Estimates vary of both the amount of plutonium in North Korea's possession and number of nuclear weapons that could be manufactured from the material. Official estimates of the amount of reproccessed plutonium reportedly range from 7 to 24 kilograms, and the amount of plutonium that North Korea would need for a single bomb range from 4 to 8 kilograms. Thus, by one calculation North Korea might have as many as six nuclear weapons, if it could use 24 kilograms to make 4 kilogram bombs. Or it might barely fall short of being able to make a single bomb, if it had only 7 kilograms when it needed 8 kilograms of plutonium.
South Korean, Japanese, and Russian intelligence estimates of the amount of plutonium separated, for example, are reported to be higher -- 7 to 22 kilograms, 16 to 24 kilograms, and 20 kilograms, respectively -- than the reported US estimate of about 12 kilograms. At least two of the estimates are said to be based on the assumption that North Korea removed fuel rods from the 5-MW(e) reactor and subsequently reprocessed the fuel during slowdowns in the reactor's operations in 1990 and 1991.
In principle the North Korea 5-MW(e) reactor would produce 0.9 gram of Plutonium per thermal megawatt every day of operations. When the yearly operations rate [capacity factor] is presumed to be 85 percent, the actual amount produced each year would be between 5.5 and 8.5 kilograms [given the range of estimates of between 20 and 30 megawatts thermal output. A lower, and possibly more realistic, estimate based on a capacity factor of 60 percent would suggest an annual production rate of between 4 and 6 kilograms.
In 1989, the reactor was shut down for a period variously estimated at between 70 and 100 days, and this would have provided enough time for North Korea to unload some or all of the fuel for reprocessing. By this time, the total production could have been somewhere between 8 and 15 kilograms of plutonium. North Korea claims that it only removed a few damaged fuel rods, which were reprocessed in the Radiochemical Laboratory in 1990. According to the North, these contained about 0.13 kilograms of plutonium, of which only a 0.09 kilograms were extracted.
When the reactor was shut down for refueling in April 1994, it was variously estimated that the unloaded spent fuel contained 17 to 33 kilograms of weapon-grade plutonium. The 8,000 spent fuel rods at the Yongbyon facility are in special canisters, under the watchful eye of the International Atomic Energy Agency 24 hours a day. Those eight thousand spent fuel rods contain enough plutonium for the North Koreans to build up to perhaps as many as six additional nuclear weapons. Absent international safeguards, North Korea could begin reprocessing the spent fuelinto plutonium for atomic bombs in six to eight months, according to some estimates.
The variations in the estimates about the number of weapons that could be produced from the material depend on a variety of factors, including assumptions about North Korea's reprocessing capabilities -- advanced technology yields more material -- and the amount of plutonium it takes to make a nuclear weapon. Until January 1994, the Department of Energy (DOE) estimated that 8 kilograms would be needed to make a small nuclear weapon. In January 1994, however, DOE reduced the estimate of the amount of plutonium needed to 4 kilograms.
On 22 April 1997, US Defense Department spokesman Kenneth Bacon officially stated, "When the US-North Korea nuclear agreement was signed in Geneva in 1994, the US intelligence authorities already believed North Korea had produced plutonium enough for at least one nuclear weapon." This was the first time the United States confirmed North Korea's possession of nuclear weapons.
According to a late 2002 CIA analysis, "Restarting the 5 megawatt reactor would generate about 6 kilograms [of plutonium] per year. ... The 50 megawatt-electric reactor at Yongbyon and the 200 megawatt-electric reactor at Taechon would generate about 275 kilograms per year, although it would take several years to complete construction of these reactors." If about 5 kilograms of plutonium was required for one bomb, the North Korean bomb-production rate would thus be about 55 weapons per year after the reactors are completed. ["North Korea Can Build Nukes Right Now," By Bill Gertz, The Washington Times, November 22, 2002 Pg. 1].
A story in the New York Times on July 20, 2003 reported that US intelligence officials believe that North Korea may have a second facility that could produce weapons-grade plutonium. The second facility is believed to be buried underground at an unknown location. The story, "North Korea Hides New Nuclear Site, Evidence Suggests" by David E. Sanger and Thom Shanker New York Times reported that sensors on North Korea's borders have begun to detect elevated levels of krypton-85, a gas emitted as spent fuel is converted into plutonium. The report says the issue that most concerns American and Asian officials, though, is analysis showing that the gas is not coming from North Korea's main nuclear plant, Yongbyon. Instead, the experts believe the gas may be coming from another hidden facility, buried deep in the mountains. North Korea is believed to have 11-15,000 underground military-industrial facilities.
