When the US-DPRK Geneva Agreed Framework was signed in October 1994, it appeared that the North Korean nuclear breakout had been turned around. But the second North Korean nuclear crisis in 2002—triggered over Pyongyang's allegedly illicit program of producing highly enriched uranium—not only shattered the Agreed Framework. The issue now threatens to spiral out of control. The Six-Party Talks—involving North and South Korea, the United States, China, Japan, and Russia—have stalled and Pyongyang has conducted three underground nuclear tests. Claiming that it has been successful in diversifying as well as miniaturizing both plutonium and uranium bombs, North Korea (officially the Democratic People's Republic of Korea) on February 12, 2013, publicly proclaimed that it has become the ninth nuclear-weapon state. The North Korean nuclear threat is no longer hypothetical, but real and present.

For now, South Korea (officially the Republic of Korea) still favors a peaceful settlement through dialogue and negotiations, especially the Six-Party Talks. But some South Korean conservatives are growing increasingly impatient. They argue that the United States should redeploy tactical nuclear weapons in the South, or that the South should develop its own nuclear weapons. This sentiment has been fueled by a recent debate in the United States as to whether it should reject or accommodate such a move, as well as by the prospect that North Korea eventually will develop the ability to hit the United States with a few nuclear weapons.        

Against this backdrop, the paper examines the dynamics of the nuclear threat in Korea and explores options for reducing the role of nuclear weapons in regional security. The first section of the essay traces the history of North Korea’s nuclear weapons and analyzes its nuclear capabilities and motives. It also addresses the peninsular, regional, and global security implications of this nuclear breakout. The second section examines South Korea's response, especially focusing on recent debates about the United States reintroducing tactical nuclear weapons or the South developing its own nuclear weapons capability. The third section presents the option of developing a comprehensive security settlement and creating a Northeast Asian nuclear weapon-free zone as a way out of the Korean nuclear quagmire. Finally, we draw some policy implications about how to deal with the peninsular nuclear problems in the context of a revived global effort to abolish nuclear weapons.

Like the South, North Korea initiated a nuclear program in the 1950s and 1960s. In 1965, it operated a tiny IRT-2000 research reactor with the help of the former Soviet Union.

The precise date when North Korea decided to pursue and develop nuclear weapons is not known. Kim Il Sung likely began thinking about nuclear weapons as a result of the Korean War, at which time American nuclear threats were aimed explicitly at China and the North Korean military. The United States deployed nuclear weapons in Korea in 1958. During the 1960s the former Soviet Union and its Eastern European allies consistently rebuffed North Korean requests for nuclear technology, perhaps worrying that any technology they provided the North would find its way to China. Some speculate that the North was matching South Korea’s nuclear weapons program that began in 1971.

In April 1975, North Korean leader Kim Il Sung visited China and asked Mao Tse-tung for off-the-shelf nuclear weapons to allow him to take advantage of demonstrations in South Korea against President Park Chung-hee. Kim’s intention was to ride the revolutionary wave created by the fall of Saigon in South Vietnam and Phnom Penh in Cambodia and foment a popular revolution in the South. At that time, North Korea was at the apogee of its power and Kim Il Sung wanted nuclear weapons to limit US intervention if war broke out on the peninsula. There are also some scholars who believe that an active North Korean nuclear weapons program was triggered by the August 1976 crisis in which the United States deployed ground-based tactical nuclear weapons as part of its response to the killing of two American officers at Panmunjom in the Korean Demilitarized Zone.

In any event, it is clear that by the mid-1980s, North Korea had begun to realign its nuclear program to produce weapons. In the late 1980s, the Department of Defense Industry of the Korea Workers' Party took over the management of nuclear facilities in Yongbyon. In 1986, the North began to build a five-megawatt graphite-moderated reactor that was able to produce plutonium and a “radioactive chemical lab” (that is, a reprocessing facility). Although the 1994 Geneva Agreed Framework froze nuclear facilities and activities in Yongbyon, the North tested the high explosives needed for detonating a nuclear weapon between 1993 and 1998 in the nearby mountains.

After the Agreed Framework fell apart in the wake of the second nuclear crisis in 2002, Pyongyang reactivated its five-megawatt nuclear reactor in Yongbyon and began to extract plutonium. As the Six-Party Talks stalled, the North tested nuclear weapons in October 2006, May 2009, and February 2013. North Korea referred to its nuclear weapons in discussions with American officials in 2003 and made many public references to its nuclear weapons between 2003 and 2010, when its foreign affairs ministry declared on May 26 that it was satisfied to be a nuclear-armed state (as against a nuclear-weapon state recognized as legitimate by the Nuclear Non-Proliferation Treaty [NPT], from which it had earlier departed). “The DPRK,” averred the spokesman, "is just satisfied with the pride and self-esteem that it is capable of reliably defending the sovereignty of the country and the security of the nation with its own nuclear weapons.”

However, for a state to be recognized as effectively capable of detonating a nuclear warhead against a target—that is, to be nuclear-armed—it must not only blow up a nuclear device, but must meet four conditions: possession of nuclear warheads, demonstration of delivery capability, nuclear testing, and miniaturization of nuclear warheads to mount on missiles. We will examine each of these necessary conditions.

