Jeffrey LewisIts All About (Water) Chemistry

I’ve noticed some confusion among folks about the disablement process in North Korea — let’s make this very, very clear. All of the disablement steps are believed completed save for the unloading of fuel, which was delayed by the need to ready the cooling pond to receive the spent fuel and is on schedule to be completed in 100 days.

AS Hill himself stated that the “some of the things that held us up in disablement had nothing to do with any negotiation elements; rather, it was a safety and technical issue.” Andreas Persbo — who represents a pretty informed outside observer — expressed some difficulty in imagining what those problems might be.

Sig Hecker (right), in a talk hosted by the Los Alamos Committee on Arms Control and International Security, explained that the issue was fixing the water treatment plant in order to correct the water chemistry in cooling pond. (This was completed, I think, on December 14; North Korea began unloading the fuel the next day or so.)

Water chemistry is essential to avoiding corrosion of the fuel rods while they are stored. One wants the right Ph level, and not too many minerals such as chlorides and sulfates, to prevent the fuel rods from corroding. For MAGNOX fuel, one wants a ph level about 11.5 and less than 1 ppm chlorides and 4 ppm sulphates to store the fuel for up to five years. (A nice mineral water, while it might taste good, would be a terrible choice for a cooling pond.)

If you want the details, the IAEA published a nice little primer, Further Analysis of Extended Storage of Spent Fuel, IAEATECDOC-944, IAEA, Vienna, 1997, see especially page 17.

The North Koreans, who planned to reprocess the fuel and were not concerned about long-term storage, just used regular water. The results, as David Albright explained back in 1994, were pretty ugly:

The current conditions in the spent fuel ponds do not bode well for long term storage. The North has implemented little Western technology to slow corrosion of the cladding.


The actual rate of corrosion of the fuel in the ponds is unknown. The IAEA has reported that, based on its inspectors’ observations, the water is opaque and dirty, and the ponds do not have adequate filtering or purification systems. A video of North Korean nuclear facilities made public by the IAEA in 1992 shows the spent fuel ponds green with algae.

More important, the IAEA has said that the North does not conduct detailed water chemistry analyses of the water in its ponds. It also does not control the level of certain impurities that can greatly accelerate cladding corrosion, particularly chlorides and sulfates.

Apparently, things hadn’t gotten any better in the intervening 13 years.


  1. PC (History)

    It seemed to me that Chris Hill was trying to prepare for a disablement process that was going to go beyond Dec 31 as early as the beginning of November:

    According to U.S. officials, a fairly urgent part of the process will involve cleaning the storage pond where spent fuel rods from the reactor are left to cool prior to reprocessing. The pond is currently filled with radioactive debris and poses a health hazard to anyone working on disablement at the site. Hill said Nov. 3 that the cleaning process will take “a lot longer” than a couple of weeks…Hill, however, seemed to leave room for the possibility that the disablement process will continue into early next year. Citing the need to proceed cautiously due to safety reasons, he told reporters Nov. 3 that “even at the end of December, when we will have substantial disabling, we need to be careful not to hurry things in a way that could cause any health risk to anyone working on the process.”

    As for the filtration system, according to Ken Quinnones, who had an excellent piece last November comparing Agreed Framework to disablement, said that the filtration system was replaced in 95 with a U.S. one:

    Disablement was unnecessary in 1994 because North Korea’s nuclear facilities had already become disabled. The primary task for American technicians became the cleaning of the water in the spent fuel pond so that the spent fuel could be located, cleaned and “canned” for long-term storage. To begin this process, the American contractor Centec 21 of San Jose, California designed and installed in the summer of 1995 a new, modern U.S.-designed water filtration system.

    I don’t know whether that has made a lick of a difference at this point though….

