Order Code RL34256
North Korea’s Nuclear Weapons:
Latest Developments
Updated December 5, 2007
Mary Beth Nikitin
Analyst in WMD Nonproliferation
Foreign Affairs, Defense, and Trade Division

North Korea’s Nuclear Weapons: Latest Developments
Summary
This report summarizes what is known from open sources about the North
Korean nuclear weapons program — including weapons-usable fissile material and
warhead estimates — and assesses current developments in verifying dismantlement
of North Korea’s nuclear facilities as agreed in the Six-Party Talks. The Six-Party
Talks include the United States, South Korea, Japan, China, Russia, and North
Korea, and were begun in August 2003 to attempt to resolve the current crisis over
North Korean nuclear weapons.
Beginning in late 2002, North Korea ended an eight-year freeze on its plutonium
production program, expelled international inspectors, and restarted facilities. North
Korea may have produced enough additional plutonium for five nuclear warheads
since 2002. In total, it is estimated that North Korea has up to 50 kilograms of
separated plutonium, enough for at least half a dozen nuclear weapons. On February
10, 2005, North Korea announced that it had manufactured nuclear weapons for self-
defense and that it would bolster its nuclear weapons arsenal. On October 9, 2006,
North Korea conducted a nuclear test, with a yield of under 1 kiloton. The United
States and other countries condemned the test, and the United Nations Security
Council passed Resolution 1718 on October 14, 2006, that requires North Korea to
(1) refrain from nuclear or missile tests, (2) rejoin the Nuclear Nonproliferation
Treaty (NPT), and (3) abandon its weapons of mass destruction and ballistic missile
programs.
On February 13, 2007, North Korea reached an agreement with other members
of the Six-Party Talks to begin the initial phase (60 days) of implementing the Joint
Statement from September 2005 on denuclearization. Key components of the
agreement include halting production at the Yongbyon nuclear complex and delivery
of heavy fuel oil to North Korea. In July 2007, International Atomic Energy Agency
(IAEA) inspectors verified the shutdown of the Yongbyon facilities. On October 3,
2007, the Six Parties adopted a Joint Statement in which North Korea agreed to
disable the Yongbyon facilities and provide a declaration of all its nuclear programs
by December 31, 2007. The October 2007 statement said the United States would
lead disablement activities and provide the initial funding for those activities.
Much still remains to be confirmed regarding North Korea’s nuclear weapons
production capabilities and delivery systems, particularly regarding uranium
enrichment. Although U.S. officials confronted the North Koreans in 2002 with
intelligence that reportedly proved that Pyongyang was pursuing a uranium
enrichment program, U.S. intelligence officials have said they do not know where the
uranium program is based and have over time shown less confidence about what the
scope of the program might be. Further, although seismographs registered the
October 9, 2006, detonation and environmental sampling confirmed radioactivity,
uncertainty about the weapon’s design and sophistication remains. Additional
transparency on fissile material stocks and programs, including the uranium
enrichment program, may contribute to a better picture of North Korean nuclear
weapons capabilities. This report will be updated as events warrant.

Contents
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Weapons Production Milestones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Verification and “Disablement” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
The October 9, 2006, Nuclear Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Estimating Nuclear Warheads and Stocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Plutonium Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
A Uranium Enrichment Program? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Delivery Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Issues for Congress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

North Korea’s Nuclear Weapons:
Latest Developments
Background
In the early 1980s, U.S. satellites tracked a growing indigenous nuclear program
in North Korea. The North Korean nuclear program began in the late 1950s with
cooperation agreements with the Soviet Union on a nuclear research program near
Yongbyon. Its first research reactor began operation in 1967. North Korea used
indigenous expertise and foreign procurements to build a small nuclear reactor at
Yongbyon (5MWe). It was capable of producing about 6 kilograms (Kg) of
plutonium per year and began operating in 1986.1 Later that year, U.S. satellites
detected high explosives testing and a new plant to separate plutonium. In addition,
construction of two larger reactors (50MWe at Yongbyon and 200MWe at Taechon)
added evidence of a serious clandestine effort. Although North Korea had joined the
Nuclear Nonproliferation Treaty (NPT) in 1985 under Soviet pressure, safeguards
inspections began only in 1992, raising questions about how much plutonium North
Korea had produced covertly. In 1994, North Korea pledged, under the Agreed
Framework with the United States, to freeze its plutonium programs and eventually
dismantle them in return for several kinds of assistance.2 At that time, western
intelligence agencies estimated that North Korea had separated enough plutonium for
one or two bombs; other sources estimated four to five bombs. North Korea
complied with the Agreed Framework, allowing International Atomic Energy Agency
(IAEA) seals — including the “canning” of spent fuel rods at the Yongbyon reactor
— and permanent remote monitoring and inspectors at its nuclear facilities.
When in 2002, U.S. negotiators reportedly presented North Korean officials
with evidence of a clandestine uranium enrichment program, the North Korean
officials reportedly at first confirmed this, then denied it publicly. The conflict
quickly led to the breakdown of the Agreed Framework. The Bush Administration
argued that North Korea was in “material breach” of its obligations and, after
agreement with South Korea, Japan, and the EU (the other members of the Korean
Economic Development Organization, or KEDO), stopped the next shipment of
1 5MWe is a power rating for the reactor, indicating that it produces 5 million watts of
electricity per day (very small). Reactors are also described in terms of million watts of heat
(MW thermal).
2 See CRS Report RL33590, North Korea’s Nuclear Weapons Development and Diplomacy,
by Larry Niksch.