The first question is how much fissile material for nuclear weapons North Korea possesses. Until recently, most of the discussion has centered on how much plutonium was obtained from spent fuel at the Yongbyon graphite-cooled reactor frozen by the 1994 Agreed Framework. Estimates vary, but the North’s reprocessing campaigns from this reactor’s spent fuel might have yielded as many as five bombs-worth of plutonium. (The exact amount depends on the warhead design as well as the burn-up of the fuel in the reactor and the efficiency of the reprocessing, and is possibly substantially less than five.) Reactivation of this reactor (which as of December 2014 was in progress but not complete) might produce an estimated six to seven kilograms of plutonium or about one warhead-per-year equivalent. When completed and operating, North Korea's new twenty-five-megawatt light-water reactor might yield about fifty-six kilograms of plutonium per year, enough to manufacture up to eleven bombs per year. In mid-2012, its plutonium inventory was estimated to be capped with enough for six to eighteen weapons-worth, and a midpoint of twelve weapons-worth, reduced by 2014 by one weapons-worth of plutonium used in the 2013 test. (These estimates might vary upward slightly if the North mastered small warheads using less fissile material very early in its development efforts.)

To the plutonium inventory we must add material produced by North Korea's highly enriched uranium (HEU) program. In this regard, the most serious uncertainty is whether it operated a clandestine enrichment plant and, if so, what size and for how long. There is also the question of the HEU production at the Yongbyon enrichment plant shown to Stanford University scholar Siegfried Hecker in 2010. One estimate, based on detailed open-source information, comparable programs in other states, and highly informed technical analysis of plutonium and enrichment technology, is that as of mid-2012, North Korea had between zero and twelve nuclear weapons-worth of highly enriched uranium (each assumed to contain twenty kilograms of weapons-grade HEU). By 2014, this 2012 range for the total inventory of highly enriched uranium might have increased at most by ten weapons-worth, depending on the number of centrifuges in operation, the plant operating factor, whether the North made low-enriched fuel for its small light-water reactor between 2012 and 2014, and the level of enrichment used for the weapon. Roughly, therefore, by 2014 North Korea could have had as few as five weapons-worth of plutonium and zero weapons-worth of highly enriched uranium, or as much as seventeen weapons-worth of plutonium plus, at most, ten weapons-worth of highly enriched uranium.

Delivering nuclear weapons, the second aspect of a nuclear weapons capability, is another matter altogether. North Korea has proved that it has credible short- and middle-range delivery capability including KN-02, Scud B and C, Nodong, and Musudan missiles. These missiles are known to be unreliable and inaccurate. But if it were firing nuclear weapons in an all-out attack on South Korean cities, this might not matter too much—although the plausibility of such a suicidal spasm is dubious. The five test-launchings of intercontinental range Daepodong-I missiles (1998) and Daepodong-II missiles (2006, 2009, and 2012) all failed. But the most recent launching of space launch rocket Eunha 3 with a dual-use application to long range missiles, on December 12, 2012, succeeded. The rocket put a small satellite into orbit, although North Korea was unable to communicate with or control it. Thus, Pyongyang does have some missile delivery capability—enough to cause considerable damage to South Korea, possibly to Japan, and, speculatively, even to the United States. Some analysts also argue that the North might use submarines, fishing trawlers, tunnels, or even foreign-flagged merchant vessels to deliver nuclear weapons outside its border. However, such means of delivery would require pre-delegated use authority along with small and reliable warheads, and would risk discovery and subsequent great power intervention. Therefore, we believe such attacks are implausible.

The third prerequisite is well-tested nuclear warheads. Although its first test was likely a dud, its second and third tests had yields of two to six kilotons and seven and a half kilotons, respectively. It is still not known if the third test used uranium or plutonium. But overall, to date North Korea's revealed nuclear device reliability is about 66 percent. Pyongyang is clearly preparing for a fourth test, but has delayed it since early 2014, perhaps due to China's pressure. The North is likely to continue its nuclear testing unless some deals are made through the Six-Party Talks or DPRK-US bilateral talks, subject to having sufficient fissile material. (If the true stocks are very small, then additional tests for political or military reasons could reduce and even reverse the rate of weaponization and deployment.)        

Finally, miniaturization of nuclear warheads is likely the biggest obstacle to a missile-deliverable nuclear weapon. After the 2013 test, Pyongyang announced that the test “physically demonstrated the high performance of the DPRK's nuclear deterrent which has become smaller, lighter and diversified as it was a primary counter-measure in which it exercised its maximum self-restraint." Unsurprisingly, South Korea took this reference to a “smaller, lighter” weapon to mean that Pyongyang may be able to mount nuclear bombs on short-range missiles. In October 2014, General Curtis Scarlatti, head of US Forces Korea, stated that North Korea has the technology to make a small nuclear warhead and put it on a missile. But, he also added, he did not know if they had done so, and if they had, it would likely have low reliability. “We’ve not seen it tested at this point,” he stated. “Something that’s that complex, without it being tested, the probability of it being effective is pretty darn low.”

In sum, North Korea has already acquired nuclear warheads, conducted nuclear tests, has short- and intermediate-range missiles, and may have miniaturized warheads. But, when mated with unreliable missiles, the overall system probability of North Korean nuclear-armed missiles is likely to be very poor. Nonetheless, from the viewpoint of those receiving its verbal nuclear threats in the region and beyond, it is necessary to attribute some capability to the North (not just in missile delivery, but by bombers, ship, or ground delivery systems) and to adopt counter-measures. In short, nuclear threats from the North are no longer hypothetical but real and present.

Editor's note: This essay is part of a series of pieces about nuclear deterrence that Defining Ideas will be publishing in the weeks ahead. All of the essays are and will be from the new Hoover Press book, The War That Must Never Be Fought. To continue reading this essay, clichere.

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