  2. Rwendland (History)

    I hope there is a firm plan for what to do with this final fuel load within the 2 to 5 years maximum Magnox fuel can be left in a well conditioned cooling pond. The UK’s contingency plan for its final two Magnox reactors, if its reprocessing capacity for Magnox fuel is inadequate, is actually to leave the fuel in the shutdown reactor for a while. A shutdown reactor is actually a pretty good dry-store for spent Magnox fuel. Once it is dunked in the water the clock is ticking on disposing it. I’m worried that political demands are pushing us forward too fast, before we have the complete fuel disposal plan in place.

    I’m not sure we can expect the maximum 5 years storage at Yongbyon. I think the UK 5 year storage involves containerisation of the fuel with a good initial water chemistry, and perhaps pool chilling. The Yongbyon pool has I suspect open storage in racks underwater, so unless another approach has been developed in the last few months, a maximum 2 years storage may well be a more reasonable expectation.

    Exporting the spent fuel will be difficult. I’d have thought by far the best technical solution would be to let the North Koreans reprocess this last fuel load, and export the product – but sadly I suspect this is politically impossible for the U.S.

    Not sure which other reprocessing plants could tackle this Magnox/uranium metal fuel job. The rail links to China or Russia might be the easiest route out for unreprocessed spent fuel. UK’s Magnox fuel reprocessing plant is planned to be closed in 2012 (could slip to 2016), so little time to spare if we want to use that.

  3. Jeffrey Lewis (History)

    A canning operation is anticipated.

  4. Rwendland (History)

    I wonder if the North Koreans will, quite rationally, refuse to fully disable the reprocessing plant before the spent fuel is removed or they are convinced a fully-funded definite plan for the fuel is in place. There is the risk that this will then be presented in the West as the North Koreans being obstructive, when they may well be genuinely concerned just to ensure they have a way to safely get rid of an especially difficult to keep spent fuel.

    I’m not sure enough people appreciate that Magnox fuel (Uranium metal in Magnesium alloy sheath – both water reactive, but with an excellent neutron economy) is quite unlike spent PWR fuel (ceramic pellets of enriched uranium dioxide in corrosion-resistant zirconium alloy). It was originally designed to be reprocessed 4-12 months after use. It would be good if this is explained to journalists.

  5. Jeffrey Lewis (History)

    Dear Richard:

    The disablement steps for the reprocessing facility — the two steps I know are disconnecting the drive mechanism between the spent fuel receiving building and the hot cell and removing the steam lines — are already completed.

    (I am not sure if those steps are different from “Remove drive mechanism for fuel cask transfers” and “Removal of mechanism for fuel” which are captions on <a href=“”>photographs</a&#062; floating around.)

    At this point, North Korea would have to repair those systems to reprocess the fuel.

    I agree that journalists should understand this technical fact of how difficult it is to store MAGNOX fuel rods, but there are only a handful of technically literate journalists like Mark Hibbs.

  6. PC (History)

    According to the DOE, the disablement process is pretty much funded and good to go—up to canning and removing the SF. The NDF funds they are using so far are basically dried up by then, and they need legal authority to use DOE funds for additional work. There seem to be hopes that someone else will chip in and fund this process and take the fuel themselves—-maybe as a Global Partnership effort or something like that.

  7. Eli (History)

    Is the funding you are discussing include the $10 million that was given to the NNSA in the December Omnibus bill, directly for the purpose of North Korean disablement efforts?
    The related section states as well that the Energy and Water Committee strongly supports the funding of disablement and are worried not enough money/flexibility existed before the Omnibus became law. They even offered to support a supplemental if further funding became necessary. Relevant sections can be found here:

    On a different note, I was wondering why we have seen little discussion over the importance of taking steps to verify North Korea’s claim of 30kg separated Pu stocks? ISIS published a quick article,,
    that made some important points about how the US’ focus on the Uranium question has kept us from pursuing important verification steps concerning the history of their reprocessing efforts. I’m certainly all for pushing for a complete declaration, but if the North Koreans are willing to offer up information on the most dangerous and critical part of their nuclear program, why are we letting anything get in our way?