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heavy fuel oil.3 In response, North Korea kicked out international monitors, broke
the seals at the Yongbyon nuclear complex, and restarted its reactor and reprocessing
plant after an eight-year freeze.
Members of the Six-Party Talks — the United States, South Korea, Japan,
China, Russia, and North Korea — began meeting in August 2003 to try and resolve
the crisis. In September 2005, the Six Parties issued a Joint Statement on how to
achieve verifiable denuclearization of the Korean Peninsula, which formed the basis
for future agreements.4 After negotiations broke down, North Korea tested a nuclear
device in October 2006. The Denuclearization Action Plan of February 2007 called
for shut-down of facilities and provision of fuel oil to North Korea.5 Currently in the
second phase of this plan, the United States is working with North Korea to disable
key facilities and expects a full declaration of North Korea’s nuclear program by the
end of 2007.
The Denuclearization Action Plan does not include actions that will address
fissile material stocks, the uranium enrichment program, or dismantlement of
warheads and instead focuses on shutting down and disabling, for at least a year’s
time, the key plutonium production facilities. A later stage, to begin in January 2008,
is supposed to address all aspects of North Korea’s nuclear program, including
weapons, using North Korea’s declaration as a basis for future action. Understanding
the scope of the program and the weapons capability will require transparency and
careful verification for “complete, verifiable, irreversible” disarmament to be
achieved.
Weapons Production Milestones
Acquiring fissile material — plutonium-239 or highly enriched uranium (HEU)
— is the key hurdle in nuclear weapons development.6 Producing these two
materials is technically challenging; in comparison, many experts believe
weaponization to be relatively easy.7 North Korea has industrial-scale uranium
mining and plants for milling, refining, and converting uranium; it also has a fuel
fabrication plant, a nuclear reactor, and a reprocessing plant — in short, everything
needed to produce Pu-239. In its nuclear reactor, North Korea uses magnox fuel —
3 “Adherence To and Compliance With Arms Control, Nonproliferation and Disarmament
Agreements and Commitments,” U.S. Department of State, August 2005.
4 “Joint Statement of the Fourth Round of the Six-Party Talks, Beijing,” September 19,
2005, at [http://www.state.gov/r/pa/prs/ps/2005/53490.htm].
5 The United States authorized its first shipment of 50,000 metric tons of heavy fuel oil to
North Korea in September 2007. Peter Baker, “U.S. to Ship Fuel Oil to North Korea,” The
Washington Post
, September 29, 2007.
6 Highly enriched uranium (HEU) has 20% or more U-235 isotope; 90% U-235 is weapons-
grade.
7 The physical principles of weaponization are well-known, but producing a weapon with
high reliability, effectiveness, and efficiency without testing presents significant challenges.

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natural uranium (>99%U-238) metal, wrapped in magnesium-alloy cladding. About
8,000 fuel rods constitute a fuel core for the reactor.
When irradiated in a reactor, natural uranium fuel absorbs a neutron and then
decays into plutonium (Pu-239). Fuel that remains in the reactor for a long time
becomes contaminated by the isotope Pu-240, which can “poison” the functioning
of a nuclear weapon.8 Spent or irradiated fuel, which poses radiological hazards,
must cool after removal from the reactor. The cooling phase, estimated by some at
five months, is proportional to the fuel burn-up. Reprocessing to separate plutonium
from waste products and uranium is the next step. North Korea uses a PUREX
separation process, like the United States. After shearing off the fuel cladding, the
fuel is dissolved in nitric acid. Components (plutonium, uranium, waste) of the fuel
are separated into different streams using organic solvents. In small quantities,
separation can be done in hot cells, but larger quantities require significant shielding
to prevent deadly exposure to radiation.9
North Korea appears to have mastered the engineering requirements of
plutonium production. It has operated its nuclear reactor, is believed to have
separated Pu from the spent fuel, and has reportedly taken steps toward
weaponization. In January 2004, North Korean officials showed an unofficial U.S.
delegation alloyed “scrap” from a plutonium (Pu) casting operation.10 Dr. Siegfried
Hecker, a delegation member, assessed that the stated density of the material was
consistent with plutonium alloyed with gallium or aluminum. If so, this could
indicate a degree of sophistication in North Korea’s handling of Pu metal, necessary
for weapons production. But without testing the material, Hecker could not confirm
that the metal was plutonium or that it was alloyed, or when it was produced.
Verification and “Disablement”
In September 2005, North Korea agreed to abandon “all nuclear weapons and
existing nuclear programs,” but implementation of this goal was stalled.11 The
October 9, 2006, nuclear test is seen as a catalyst in uniting the other members of the
Six Party Talks to toughen their stance towards North Korea, and as a turning point
in Pyongyang’s attitude. UN Security Council Resolution 1718 calls on North Korea
8 Plutonium that stays in a reactor for a long time (reactor-grade, with high “burn-up”)
contains about 20% Pu-240; weapons-grade plutonium contains less than 7% Pu-240.
9 Hot cells are heavily shielded rooms with remote handling equipment for working with
irradiated materials. For background, see Jared S. Dreicer, “How Much Plutonium Could
Have Been Produced in the DPRK IRT Reactor?”Science and Global Security, 2000, vol.
8, pp. 273-286, at [http://www.princeton.edu/~globsec/publications/pdf/8_3Dreicer.pdf].
10 Alloying plutonium with other materials is “common in plutonium metallurgy to retain
the delta-phase of plutonium, which makes it easier to cast and shape” (two steps in
weapons production). Hecker, January 21, 2004, testimony before SFRC.
11 Joint Statement of the Fourth Round of Six Party Talks, Beijing, September 19, 2005, at
[http://www.state.gov/r/pa/prs/ps/2005/53490.htm].

