Light Water Reactors and Nuclear Weapons in North Korea:
Let's Be Fair With Our Comparisons
By David Albright and Holly Higgins
October 27, 1999
On October 13, 1999, Congressman Christopher Cox (R-CA) said before a Hearing of the House International Relations Committee on "US Policy Towards North Korea:"
These light-water reactors will produce weapons-grade nuclear material. And in fact, according to the...Stockholm International Peace Research Institute [SIPRI], North Korea's light-water reactors...will accumulate plutonium and spent fuel at the rate of about 490 kilograms per year. That translates to about 100 bombs per year. Prior to the Agreed Framework...North Korea could produce from the other reactors about 12 bombs per year. So we are actually putting North Korea in a position to accumulate more material. The report [SIPRI] says, "After the LWRs start up, North Korea will accumulate plutonium in spent fuel at the rate of about 490 kg per year. Because this quantity is so large, North Korea will need to provide nuclear transparency to ensure that diversion does not occur." 1
We are flattered that Congressman Cox used information in our book, published by SIPRI and Oxford University Press. However, we wish he had used all the information in this chapter rather than just a small fraction of it. The message is quite different when all the information is considered. 2
- If the two light water reactors (LWRs) slated to be built in North Korea are operated to optimize power production, they will discharge about 500 kg of reactor-grade plutonium a year in highly radioactive spent fuel. However, this plutonium cannot be used in nuclear weapons until it is separated from this radioactive fuel. Typically, such separation occurs inside heavily shielded chemical processing plants, often called reprocessing plants. North Korea's existing reprocessing plant, which is shut down and under on-site IAEA monitoring under the freeze mandated in the Agreed Framework, would require extensive and difficult modification to separate all this plutonium. Alternatively, North Korea could build another one in secret, though such a step would violate the Agreed Framework, be difficult to accomplish, and the resulting plant would be relatively large. In fact, many advanced industrialized countries, such as Britain and France, experienced intensive challenges in making the jump to facilities that could reprocess irradiated fuel from LWRs, even after accumulating years of experience reprocessing irradiated fuel from gas-graphite reactors like those currently in North Korea.
- Separated reactor-grade plutonium can be used to make nuclear explosives, and typically eight kilograms are enough to make a crude nuclear explosive. Using this amount, the LWRs could produce enough plutonium for about 60 weapons per year, relatively close to the estimate cited by Rep. Cox. However, weapon designers prefer weapon-grade plutonium to make nuclear explosives. The two reactors at Yongbyon, and likely the third larger reactor at Taechon, were designed to make weapon-grade plutonium. If all three reactors were producing weapon-grade plutonium, and they would have all been capable of doing so by about 2000, then they could produce about 180-230 kilograms of weapon-grade plutonium per year. Because less weapon-grade plutonium is needed per nuclear weapon, this quantity is enough to make about 35-45 nuclear weapons a year.
- Clearly, the two LWRs can make more raw plutonium per year, but a more legitimate comparison is between roughly enough plutonium for 60 weapons per year in the case of the LWRs versus about 35-45 weapons per year in the case of the three gas-graphite reactors. Moreover, in about 2007, when the first LWR is expected to start, the gas-graphite reactors could have produced over 1,500 kilograms of weapon-grade plutonium, or enough for at least 300 nuclear weapons. By this time, North Korea would have had the largest stock of weapon-grade plutonium and nuclear weapons outside the five acknowledged nuclear weapon states, significantly larger than India's or Israel's present stock of weapon-grade plutonium.
- One way to reduce the amount of plutonium produced in the LWRs is to use a "high burnup" fueling strategy, which is increasingly used in LWRs worldwide. Insisting that North Korea irradiate its fuel to high burnups would significantly reduce the total quantity of plutonium discharged from the reactors each year and lead to even poorer quality plutonium that is harder to extract and use in the production of nuclear explosives or weapons.
Clandestine Plutonium Production
- According to Article XIII "Assurances" in the supply agreement under the Agreed Framework, North Korea agreed that the LWRs are exclusively for peaceful, non-explosive purposes. The agreement also states: "The DPRK shall at no time reprocess or increase the enrichment level of any nuclear material transferred pursuant to the Agreement, as well as any nuclear material used therein or produced through the use of such items, for the useful life of such reactors and nuclear material."
- North Korea does not have a suitable plant to separate plutonium produced in LWRs. Moreover, the construction of such a plant would violate the Agreed Framework. Building one large enough to separate the annual plutonium discharges from the LWRs would be difficult to build and easy to detect. North Korea could build a small, clandestine plant to reprocess LWR fuel, but again the diversion of a significant quantity of irradiated fuel from the LWRs would be straightforward to detect. If diversion was detected or suspected, the United States can insist that KEDO withdraw irradiated fuel from North Korea. Under Article VIII of the supply agreement, if KEDO requests, North Korea must relinquish ownership of the LWR spent fuel and transfer it out of the country as soon as technically possible after the fuel is discharged, through appropriate commercial contracts.
- Instead of reactor-grade plutonium, a LWR could produce significant quantities of weapon-grade plutonium. To do so on any large-scale, however, the reactors would need to be run at less than economically optimized levels. This is the type of activity that would be easy to detect. For example, IAEA safeguards, which North Korea must agree to before the reactors are even built, could easily detect such unusual reactor operations.
1 chapter 10, p.307, SIPRI report Plutonium and Highly Enriched Uranium 1996: World Inventories, Capabilities and Policies by D. Albright, F. Berkhout, W. Walker. Back to document
2 Only one of us (Albright) wrote that particular chapter of this book, so these comments reflect ISIS's views and not those of the other co-authors. Representative Cox also characterized SIPRI as a "leftist group." We cannot speak for SIPRI, which published our book, but the technical information in the book, such as the amount of plutonium produced and separated, is independent of political affinity. Back to document