Countries developing clandestine nuclear weapons programs usually go to great lengths to conceal information about these programs from the outside world. Therefore, obtaining reliable open source information on such programs is very challenging. The lack of reliable information typically results in substantial uncertainty about the size and capabilities of these clandestine programs.
Nonetheless, countries suspected of having clandestine nuclear weapons programs are the subject of intense scrutiny by nonproliferation analysts, intelligence agencies, and other observers. Gradually, a fuzzy picture emerges from the analysis, albeit with some gaps in understanding. The resulting analysis can set bounds on the uncertainties, while producing a range of estimates of the country's capabilities. Analytic tools include examining statements and articles in the news media, government reports including unclassified intelligence estimates, interviewing insiders who have had access to information about the clandestine program, reviewing secondary sources such as reports by analysts, and making scientific calculations based on the best available information about a country's nuclear infrastructure.
Technical analysis of clandestine programs is based on the widely known physical and engineering aspects of nuclear materials and weapons, which enable estimates of capabilities based on fragmentary and uncertain information, as follows.
Nuclear weapons programs require specialized materials, facilities, equipment, and training in order to produce the raw material for weapons--either highly enriched uranium (HEU) or plutonium--and then to fabricate explosive devices using this fissile material. Weapons programs can be based on indigenous (i.e., domestic) production capabilities, or they can rely on foreign supplies and technologies. Virtually all weapons programs use some foreign inputs, if only technical information culled from scientific and engineering sources. However, all countries known to have successfully acquired nuclear weapons have done so primarily on the basis of indigenously produced fissile material.
A plutonium-based bomb program requires capabilities to mine and mill uranium, process it into reactor fuel, transform the isotopic content of the fuel by "burning" it in a reactor, extract plutonium from the spent fuel, form the plutonium into the core of a fission-implosion weapon, and develop and test high explosives used to initiate fission. Although technically sub-optimal, even reactor-grade plutonium can be used as fissile material in nuclear weapons.
A uranium-based bomb program requires capabilities to mine and mill uranium, and to enrich it to weapons-grade or near-weapons-grade (the Hiroshima bomb used less-than-weapons-grade uranium).
An advanced weapons program would require the capability to manufacture tritium, a radioactive gas that can be used to enhance the explosive power of nuclear weapons, for fabrication of boosted-yield weapons.
While countries may seek to develop all of these capabilities on an independent, indigenous basis, they can and often do seek some inputs from foreign sources. For example, they may purchase raw or milled uranium ore from abroad, and then use indigenous facilities to enrich it to weapons-grade material.
Determining how many nuclear weapons a country can produce with a given amount of fissile material requires knowing the technological sophistication of the country and the explosive yield of the weapons. These specifications in North Korea are unknown. Based on data supplied by the de jure nuclear weapons states, the IAEA Safeguards Division defines quantities of concern as 8kg of plutonium and 25kg of HEU. However, sophisticated nuclear weapons reportedly use as little as 3-4kg of plutonium and/or 15-20kg of HEU. The Natural Resources Defense Council has estimated that a country with a "high technical capability" could require as little as 1kg of weapons-grade plutonium or 2.5kg HEU to produce a one kiloton bomb. The atomic bombs dropped on Hiroshima and Nagasaki used low-level nuclear weapons technology. The Hiroshima bomb, for example, employed about 50kg of 80% enriched uranium.
In the case of North Korea, determining the status of its nuclear weapons program is especially difficult. As an extremely isolated and secretive state, North Korea provides few signals of the existence--let alone the extent--of its nuclear weapons program. Key data sources for DPRK include defector testimony, which may be unreliable given possibility of deliberate disinformation by double agents and defectors exaggerating what they know, and unclassified estimates by US intelligence agencies, which may have certain biases based on national interest, worst-case expectations, domestic politics, etc. Also, most estimates do not rely on original texts in Korean, which may introduce some errors due to translation issues.
| Material |
Quantity |
Comments |
Safeguards |
| Highly Enriched Uranium (HEU) |
HEU (>20%; <90% enrichment) =
unknown[1] |
In October 2002, the DPRK allegedly acknowledged that it has a uranium enrichment program, according to US State Department officials. North Korea subsequently denied that it had such a program. |
IAEA[2] |
| HEU (>90% enrichment) = unknown |
| Plutonium |
Pu (reactor and fuel grade) = 0 |
The amount of Pu in spent fuel estimate factors in both the 5MW(e) and IRT reactors. |
IAEA[3] |
| Pu (weapons grade) = 6-10kg |
| Pu (in spent fuel) = 29-34kg |
| Nuclear Weapons |
Total = 1-3 |
|
N/A |
| Fission = 1-3 |
| Fusion = 0 |
[1] North Korea maintains an 8 MW(th) IRT-2000 research reactor, which uses 80% enriched uranium fuel. According to the IAEA, Russia has supplied this fuel in the past, but how much of this fuel North Korea still has available is uncertain. In July 1977, North Korea signed an INFCIRC/66 trilateral safeguards agreement with the IAEA. The IAEA inspections began in 1978. IAEA safeguards criteria prior to 1996 did not require a detailed analysis for reactors with thermal power ratings below 25MW(th), such as the IRT-2000 reactor; therefore, there is some concern that safeguards on the IRT reactor were not adequate. In 1987, North Korea upgraded the reactor to 8MW(th) and henceforth, it has required 80% enriched uranium fuel. This reactor was not frozen under the Agreed Framework.
[2] The HEU used for the IRT-2000 reactor was placed under IAEA safeguards in 1977. However, the DPRK's uranium enrichment program is not under IAEA safeguards, and as part of an undeclared nuclear weapons program, it violated North Korea's legal obligations under the Non-Proliferation Treaty (NPT). Because the DPRK has not signed the Additional Protocol to the IAEA safeguards system, IAEA inspectors were restricted from searching for and inspecting undeclared nuclear facilities.
[3] In late December 2002, North Korea dismissed the two IAEA inspectors verifying activities at the frozen nuclear facilities in Yŏngbyŏn-kun. On 10 January 2003, North Korea announced that it was withdrawing from the NPT. The treaty requires a 90-day waiting period before a withdrawal becomes effective. However, North Korea declared the withdrawal was immediate because 89 days had already elapsed in 1993 when Pyongyang first announced its intention to withdraw before "suspending its intention to withdraw."
 |
| |
Updated March 2003 |
|
|