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to abandon its nuclear weapons in a “complete, verifiable, and irreversible manner.”12
In February 2007, as part of implementation of the September 2005 Joint Statement,
North Korea committed to disable all nuclear facilities and provide a “complete and
correct” declaration of all its nuclear programs by December 31, 2007.13 The Bush
administration expects the declaration to include a full declaration of the separated
weapons-grade plutonium that has already been produced, as well as full disclosure
of uranium enrichment activities.14
The October 2007 joint statement said the United States would lead disablement
activities and provide the initial funding for those activities.15 Disablement indicates
a physical measure to make it difficult to restart operation of a facility while terms
are being worked out for its eventual dismantlement. U.S. officials have said that
they would prefer a disablement process that would require a 12-month time period
to start up the facility again.16 A team of U.S. technical experts in mid-October 2007
continued negotiations with the North Koreans on a plan that reportedly includes 10
discrete steps to disable the three main Yongbyon facilities related to North Korea’s
plutonium program (nuclear fuel fabrication plant, plutonium reprocessing plant, and
5-megawatt experimental nuclear power reactor).17 The first step will be to remove
the irradiated fuel from the reactor and store it in an adjacent cooling pond. The
specifics of the other nine steps (other than that there will be three for each facility)
have not yet been agreed upon.18 Disablement steps will need to be carefully chosen
in order to preserve information to completely verify the scope of the nuclear
program. The disablement process began in early November 2007.19 Japan is also
interested in contributing expertise, but it is not clear if this will be agreed to by
North Korea.20
12 United Nations Security Council Resolution 1718, October 14, 2006, at [http://daccessdds.
un.org/doc/UNDOC/GEN/N06/572/07/PDF/N0657207.pdf?OpenElement].
13 “Denuclearization Action Plan,” February 13, 2007, at [http://www.state.gov/r/pa/prs/
ps/2007/february/80479.htm].
14 On-The-Record Briefing: Assistant Secretary of State for East Asian and Pacific Affairs
and Head of the U.S. Delegation to the Six-Party Talks Christopher R. Hill, October 3, 2007,
at [http://www.state.gov/p/eap/rls/rm/2007/93234.htm].
15 Second Phase Actions for the Implementation of the September 2005 Joint Statement,
October 3, 2007, at [http://www.state.gov/r/pa/prs/ps/2007/oct/93223.htm].
16 On-the-Record-Briefing, U.S. Assistant Secretary of State Christopher Hill, October 3,
2007, at [http://www.state.gov/p/eap/rls/rm/2007/93234.htm].
17 “North Korea ‘Agrees to Nuclear Disablement Procedure,’” Chosun Ilbo, October 27,
2007.
18 David Albright and Paul Brannan, “Disabling DPRK Nuclear Facilities,” United States
Institute of Peace Working Paper, October 23, 2007.
19 “U.S. Team heads to N.K. to begin nuclear disablement,” Yonhap English News, October
31, 2007.
20 Japan Eyes Support for Disabling N. Korea Nuke Facilities,” Jiji Press English News
Service
, October 29, 2007.

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IAEA inspectors returned to North Korea in July 2007 to monitor and verify the
shut-down, install seals, and monitor facilities at the Yongbyon nuclear complex, and
have had a continuous presence there since then.21 In his September 10, 2007,
statement to the IAEA Board of Governors, Director General Mohamed ElBaradei
stated that the IAEA was able to verify the shutdown of nuclear facilities, including
the nuclear fuel fabrication plant, radio-chemical laboratory (reprocessing plant), and
the 5MWe experimental nuclear power reactor. Inspectors are also monitoring the
halt in construction of the 50-megawatt nuclear power plant at Yongbyon and the
200-megawatt nuclear power plant in Taechon.22 The United States has contributed
$1.8 million as the U.S. voluntary contribution and Japan has contributed $500,000
to the IAEA for their work in North Korea.23 In the future, the IAEA may be called
on to investigate North Korea’s past nuclear program in addition to monitoring
activities; however, to date, its role has been limited to monitoring the shut-down of
Yongbyon facilities. The IAEA’s role in disablement and future dismantlement
efforts has yet to be determined. Some analysts recommend an observer role for the
IAEA during disablement steps and continued IAEA monitoring to boost
international confidence in the process.24
Since IAEA inspectors were expelled from North Korea in 2002, information
about North Korea’s nuclear weapons production has depended on remote
monitoring and defector information, with mixed results. Satellite images correctly
indicated the start-up of the 5MWe reactor, but gave no details about its operations.
Satellites also detected trucks at Yongbyon in late January 2003, but could not
confirm the movement of spent fuel to the reprocessing plant;25 imagery reportedly
detected activity at the reprocessing plant in April 2003, but could not confirm large-
scale reprocessing;26 and satellite imagery could not peer into an empty spent fuel
pond, which was shown to U.S. visitors in January 2004. North Korean officials
stated in 2004 that the reprocessing campaign was conducted continuously (four six-
hour shifts). U.S. efforts to detect Krypton-85 (a by-product of reprocessing)
reportedly suggested that some reprocessing had taken place, but were largely
inconclusive. Even U.S. scientists visiting Pyongyang in January 2004 could not
confirm North Korean claims of having reprocessed the spent fuel or that the material
shown was in fact plutonium. Verifying those claims will require greater access to
the material and North Korean cooperation, and it is hoped that significant progress
21 “IAEA Team Confirms Shut Down of DPRK Nuclear Facilities,” IAEA press release, July
18, 2007,a t [http://www.iaea.org/NewsCenter/PressReleases/2007/prn200712.html].
22 GOV/2007/45-GC(51)/19, August 17, 2007.
23 Statement of Christopher R. Hill Assistant Secretary, Bureau of East Asian and Pacific
Affairs, Department of State before the House Committee on Foreign Affairs, Subcommittee
on Asia, the Pacific and the Global Environment and Subcommittee on Terrorism,
Nonproliferation and Trade, Joint Hearing on the North Korea Six-Party Process, October
25, 2007.
24 North Korea reportedly did not want the IAEA involved and wanted the United States to
do the disabling. Albright and Brannan, ibid.
25 “Reactor Restarted, North Korea Says,” Washington Post, February 6, 2003.
26 “US Suspects North Korea Moved Ahead on Weapons,” New York Times, May 6, 2003.

