Nuclear Power Export Risks and How They Fuel Proliferation

The relationship between nuclear power and nuclear proliferation is a critical global concern, particularly regarding the export of nuclear technology. While the United States isn't worried about its civilian reactors being repurposed for weapons, the export of nuclear power technology to other nations presents a complex challenge. This is especially relevant as nuclear power is seen as a way to reduce CO2 emissions in countries without access to abundant wind and solar, and an export market could be a lifeline for the US nuclear industry, which currently struggles with competitiveness against renewables.

The core issue is that the equipment and materials within the nuclear fuel cycle can be adapted for making nuclear weapons. Proliferation involves both a political decision and technical capabilities. The technical feasibility of developing nuclear weapons can influence a nation's political decision to pursue them. For instance, countries like Iraq, Libya, and Iran initiated nuclear weapons programs after being offered black market nuclear technology, suggesting that the availability of technology can spark such ambitions.

Factors Predicting Nuclear Weapons Acquisition

Research by political science professor Matt Fuhrman, analyzing thousands of civilian nuclear assistance agreements between 1945 and 2000, identified three significant factors correlating with a country's acquisition of nuclear weapons:

• Peaceful nuclear cooperation: This suggests that engagement in civilian nuclear programs increases the probability of future weapons pursuit.
• Militarized dispute: Countries involved in conflicts are more likely to seek nuclear weapons.
• GDP per capita: Wealthier nations may perceive themselves as leading powers and thus pursue nuclear capabilities.

While peaceful nuclear cooperation doesn't directly cause proliferation, it increases the likelihood that a future event could lead a nation to develop weapons. This creates a tension between nuclear power advocates, who emphasize other contributing factors, and those focused on non-proliferation, who highlight the technological link.

The Proliferation Risk: A Thought Experiment

Consider a country like Saudi Arabia, a wealthy regional power with adversaries (Israel, Iran) that possess or have pursued nuclear weapons, and an ally (Pakistan) that has them. Such a nation might feel compelled to acquire nuclear weapons for defense.

To build a nuclear weapon, a country would first need to decide on the type:

1. Gun-type weapon: This design, exemplified by the Hiroshima bomb, involves shooting one piece of fissile material (highly enriched uranium) into another to achieve a nuclear explosion. It is simple to make, requires no advanced engineering, and is considered low-risk. The primary challenge is obtaining highly enriched uranium (HEU), defined as uranium enriched to over 20%. Even uranium enriched to 19.75% (technically below the HEU threshold) could be used to make a weapon, raising concerns about exporting reactors that use such fuel.
2. Implosion-type weapon: This design, like the Nagasaki bomb, uses conventional explosives to compress a core of fissile material (typically plutonium) to achieve criticality. This is more complex than the gun-type design but is the basis for most modern nuclear weapons. Plutonium cannot be used in a gun-type design due to its spontaneous fission, which would cause pre-ignition.

Fissile Materials and Their Proliferation Potential

Beyond uranium-235 and plutonium-239, several other isotopes can, in principle, be used to make nuclear weapons. However, many are impractical due to:

• Low production quantities: Curium isotopes.
• Difficulty in production: Light uranium isotopes (U-233, U-234) and neptunium-236.
• Short half-lives: Americium, plutonium-241, uranium-232, making them "hot" and difficult to handle. The thorium fuel cycle, often touted as proliferation-resistant, can produce uranium-233, which is an excellent weapons material. The proliferation resistance of thorium depends on the assumption that proliferators would not chemically separate protactinium-233 before it decays into uranium-233, thus avoiding the production of highly radioactive uranium-232.
• Large critical mass: Uranium-234.

The key takeaway is that almost any fissile material, in sufficient quantities, can be made into an explosive device. Mixing different isotopes might alter the critical mass but does not "denature" the material to make it unusable for weapons. This is particularly relevant to "reactor-grade plutonium," which, despite containing more higher plutonium isotopes, is still weapons-usable. The US Department of Energy explicitly states that reactor-grade plutonium can be used to build effective nuclear weapons, even by unsophisticated proliferators. The main difference is that weapon-grade plutonium is preferred for safety reasons and ease of handling by military personnel.

Technical Connections to Nuclear Power

The primary concern is preventing the diversion of plutonium from spent fuel or the use of enrichment processes to create HEU. While making the weapons themselves is not overly complicated (demonstrated in 1945 and by North Korea), obtaining the fissile material is the hard part.

Once-Through Fuel Cycle: In this cycle, used in the US, uranium is burned in reactors, and the spent fuel is stored. At no point is directly weapons-usable material present. The uranium enrichment is too low for weapons, and while spent fuel contains plutonium, it is mixed with highly radioactive fission products, requiring a reprocessing plant to separate it. This has been the foundation of non-proliferation since the Ford administration.

Reprocessing and Fast Reactors: The problem arises with reprocessing, which separates plutonium from spent fuel. This creates a dedicated pathway to weapons material without needing additional facilities. Countries like France and Japan engage in reprocessing, leading to significant IAEA inspection efforts due to the proximity to weapons capability.

Dedicated Production Facilities: Most countries with nuclear weapons have used dedicated production reactors, not civilian power reactors. However, some countries have contemplated or attempted to use civilian power reactors for weapons production:

• France and the UK: Both made weapons using their power reactors.
• Argentina, Brazil, Sweden, Taiwan: All had programs to divert fuel from power reactors for weapons. US intervention or cost issues led to the abandonment of these programs.

Plutonium Production in Power Reactors: To obtain weapons-grade plutonium from power reactors, fuel needs to be removed early, before it accumulates too many undesirable isotopes. This can be done by:

• Early shutdown and refueling: This might raise suspicions but can be disguised as maintenance.
• Using initial fuel loads: The first batch of fuel in a PWR has lower enrichment and is burned less, yielding plutonium of good quality.
• CANDU reactors: These heavy water reactors use natural uranium and produce more plutonium, making them particularly problematic from a proliferation standpoint. India and South Korea initially used CANDU reactors, providing them with a cache of potential weapons material.

Dedicated Pathways to Weapons

Countries can also pursue dedicated programs to produce fissile material, often under the guise of civilian nuclear power:

• Plutonium production reactors: Countries can build dedicated reactors designed to produce plutonium. Iran's Arak reactor, for example, was a natural uranium-fueled heavy water reactor capable of producing significant quantities of weapons-grade plutonium. Such projects are large and difficult to keep secret, often requiring a civilian nuclear power justification.
• Uranium enrichment plants: Historically considered difficult, the development of gas centrifuges has made uranium enrichment more accessible. Countries like Pakistan, Iraq, Iran, Libya, and North Korea have pursued this path. Again, the existence of a civilian power reactor provides an excuse for an enrichment program, making it harder to challenge under the NPT.

The connection to civilian nuclear power is crucial because it provides a plausible cover for activities that could lead to weapons development. Without the pretext of civilian energy needs, it would be much harder for countries to justify building facilities that could be repurposed for weapons. This is why the export of nuclear power technology, even for peaceful purposes, remains a significant non-proliferation challenge.