPRK records should help clear things up, as should a thorough study of the reactor, fuel storage area(s) and the hot cells of the reprocessing plant itself.

    What I cannot tell from the news and my sources around town is how much of the “separated plutonium” is still stuck in pipes and reaction cells and otherwise in the MUF category.

  3. Paul Carroll (History)

    Getting an accurate accounting of the plutonium produced and, as you point out, especially the separated plutonium is a critical part of the Six Party agreement and U.S. satisfaction on this is pivotal to moving forward on the other aspects of the deal. What will be important to keep in mind, though, is when to be “satisfied” and what quantities might be acceptable to chalk up to accounting and/or “held up in pipes” amounts. Don’t forget that our own weapons complex and labs have been reviewed and shown to be wanting for tens and even hundreds of kilograms of plutonium. Is this “real” plutonium or just a paper error? Obviously, when dealing with North Korea and the risk of diversion or concealment we want the uncertainty to be as low as possible. But I would urge us to caution against demanding levels of certainty that may be unattainable, and that could undermine progress on the other aspects of the deal.