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will be made on these issues in 2008, after North Korean submits the declaration
detailing its nuclear program.
The next stage of verification, after disablement, will be the decommissioning
and dismantlement of the weapons production facilities. The terms for this work still
need to be negotiated. This stage may include a return of IAEA monitoring of
nuclear material stocks (including weapons-usable separated plutonium) and
verification of actual weapons dismantlement. The question of dismantling North
Korea’s nuclear warheads has not yet been addressed directly, although the
September 2005 joint statement commits North Korea to abandon all nuclear
weapons. Assistant Secretary Christopher Hill has said that the issue of which states
will participate in the verification is under discussion, but may include the nuclear-
weapon states amongst the six parties: the United States, Russia, and China. Critics
have raised concerns about the lack of clear verification provisions for these steps
and the omission of specific references to key issues such as fissile materials,
warheads, the reported uranium enrichment program, and the nuclear test site in the
latest agreements.27 In remarks to journalists, Assistant Secretary Hill has said that
warhead dismantlement will be addressed in the next stage — the “endgame” or the
“weapons phase” — which he hoped would start at the beginning of 2008.28
The October 9, 2006, Nuclear Test29
The U.S. Director of National Intelligence confirmed that North Korea
conducted an underground nuclear explosion on October 9, 2006, in the vicinity of
P’unggye.30 However, the sub-kiloton yield of the test suggests that the weapon
design or manufacturing process likely needs improvement.31 North Korea reportedly
told China before the test that it expected a yield of 4 kilotons, but seismic data
27 Ileana Ros-Lehtinen, “Verification Holds the Key,” The Washington Times, October 7,
2007; Sharon Squassoni, “Partial Progress,” The Guardian, October 9, 2007; Bruce
Klingner, “North Korea: Worrisome Gaps in Six-Party Talks’ Joint Statement,” Heritage
Foundation WebMemo
No. 1655, October 4, 2007.
28 On-the-Record Briefing by Assistant Secretary of State for East Asian and Pacific Affairs
and Head of the U.S. Delegation to the Six-Party Talks Christopher R. Hill On His
Upcoming Trip and the Six-Party Talks, U.S. State Department, August 29, 2007, at
[http://www.state.gov/r/pa/prs/ps/2007/aug/91612.htm].
29 See also CRS Report RL33709, North Korea’s Nuclear Test: Motivations, Implications,
and U.S. Options
, by Emma Chanlett-Avery and Sharon Squassoni.
30 “Analysis of air samples collected on October 11, 2006 detected radioactive debris which
confirms that North Korea conducted an underground nuclear explosion in the vicinity of
P.unggye on October 9, 2006. The explosion yield was less than a kiloton.” ODNI News
Release No. 19-06, at [http://www.dni.gov/announcements/20061016_release.pdf].
31 By comparison, a simple plutonium implosion device normally would produce a larger
blast, perhaps 5 to 20 kilotons. The first nuclear tests conducted by other states range from
9 kt (Pakistan) to 60kt (France), but tests by the United States, China, Britain, and Russia
were in the 20kt-range.

