5 MW(e) Reactor
The DPRK began constructing of a 5 Megawatt (Electrical) (5-MW(e)) reactor in 1980, and US analysts reportedly believed that site preparation began in 1979. US satellite imagery reportedly detected site preparations and a nuclear reactor vessel under construction for the 5-MW(e) reactor in April 1982. The reactor used natural uranium for fuel, which was readily available in North Korea, and was believed to have become operational in the 1986-1987 timeframe.
Although this reactor Was frequently termed a "5-MW(e)" research reactor, in fact it was thought to be capable of a thermal power output of between 20 and 30 megawatts. This was up to twice the thermal output that would normally be associated with a 5 megawatt electrical output. The electrical output was nominally one-third the thermal output.
The Yongbyon reactor was a gas-graphite reactor of some 25 MW thermal output, which went into operation in 1986. The reactor had 801 channels for stacking fuel rods (10 fuel rods stuck in each channel) and for guiding control rods. Each fuel rod had a diameter of 3 cm and length of 50 cm. On an assumption that the 750 of these channels were occupied by fuel, the total fuel would have been around 45 tons.
The DPRK had reported to IAEA that 86 fuel rods had been removed from the reactor in 1989 for post irradiation examination to check fuel integrity and to check computer calculation of neutron flux. This was a routine procedure and DPRK's reply to IAEA later queries looked reasonable.
North Korea operated the reactor for approximately 7 years. This plutonium production reactor became operational in 1986, and probably began operating at full-power by October 1987, with some refueling in 1989. North Korea shut down the 5-MW(e) reactor for between 70 to 100 days in 1989. Some sources believe that North Korea removed and later reprocessed the fuel, separating up to 13 kilograms of weapons-grade plutonium usable for producing nuclear bombs. The suspected diversion was, among other things, inferred from a subsequent laboratory analysis of materials collected during IAEA's inspections that began in 1992.
North Korea ran the 5-MW(e) reactor at low levels for about 30 days in 1990 and about 50 days in 1991. Such low levels of operation created the technical possibility that fuel could have been removed and subsequently reprocessed. However, some US experts considered this unlikely. Fuel from this reactor also was discharged in May-June 1994 and, had it been reprocessed, could have provided enough plutonium for several additional nuclear weapons.
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) was 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 claimed 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 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 40 kilograms of weapon-grade plutonium. By 1994 when the full core was discharged, the level of irradiation must have been around 900 WMD/T containing as much as 40 kilograms of plutonium with 239 isotopic composition around 90 percent. This would be an ideal weapons material when sufficiently cooled and reprocessed in the nearby Radiochemical Laboratory.
In early 1994, the DPRK informed the IAEA that it intended to refuel the 5 MW Experimental Nuclear Power Reactor, loaded in 1986 and operated since 1987. The IAEA wished during such refuelling to select a number of fuel rods, segregate them from the others, secure them so that they would not be replaced by others and examine them. This was requested because an examination of the rods might show how long they had been in the reactor. If it were found that some or all the rods in the reactor had been there for a shorter time than 8 years, then there could exist non-declared nuclear material, spent fuel, or perhaps plutonium and waste.
In Mid-May 1994, workers began removing the spent fuel from the 5-MW(e) reactor in violation of North Korea's safeguards agreement with IAEA and IAEA's previous instructions informing North Korea that IAEA inspectors would need to sample, segregate, and monitor the fuel rods to preserve evidence of past plutonium production. North Korea refused to comply, but allowed 2 inspectors to watch the fuel-removal process. The IAEA informed North Korea that the removal of fuel without proper safeguards constituted "a serious violation" of the safeguards agreement.
The United States offered to hold the long-deferred third series of high-level talks to consider the entire range of issues related to the Korean peninsula, including the economic, diplomatic, and other benefits that North Korea could receive in return for reversing its decision to withdraw from the Non-Proliferation Treaty. The talks were conditioned on North Korea's willingness to allow IAEA to monitor the refueling operation and to safeguard the fuel rods already removed.
On 3 June 1994, IAEA's Director General told the United Nations Security Council that North Korea had removed all but 1,800 of the 8,000 fuel rods in the 5-MW(e) reactor and that by mixing them up, North Korea had made it impossible to reconstruct the operating history of the reactor.
On or about 24 December 2002, North Korea moved fresh fuel to the 5-MWe reactor. North Korea reportedly estimated that the 5-megawatt reactor could be up and running in 1-2 months, while the IAEA reportedly believed it would take longer. As of 26 December 2002, the IAEA reportedly estimated that North Korea would have the 5-megawatt reactor operational by the end of February 2003. A senior South Korean official concurred with that estimate. "We believe it will take one or two months to restart the reactor," said the official, Chun Young Woo, director general for international institutions at the Foreign Ministry. The North Koreans continued to move fresh fuel rods into the Yongbyon reactor. The complex had a capacity of 8,000 fuel rods, and by 26 December 2002 the IAEA said 1,000 rods had been delivered. The North Koreans had told the agency they needed 1-2 months to make the reactor operational.
On 27 February 2003, North Korea restarted the nuclear reactor at its Yongbyon facility.
On 8 January 2004, an unofficial American delegation led by Siegfried Heckler visited North Korea and the Yongbyon complex. The North Koreans stated to the degelation that they had removed all 8,000 fuel rods from the spent fuel storage pool and shipped them to the Radiochemical Laboratory (the plutonium reprocessing facility) and reprocessed them to extract the plutonium. The fuel rods were taken out of the pool in Korean containers (metal baskets) and placed in specially shielded shipping casks. During the removal of the fuel rods they found that about half of the US canisters had leaked during storage. The North Koreans claimed not to have experienced major problems getting the spent fuel rods out of the pool and transporting them in special casks by truck daily to the Radiochemical Laboratory for reprocessing.
Also during the 08 January 2004 visit, the North Koreans stated that they had restarted only the Experimental Nuclear Power Plant (the 5 MWe reactor). The plant was restarted in February 2003. The North Koreans stated that it was operating smoothly at 100 percent of its rated thermal power. They claimed to be producing electricity and heat from the reactor now for their town. The reactor was said to be the main source of heat for the town now that the 10,000 metric tons (tonnes) of heavy fuel oil supplied annually to their region (as part of the 500,000 tonnes agreed to in the Agreed Framework) had been cut off. The North Koreans also stated that the length of time the reactor is expected to operate with the existing load of fuel depended on how the situation with the United States developed. They claimed not to have safety concerns about running the reactor for a long time (implying years). They stated that some of the operational problems experienced previously had been corrected. However, they said they were prepared to reprocess the fuel at any time. As of the time of the delegations visit, the reactor contained approximately 6 kilograms of plutonium in the spent fuel, and was assumed to continue to produce an additional 6 kilograms each year the reactor operated efficiently.
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. Having operated for about 2 years, assuming a capacity factor of 60 percent would suggest a total production of between 8 and 12 kilograms, certainly enough for at least one bomb and possibly as many as 3 bombs.
By 18 April 2004, it appeared that North Korea had shut down the reactor, in a possible prelude to reprocessing spent fuel rods into weapons material. A South Korean Foreign Ministry official told local media that his government and the United States had verified that North Korea's Yongbyon nuclear power plant had been shut down. The plant may have been shut down to permit North Korea to remove spent plutonium and reprocess into weapons fuel.
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