The September 1, 2003 edition of Jane's Intelligence Review reports that the director of the the ROK's National Intelligence Service stated to the National Assembly in early July 2003 that North Korea had conducted 70 high-explosive tests at Yondok, 40km northwest of Yongbyon. Such high explosives could be used in plutonium device by compressing the plutonium core to create a nuclear explosion.
On 02 October 2003 North Korea said it had reprocessed eight thousand nuclear fuel rods and plutonium extracted from them could be used to strengthen its "nuclear deterrent force." A statement from the North Korean foreign ministry carried by the official Korean Central News Agency said that North Korea is manufacturing nuclear bombs with the material siphoned off from reprocessing eight thousand spent nuclear fuel rods. North Korea's latest claim came days after it warned it was taking "practical measures" to increase its nuclear deterrent against attacks by the United States. At the same time, a senior North Korean official reportedly said that his government will not export its nuclear capability. Vice Foreign Minister Choe Su Hon, said that Pyongyang does not intend to transfer its nuclear know-how to other countries.
During a visit to Yongbyon on 08 January 2004, North Korea showed an unofficial American delegation what it asserted was weapons-grade plutonium. The group spent about a day at Yongbyon, and was shown the empty cooling pond where the 8,000 fuel rods from the 5-megawatt nuclear reactor had been stored. During the visit, the reprocessing plant was operating.
In January 2004 DPRK Vice Minister of Foreign Affairs Kim Gye Gwan indicated that the DPRK had decided in November 2002 to operate the 5MWe reactor and resume reprocessing of plutonium for peaceful nuclear activities. He stated, "It is the only way to keep the spent fuel rods safe." He added, "At the same time, the hostile U.S. policy had been intensified. So, we changed our purpose and informed the U.S. that the plutonium that was to have been used for peaceful purposes would now be used for weapons. Originally, we had wanted to keep the reprocessed plutonium in a way we could store it safely. Then, we changed the purpose in order to strengthen our deterrent." During the 08 January 2004 visit of the American delegation, the North Koreans stated that they had initially intended to run the fuel cycle for civilian purposes, which means they would have stored the plutonium product as plutonium dioxide. Because of the "hostile U.S. actions" they reprocessed the entire campaign to plutonium metal. [Hecker testimony]
During the 08 January 2004 visit of the American delegation, the North Koreans stated that they reprocessed all 8000 spent fuel rods in the Radiochemical Laboratory in one continuous campaign, starting in mid-January 2003 and finishing by the end of June 2003. They stated that their capacity in the Radiochemical Laboratory is 375 kg uranium per day (they said they worked four 6-hr shifts around the clock). They later added that the reprocessing capacity of the facility under normal operating conditions is 110 tonnes of spent uranium fuel per year. Therefore, they were able to finish the current campaign of 50 tonnes of spent fuel rods in less than six months. They reprocessed the entire campaign to plutonium metal. They stated that this processing was done in the Radiochemical Laboratory by installing some glove boxes that were not present during IAEA inspections. It took them three months to install the equipment and prepare it for the plutonium metal processing step. These comments indicated that they had glove boxes for plutonium metal production ready to go in late 2002. This also indicated that they had experience making plutonium metal before the IAEA inspections began in 1992. The American delegation was shown the "product" from what the North Koreans claimed to be their most recent reprocessing campaign -- a wooden box with a glass jar they said contained 150 grams of plutonium oxalate powder and a glass jar they said contained 200 grams of plutonium metal for the Americans to inspect. [Hecker testimony]
US author and Korea expert Selig Harrison, completed a visit to Pyongyang in April 2005 that included talks with senior figures, including Kim Yong Nam, the country's second-ranking official. Harrison, of Washington's Center for International Policy, was reportedly told that North Korea would soon again harvest plutonium from fuel rods at its Yongbyon nuclear reactor, giving it enough nuclear explosive to build several more bombs.
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