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confirmed that the yield was less than 1 kt.32 Radioactive debris indicates that the
explosion was a nuclear test, and that a plutonium device was used.33 It is widely
believed that the warhead design was an implosion device.34 Uncertainties remain
about when the plutonium used for the test was produced and how much plutonium
was in the device, although a prominent U.S. nuclear scientist has estimated that
North Korea likely used approximately 6 kg of plutonium for the test.35
The test’s low yield may not have been a failure. Another possibility is that the
test’s low yield was intentional — a sophisticated device designed for a Nodong
medium range missile. Alternatively, a low yield could have been intended to avoid
radioactive leakage from the test site or to limit the amount of plutonium used.36
Estimating Nuclear Warheads and Stocks
Secretary of State Colin Powell in December 2002 stated, “We now believe [the
North Koreans] have a couple of nuclear weapons and have had them for years.”37
In February 2005, North Korea officially announced that it had “manufactured nukes
for self-defense.”38 Although North Korea has tested one device, Vice Foreign
Minister Kim Gye Gwan has previously said that North Korea possesses multiple
bombs and was building more.39
A key factor in assessing how many weapons North Korea can produce is
whether North Korea needs to use more or less material than the IAEA standards of
32 Mark Mazzetti, “Preliminary Samples Hint at North Korean Nuclear Test,” New York
Times
, October 14, 2006, at [http://www.nytimes.com/2006/10/14/world/asia/14nuke.html].
33 Thom Shanker and David Sanger, “North Korean fuel identified as plutonium,” New York
Times,
October 17, 2006, at [http://www.nytimes.com/2006/10/17/world/asia/17diplo.html].
A debate on this issue can be found in the November 2006 issue of Arms Control Today, at
[http://armscontrol.org/act/2006_11/tech.asp#Sidebar1].
34 Implosion devices, which use sophisticated lenses of high explosives to compress fissile
material, are generally thought to require testing, although the CIA suggested in 2003 that
North Korea could validate a simple fission nuclear weapons design using extensive high
explosives testing. CIA response to questions for the record, August 18, 2003, submitted
by the Senate Select Committee on Intelligence, at [http://www.fas.org/irp/congress/
2003_hr/021103qfr-cia.pdf].
35 Siegfried Hecker, “Report on North Korean Nuclear Program,” Center for International
Security and Cooperation, Stanford University, November 15, 2006.
36 Siegfried Hecker, “Report on North Korean Nuclear Program,” Center for International
Security and Cooperation, Stanford University, November 15, 2006.
37 Transcript of December 29, 2002, Meet the Press.
38 James Brooke, “North Korea says it has atom arms It will boycott talks on ending
program; arsenal called self-defense against Bush,” The New York Times, February 11, 2005.
39 “We have enough nuclear bombs to defend against a U.S. attack. As for specifically how
many we have, that is a secret.” “North Korea Admits Building More Nuclear Bombs,”
ABC News, June 8, 2005, at [http://abcnews.go.com/WNT/story?id=831078&page=1].

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8kg of Pu and 25kg for HEU per weapon40. The amount of fissile material used in
each weapon is determined by the design sophistication. There is no reliable public
information on North Korean nuclear weapons design.
In all, estimates of North Korea’s separated plutonium range between 30 and 50
kg, with an approximate 5 to 6 kg of this figure having been used for the October
2006 test.41 This amounts to enough plutonium for approximately five to eight
nuclear weapons, assuming 6 kg per weapon. After the test, North Korean could
possess four to seven nuclear weapons. An unclassified intelligence report to
Congress says that “prior to the test North Korea could have produced up to 50 kg
of plutonium, enough for at least a half dozen nuclear weapons” and points out that
additional plutonium is in the fuel of the Yongbyon reactor.42 Under Secretary
Christopher Hill has also cited the 50 kg estimate.43
Additional questions arise in determining how much plutonium North Korea has
produced since 2002 when the IAEA monitors were kicked out of the country and the
seals were broken at Yongbyon. A South Korean Defense Ministry white paper from
December 2006 estimated that North Korea had made 30 kg of weapons-grade
plutonium in the previous three years, potentially enough for five nuclear bombs. It
also concurred with U.S. estimates that North Korea’s total stockpile of weapons-
grade plutonium was 50 kg.44
Plutonium Production
Estimates of plutonium production depend on a variety of technical factors,
including the average power level of the reactor, days of operation, how much of the
fuel is reprocessed and how quickly, and how much plutonium is lost in production
processes. North Korean officials claimed to have separated plutonium in hot cells
as early as 1975 and tested the reprocessing plant in 1990. North Korea’s 5MWe
nuclear reactor at Yongbyon operated from 1986 to 1994. It is estimated that North
40 IAEA Safeguards Glossary: [http://www-pub.iaea.org/MTCD/publications/PDF/nvs-3-cd/
PDF/NVS3_scr.pdf].
41 Siegfried Hecker estimates 40-50 kg of separated plutonium and 6 kg for the test; David
Albright and Paul Brannan’s study says 33-55 kg of separated plutonium and roughly 5 kg
for the test. U.S. Assistant Secretary of State Christopher Hill cites 50 kg in his comments.
Hecker, ibid. David Albright and Paul Brannan, “The North Korean Plutonium Stock
February 2007,” Institute for Science and International Security, February 20, 2007.
Christopher Hill, “Interview on PBS NewsHour,” October 3, 2007, at [http://www.state.gov/
p/eap/rls/rm/2007/93274.htm].
42 Unclassified Report to Congress on Nuclear and Missile Programs of North Korea, Office
of the Director of National Intelligence, August 8, 2007.
43 Joint Hearing on the North Korea Six-Party Process, House Committee on Foreign
Affairs, Subcommittee on Asia, the Pacific and the Global Environment and Subcommittee
on Terrorism, Nonproliferation and Trade, October 25, 2007.
44 “North Korea ‘serious threat’ to South,” BBC News, [http://news.bbc.co.uk/2/hi/
asia-pacific/6216385.stm].

