North Korea’s Current and Future Plutonium and Nuclear Weapon Stocks

by David Albright

January 15, 2003

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Following North Korea’s announcement in December 2002 that it will restart several nuclear facilities at the Yongbyon nuclear research center, many questions have arisen about these facilities’ capabilities to make plutonium for nuclear weapons. The main facilities slated for restart are a 5 megawatt-electric gas-graphite reactor, a plutonium separation facility, and a fuel fabrication plant. All three facilities were shut down in 1994 under the US/North Korean Agreed Framework. Pictures of these facilities are available here.

Senior IAEA officials said in December 2002 that the reactor and plutonium separation plant could be restarted in 1-3 months. North Korea has maintained these facilities. For example, the last maintenance at the plutonium separation plant occurred in the summer of 2002. North Korea has not maintained the fuel fabrication plant, and it will need to undertake extensive renovation before this facility can operate. Before it was shut down in 1994, however, this plant is believed to have made enough fresh uranium fuel to reload the 5 megawatt-electric reactor and provide the initial core of the unfinished 50 megawatt-electric reactor.

In addition, North Korea announced that it was resuming construction of the larger gas-graphite reactors that had also been included in the “freeze” created by the Agreed Framework. These reactors include the 50 megawatt-electric reactor at Yongbyon and a 200 megawatt-electric reactor at Taechon.

The following discusses North Korea’s ability to produce and separate plutonium at these facilities in the format of questions and answers. This information is drawn mainly from the ISIS report Solving the North Korean Nuclear Puzzle.

1) How much separated plutonium does North Korea currently have? How many nuclear weapons may it possess?

The CIA, in an unclassified January 2003 report to Congress, wrote that North Korea “probably has produced enough plutonium for at least one, and possibly two, nuclear weapons.” Many have gone further than the CIA statement, claiming that North Korea definitely has enough plutonium for one or two nuclear weapons, although the basis for their claims is unclear.

The International Atomic Energy Agency (IAEA) determined in 1992 and 1993 that North Korea separated more plutonium than the roughly 100 grams it declared. The IAEA, however, was unable to determine how much more plutonium North Korea produced and separated. Based on these statements and other evidence discussed in Solving the North Korean Nuclear Puzzle, North Korea is likely to have hidden kilogram quantities of separated plutonium, but the exact amount of undeclared plutonium remains uncertain. The worst-case estimate is that North Korea separated about 7-11 kilograms of plutonium. Assuming five kilograms of plutonium per nuclear weapon, this is enough plutonium for one to two nuclear weapons.

2) Can North Korea make deliverable nuclear weapons?

In the early 1990s, many analysts doubted that North Korea was capable of building a deliverable nuclear weapon using separated plutonium. Given that North Korea is believed to have continued its work on building nuclear weapons after 1994, few maintain that North Korea is not now able to make deliverable nuclear weapons. ISIS has assessed that North Korea is likely capable of deploying nuclear warheads on its ballistic missiles that can reach Japan.

3) How much plutonium does North Korea have in the spent fuel discharged in 1994 from its 5 megawatt-electric reactor?

In 1994, North Korea discharged all the irradiated fuel in the 5 megawatt-electric reactor and moved it to a nearby spent fuel storage facility. In total, North Korea discharged about 8,000 fuel rods containing about 50 tonnes of uranium. Based on information from the IAEA, this spent fuel contained about 25-30 kilograms of plutonium. The average burnup of the fuel is about 650 megawatt-thermal-days per tonne of uranium fuel, implying the spent fuel contains about 27 kilograms of plutonium of which about 92 percent is plutonium 239. Assuming that a North Korean nuclear weapon requires about five kilograms of such plutonium, the spent fuel contains enough plutonium to make five nuclear weapons. Some of the fuel may be so damaged or corroded that it cannot be processed in the plutonium separation plant, but estimating this amount is difficult.

4) How quickly could North Korea separate a bomb’s worth of plutonium from the existing spent fuel produced in the 5 megawatt-electric reactor?

Senior IAEA officials estimated in December 2002 that North Korea could restart its plutonium separation plant, called the Radiochemical Laboratory, in 1-3 months. Indications are that North Korea has already launched an effort to restart this facility. This plant is a large facility with two processing lines. The first one, which operated successfully prior to the 1994 freeze, was capable at the time of separating about 11 tonnes of spent fuel in a single month of continuous operation. If a nuclear weapon needs five kilograms of plutonium, North Korea would need to process about 8.2 tonnes of its spent fuel. Starting at the first of the year and allowing one month for restart and less than a month for processing the spent fuel, North Korea could separate enough plutonium for a nuclear weapon by March 2003.

5) How long would North Korea need to separate all the plutonium in the existing spent fuel?

Based on the above, North Korea could extract all the plutonium in its spent fuel in about six months. This estimate assumes some delays in processing all the spent fuel. If the restart of the plant takes three months and processing delays are substantial, North Korea may need nine months to process all of its spent fuel.

6) How long would North Korea need to produce enough plutonium for a nuclear weapon in the 5 megawatt-electric reactor at Yongbyon?

North Korea may have already reloaded fuel into the reactor and may restart this reactor by February 2003. However, this reactor contains a relatively large amount of fuel and produces little power. As a result, irradiation of the fuel, and the production of plutonium, occurs relatively slowly. If the reactor operated continuously for one year at five megawatts-electric, or 20 megawatts-thermal, it would produce about 7.4 kilograms of plutonium in the fuel. This level of irradiation corresponds to a low burnup of about 150 megawatt-thermal-days per tonne of uranium fuel. After two years of continuous operation, the reactor could produce about 15 kilograms of plutonium in fuel with a burnup of about 290 megawatt-thermal-days per tonne, or enough for three nuclear weapons. After discharge from the reactor, the spent fuel would need to be cooled in the storage pond for a few months before the fuel could be processed in the Radiochemical Laboratory. Processing this spent fuel would take about five months, assuming that only one processing line operates.

7) How long would North Korea need to finish the 50 megawatt-electric reactor at Yongbyon? Once finished, how much plutonium could this reactor produce each year? How many nuclear weapons?

In 1994, this reactor was about two years from completion. North Korea could still probably finish in this amount of time. Operating at design values, the 50 megawatt-electric reactor would produce about 55 kilograms of plutonium each year, or enough for eleven nuclear weapons per year.

8) How long would North Korea need to finish the 200 megawatt-electric reactor at Taechon? Once finished, how much plutonium could this reactor produce each year? How many nuclear weapons?

In 1994, this reactor was estimated to be still more than two years from completion. North Korea is unlikely to finish this reactor for several years. If this reactor were operated to produce plutonium for weapons, it could produce an estimated 220 kilograms of plutonium per year, or enough plutonium for 44 nuclear weapons per year.

9) How much plutonium could all three gas-graphite reactors produce annually when operating at design values? How many weapons?

All three reactors could produce about 280 kilograms of plutonium per year, or enough for about 56 nuclear weapons per year. North Korea would need several years to reach this level of production.

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