北朝鮮の原子炉、活発に稼働・米シンクタンクが衛星写真

　【ソウル＝峯岸博】米シンクタンク「グローバル・セキュリティー」は15日までに北朝鮮・寧辺の実験用黒鉛減速炉（5000キロワット）が活発に稼働していることを確認できる衛星写真をホームページ上で公開した。

　写真は商業衛星で写真を提供している米デジタルグローブ社が今年1月と2003年当時などを比較する形で掲載した。同原子炉は核兵器に転用できるプルトニウムの製造が可能。今年1月の写真は原子炉関連施設の煙突から出る水蒸気の量が多くなっており、周辺道路の舗装が進んだことなども確認できる。

　北朝鮮は1994年の米朝枠組み合意により寧辺の原子炉の稼働を中断したが、2002年末に再稼働を表明。05年5月に「8000本の使用済み核燃料棒取り出しを終えた」と宣言した。 (13:47)

NIKKEI NET：主要ニュース

Yongbyon 5-MW(e) Reactor

The DPRK began constructing of a 5 megawatt (electrical) reactor in 1980, and US analysts reportedly believe that site preparation began in 1979. US satellite imagery reportedly detected site preparations and a nuclear reactor vessel under construction for the 5MW(e) reactor in April 1982. The reactor uses natural uranium for fuel -- which is readily available in North Korea -- and is believed to have become operational in the 1986-1987 timeframe.

Although this reactor is frequently termed a "5-MW(e)" research reactor, in fact it is thought to be capable of a thermal power output of between 20 and 30 megawatts. This is up to twice the thermal output that would normally be associated with a 5 megawatt electrical output [the electrical output is nominally one-third the thermal output].

The Yongbyon reactor is a gas-graphite reactor of some 25 MW thermal output which went into operation in 1986. The reactor has 801 channels for stacking fuel rods (10 fuel rods stuck in each channel) and for guiding control rods. Each fuel rod has diameter of 3cm and length of 50 cm. On an assumption that the 750 of these channels were occupied by fuel, the total fuel would be 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 is a routine procedure and DPRK's reply to IAEA later queries looked reasonable.

North Korea operated the reactor for approximately seven 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 create the technical possibility that fuel could have been removed and subsequently reprocessed. However, some US experts consider 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] 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 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 kg of plutonium with 239 isotopic composition around 90%. This would be an ideal weapons material when sufficiently cooled and reprocessed in the nearby Radio Chemical 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 eight 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 two inspectors to watch the fuel-removal process. 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 NPT. 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 03 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 5MWe reactor. North Korea reportedly estimates that the 5-megawatt reactor could be up and running in one to two months, while the IAEA reportedly believed it could take longer. As of 26 December 2002 the IAEA reportedly estimated that North Korea would have the five-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 continue to move fresh fuel rods into the Yongbyon reactor. The complex has a capacity of 8,000 fuel rods, and by 26 December 2002 the IAEA said 1,000 rods had been delivered. The North Koreans have told the agency they need one to two months to make the reactor operational.

On 27 February 2003, North Korea restarted the nuclear reactor at its Yongbyon facility.

During the 08 January 2004 visit of the American delegation, the North Koreans stated that they had removed all 8000 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 U.S. canisters had leaked during storage. But they 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. [Hecker testimony]

During the 08 January 2004 visit of the American delegation, 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 % of its rated thermal power. They claim 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) has been cut off. The North Koreans also stated that the length of time the reactor is expected to operate with the current 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 current fuel at any time. As of the time of the delegations visit, the reactor contained approximately 6 kg of plutonium in the spent fuel, and was assumed to continue to produce an additional 6 kg each year the reactor operates efficiently. [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. Having operated for about two 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 three 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 have verified that North Korea's Yongbyon nuclear power plant has been shut down. The plant may have been shut down to permit North Korea to remove spent plutonium and reprocess into weapons fuel.

Yongbyon 5-MW(e) Reactor

「北、寧辺原子炉を稼動中」証拠写真を公開

北朝鮮・平安北道寧辺（ピョンアンブクド・ニョンビョン）にある実験用黒鉛減速炉（５０００キロワット）が活発に稼働していることを示す衛星写真が公開された。

米シンクタンク「グローバルセキュリティー」は▽今年１月に５日に撮影した寧辺原子炉の衛星写真４枚▽０４年９月２９日と０３年３月５日、２０００年２月２２日にそれぞれ撮影した写真－－など計８枚を、最近ホームページ（www.globalsecurity.org/wmd/world/dprk/yongbyon-５.htm）上に公開した。今年１月と以前の状況を比較する形で掲載された。

今年１月の写真では、煙突から出される煙が鮮明に見える。北朝鮮が原子炉の稼働を中断していた２０００年２月の写真には、蒸気が見えない。煙突の蒸気は原子炉が活動中であることを示す。北朝鮮は９４年１０月、米国とジュネーブ枠組み合意に至った直後、寧辺原子炉を閉鎖したが、０３年２月２７日から原子炉を稼働している。

０４年４月１８日には、原子炉の稼働を再び中断したものと確認された。これは、原子炉の使い済み燃料棒から核兵器原料のプルトニウムを生産するためのもの、と見られた。１月の写真は、０４年にしばらくの間中断されていた原子炉が、再稼働中であることを示す。１月の写真では、周辺道路が舗装され、新たな施設も建設された様子が確認できる。

０４年９月の写真では舗装道路ではなかった。「グローバルセキュリティー」によると、北朝鮮は寧辺原子炉の燃料棒から、毎年、核爆弾１個を作れる量（少なくとも６キロ）のプルトニウムを生産できる、というのが韓米情報当局の判断。

李相逸（イ・サンイル）特派員


2006.05.15 13:37:01

Japanese JoongAngIlbo