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Korea produced and separated no more than 10 kg of plutonium prior to 1994.45 Its
plutonium production program was then frozen between 1994 and 2003 under the
Agreed Framework. When this agreement was abandoned, North Korea restarted
plutonium production at Yongbyon.
On February 6, 2003, North Korean officials announced that the 5MWe reactor
was operating, and commercial satellite photography confirmed activity in March.
In January 2004, North Korean officials told an unofficial U.S. delegation that the
reactor was operating smoothly at 100% of its rated power. The U.S. visitors noted
that the display in the reactor control room and steam plumes from the cooling towers
confirmed operation, but that there was no way of knowing how it had operated over
the last year.46
The same delegation reported that the reprocessing “facility appeared in good
repair,” in contrast to a 1992 IAEA assessment of the reprocessing plant as
“extremely primitive.” According to North Korean officials in January 2004, the
reprocessing plant’s annual throughput is 110 tons of spent fuel, about twice the fuel
load of the 5MWe reactor. Officials claimed to have reprocessed all 8,000 fuel rods
from the 5MWe reactor between January and June 2003.47 Reprocessing the 8,000
fuel rods would yield between 25 and 30kg of plutonium, perhaps for four to six
weapons, but the exact amount of plutonium that might have been reprocessed is
unknown. In 2004, North Korean officials stated that the reprocessing campaign was
conducted continuously (in four six-hour shifts).
In April 2005, the 5MWe reactor was shut down, this time to harvest fuel rods
for weapons.48 The reactor resumed operations in June 2005.49 One estimate is that
the reactor held between 10 and 15 kg of Pu in April 2005, and that North Korea
could have reprocessed all the fuel rods by mid-2006. From August 2005 to 2006,
the reactor could have produced another 6 kg of Pu. In total, North Korea could have
reprocessed enough separated plutonium for another three weapons (in addition to
the estimated 4-6 bomb-worth from reprocessing the 8,000 fuel rods).50 The 5MWe
45 David Albright and Paul Brannan, “The North Korean Plutonium Stock February 2007.”
46 Siegfried Hecker, January 21, 2004, testimony before Senate Foreign Relations
Committee.
47 “North Korea Says It Has Made Fuel For Atom Bombs,” New York Times, July 15, 2003.
48 “North Koreans Claim to Extract Fuel for Nuclear Weapons,” New York Times, May 12,
2005.
49 David Albright and Paul Brannan, “The North Korean Plutonium Stock February 2007,”
Institute for Science and International Security, February 20, 2007.
50 Technical difficulties associated with the fuel fabrication facility may have slowed how
often the fuel was unloaded from the reactor, limiting production to at most one bomb per
year. Siegfried Hecker, “Report on North Korean Nuclear Program,” Center for
International Security and Cooperation, Stanford University, November 15, 2006.

CRS-10
reactor was again shut down in July 2007, when the IAEA installed containment and
surveillance measures and radiation monitoring devices.51
The reactors at Yongbyon (50MWe) and Taechon (200MWe) are several years
from completion. No construction has occurred at the 50MWe reactor or at the
200MWe reactor since 2002.52 U.S. visitors in January 2004 saw heavy corrosion
and cracks in concrete building structures at Yongbyon, reporting that the reactor
building “looks in a terrible state of repair.”53 The CIA estimated that the two
reactors could generate about 275kg of plutonium per year if they were operating.54
Dr. Hecker estimated that if the 50MWe reactor was functioning, it would mean a
tenfold increase in North Korea’s plutonium production.55 North Korea agreed to
halt work on reactors as part of the Six Party Talks. As of July 2007, the IAEA is
monitoring to ensure that no further construction takes place at these sites.
Significant future growth in North Korea’s arsenal would be possible only if the
two larger reactors were completed and operating, and would depend on progress in
the reported uranium enrichment program. With construction of the 50MWe and
200MWe reactors shuttered and the Yongbyon facilities awaiting disablement and
eventual dismantlement, North Korean plutonium production for the moment has
stopped. The reprocessing facility is also now shut down and under IAEA
monitoring. However, even with the reprocessing facility shut down, North Korea
could build additional warheads with existing separated plutonium because North
Korea’s plutonium stocks are not yet under IAEA safeguards.
A Uranium Enrichment Program?
While North Korea’s weapons program has been plutonium-based from the
start, in the last decade, intelligence has emerged pointing to a second route to a
bomb using highly enriched uranium. There is some certainty that North Korea has
parts and plans for such a program, and less certainty over how far this program has
developed. The issue has been central to negotiations since October 2002, when the
Bush Administration accused North Korea of having a clandestine uranium
enrichment program. U.S. lead negotiator James Kelly told North Korean First
Deputy Foreign Minister Kang Sok-chu that the United States had evidence of a
uranium enrichment program for nuclear weapons in violation of the Agreed
Framework and other agreements. James Kelly said that Kang acknowledged the
existence of such a program at that meeting. However, Kang later denied this, and
51 IAEA Team Confirms Shut Down of DPRK Nuclear Facilities, [http://www.iaea.org/
NewsCenter/PressReleases/2007/prn200712.html].
52 Report by the Director General to the IAEA Board of Governors, “Applications of
Safeguards in the Democratic People’s Republic of Korea (DPRK),” GOV/2007/45-
GC(51)/19, August 17, 2007.
53 Hecker January 21, 2004, testimony before SRFC.
54 CIA unclassified point paper distributed to congressional staff on November 19, 2002.
55 Siegfried Hecker, “Report on North Korean Nuclear Program,” Center for International
Security and Cooperation, Stanford University, November 15, 2006.

CRS-11
Foreign Minister Paek Nam Sun said that Kang had told Kelly that North Korea is
“entitled” to have such a program or “an even more powerful one” to deter a pre-
emptive U.S. attack.56
A 2002 unclassified CIA working paper on North Korea’s nuclear weapons and
uranium enrichment estimated that North Korea “is constructing a plant that could
produce enough weapons-grade uranium for two or more nuclear weapons per year
when fully operational — which could be as soon as mid-decade.” Such a plant
would need to produce more than 50kg of HEU per year, requiring cascades of
thousands of centrifuges.57 The paper noted that in 2001, North Korea “began
seeking centrifuge-related materials in large quantities.” Pakistani President
Musharraf revealed in his September 2006 memoir, In the Line of Fire, that Abdul
Qadeer Khan — chief scientist in Pakistan’s nuclear weapons program who
proliferated nuclear weapons technology for profit — “transferred nearly two dozen
P-1 and P-2 centrifuges to North Korea. He also provided North Korea with a flow
meter, some special oils for centrifuges, and coaching on centrifuge technology,
including visits to top-secret centrifuge plants.”58 However, the United States has not
been able to get direct confirmation from Khan. According to press reports, North
Korea said it had imported 150 tons of high-strength aluminum tubes from Russia
that could be used in a uranium enrichment program.59
Questions have been raised about whether the 2002 estimates were accurate.60
In a hearing before the Senate Armed Services Committee on February 27, 2007,
Joseph DeTrani, the mission manager for North Korea from the Office of the
Director of National Intelligence and former chief negotiator for the Six Party Talks,
was asked by Senator Jack Reed whether he had “any further indication of whether
that program has progressed in the last six years, one; or two, the evidence — the
credibility of the evidence that we had initially, suggesting they had a program rather
than aspirations?” DeTrani responded that “the assessment was with high confidence
that, indeed, they were making acquisitions necessary for, if you will, a
production-scale program. And we still have confidence that the program is in
56 Selig Harrison, “Did North Korea Cheat?” Foreign Affairs, vol. 84, no. 1,
January/February 2005.
57 North Korea would first have to convert uranium “yellowcake” into uranium hexaflouride
to feed into the centrifuges. The centrifuges would “enrich” the uranium, or increase the
portion of U-235. Weapons-grade enriched uranium according to the IAEA needs to have
an enrichment level of at least 20%. See CRS Report RL34234, Managing the Nuclear Fuel
Cycle: Policy Implications of Expanding Global Access to Nuclear Power
, by Mary Beth
Dunham Nikitin, Jill Marie Parillo, Sharon Squassoni, Anthony Andrews, and Mark Holt.
58 Pervez Musharraf, In the Line of Fire: A Memoir, (New York: Free Press, September
2006), p. 296.
59 “NK Admits to Buying Aluminum Tubes,” KBS World News, September 27, 2007, and
Takashi Sakamoto,”DPRK Admits To Importing Aluminium Tubes From Russia for
Uranium Enrichment,” Yomiuri Shimbun, in Japanese, Translated by BBC Monitoring Asia
Pacific
, October 26, 2007.
60 Paul Kerr, “News Analysis: Doubts Rise on North Korea’s Uranium-Enrichment
Program,” Arms Control Today, April 2007, at [http://www.armscontrol.org/act/2007_04/
NewsAnalysis.asp].

CRS-12
existence — at the mid-confidence level.” In a clarification of his response, DeTrani
issued a DNI press release that said there was a high level of confidence in 2002 that
North Korea had a uranium enrichment program, and “at least moderate confidence
that North Korea’s past efforts to acquire a uranium enrichment capability continue
today.”61 Assistant Secretary Christopher Hill said in February 2007 that the United
States is not sure if North Korea has mastered “some considerable production
techniques,” although they have acquired some technology for an enrichment
program.62
The most recent DNI unclassified report of August 2007 stated,
We continue to assess with high confidence that North Korea has pursued efforts
to acquire a uranium enrichment capability, which we assess is intended for
nuclear weapons. All Intelligence Community agencies judge with at least
moderate confidence that this past effort continues. The degree of progress
towards producing enriched uranium remains unknown, however.63
The confidence level of these assessments may have changed because of a
decrease in international procurement by North Korea. Uranium enrichment-related
imports would be more easily detected by intelligence agencies than activities inside
North Korea itself. Uranium enrichment facilities can be hidden from aerial
surveillance more easily than plutonium facilities, making it more difficult for
intelligence agencies to even detect — thus, “degree of progress” in turning the
equipment into a working enrichment program is “unknown.” Furthermore, there are
significant differences between assembling a small-scale centrifuge enrichment
program and operating a large-scale production plant, and reportedly little evidence
of procurement for a large-scale plant has emerged.64
As part of the February 2007 agreement in the Six-Party talks, North Korea
agreed to provide a “complete declaration of all nuclear programs and disablement
of all existing nuclear facilities,” and has pledged to do so by the end of 2007. U.S.
61 “There has been considerable misinterpretation of the Intelligence Community’s view of
North Korean efforts to pursue a uranium enrichment capability. The intelligence in 2002
was high quality information that made possible a high confidence judgment about North
Korea’s efforts to acquire a uranium enrichment capability. The Intelligence Community
had then, and continues to have, high confidence in its assessment that North Korea has
pursued that capability. We have continued to assess efforts by North Korea since 2002.
All Intelligence Community agencies have at least moderate confidence that North Korea’s
past efforts to acquire a uranium enrichment capability continue today.” ODNI News
Release 04-07, March 4, 2007, at [http://www.dni.gov/press_releases/20070304_release.
pdf].
62 “Update on the Six Party Talks,” Brookings Institution, February 22, 2007, at
[http://www.brookings.edu/events/2007/0222south-korea.aspx].
63 Unclassified Report to Congress on Nuclear and Missile Programs of North Korea, Office
of the Director of National Intelligence, August 8, 2007.
64 See David Albright, “North Korea’s Alleged Large-Scale Enrichment Plant: Yet Another
Questionable Extrapolation Based on Aluminum Tubes,” The Institute for Science and
Security, February 23, 2007, at [http://www.isis-online.org/publications/dprk/DPRK
enrichment22Feb.pdf].

CRS-13
officials have said that this will include any uranium enrichment activities. Assistant
Secretary Christopher Hill in testimony to Congress in October 2007 said that he
expects transparency on the uranium enrichment program by the end of 2007.65
North Korea reportedly continues to deny the existence of a highly enriched
uranium program for weapons. A Washington Post report on November 10, 2007,
said North Korea has given evidence to the United States in an effort to prove that
it never intended to produce highly enriched uranium for weapons, and that the
imported materials were for conventional weapons or dual-use projects. A senior
U.S. official is quoted as saying, “They have shown us some things, and we are
working it through. Some explanations make sense; some are a bit of a stretch.”66
Christopher Hill on November 15 after meeting with IAEA Director General El
Baradei about North Korean disablement said that their was “some progress” on the
issue, but declined to discuss details.67
Delivery Systems
Although former Defense Intelligence Agency (DIA) Director Lowell Jacoby
told the Senate Armed Services Committee in April 2005 that North Korea had the
capability to arm a missile with a nuclear device, Pentagon officials later backtracked
from that assessment. A DNI report to Congress says that “North Korea has short
and medium range missiles that could be fitted with nuclear weapons, but we do not
know whether it has in fact done so.”68 North Korea has several hundred short-range
Scud-class and medium range No Dong-class ballistic missiles, and is developing an
intermediate range ballistic missile. The Taepo-Dong-2 that was tested
unsuccessfully in July 2006 would be able to reach the continental United States if
it becomes operational.
It is possible that Pakistani scientist A.Q. Khan may have provided North Korea
the same Chinese-origin nuclear weapon design he provided to Libya and Iran. Even
though that design was for an HEU-based device, it would still help North Korea
develop a reliable warhead for ballistic missiles — small, light, and robust enough
to tolerate the extreme conditions encountered through a ballistic trajectory.
65 Statement of Christopher R. Hill Assistant Secretary, Bureau of East Asian and Pacific
Affairs, Department of State before the House Committee on Foreign Affairs, Subcommittee
on Asia, the Pacific and the Global Environment and Subcommittee on Terrorism,
Nonproliferation and Trade, Joint Hearing on the North Korea Six-Party Process, October
25, 2007.
66 Glenn Kessler, “N. Korea Offers Evidence to Rebut Uranium Claims,” The Washington
Post
, November 10, 2007.
67 “U.S. Reports Progress on North Korean Uranium Issue,” Global Security Newswire,
November 14, 2007.
68 Unclassified Report to Congress on Nuclear and Missile Programs of North Korea, Office
of the Director of National Intelligence, August 8, 2007. Also see CRS Report RS21473,
North Korean Ballistic Missile Threat to the United States, by Steven A. Hildreth.

CRS-14
Learning more about what is needed for miniaturization of warheads for ballistic
missiles could have been the goal of North Korea’s testing a smaller nuclear device.69
Issues for Congress
Congress will have a clear role in considering U.S. funding for the disablement
and decommissioning of North Korea’s nuclear facilities, as well as other
inducements for cooperation as agreed in the Six Party talks. For example, the
President has submitted a request to Congress for $106 million “to provide Heavy
Fuel Oil or an equivalent value of other assistance to North Korea on an ‘action-for-
action’ basis in support of the Six Party Talks in return for actions taken by North
Korea on denuclearization” as part of the 2008 War Funding Request.70
In addition, Congress may influence the course of the negotiations with North
Korea through legislation that limits or places requirements on U.S. diplomatic
actions. For example, H.R. 3650 has been introduced and referred to the House
Foreign Affairs Committee, calling for certification by the President that North Korea
has met a range of nonproliferation and political benchmarks before lifting any U.S.
sanctions imposed because it has been deemed a supporter of international terrorism
by the Secretary of State.71 Congress could also establish reporting requirements on
progress, or condition appropriations or disbursement to North Korea upon
verification measures. Congress could also be involved in other aspects of potential
changes in U.S. relations with Pyongyang, such as removal from the state sponsors
of terrorism list, monitoring of the North Korean human rights issues, funding for
further denuclearization steps including verification provisions, and establishment
of normalized ties once nuclear dismantlement has been achieved.
crsphpgw
69 “Technical Perspective on North Korea’s Nuclear Test: A Conversation between Dr.
Siegfried Hecker and Dr. Gi-Wook Shin,” Stanford University website, October 10, 2006,
at [http://aparc.stanford.edu/news/technical_perspective_on_north_koreas_nuclear_test_a_
conversation_between_dr_siegfried_hecker_and_dr_giwook_shin_20061010//].
70 2008 War Funding Request, October 22, 2007, at [http://www.whitehouse.gov/news/
releases/2007/10/20071022-7.html].
71 H.R. 3650, September 25, 2007.