Nuclear proliferation

Nuclear weapons proliferation is one of the four big issues that have held back worldwide deployment of peaceful nuclear power. This article will address the proliferation questions raised in Nuclear power reconsidered.

As of 2022, countries with nuclear weapons have followed one or both of two paths in producing fissile materials for nuclear weapons: enrichment of uranium to very high fractions of U-235, or extraction of fissile plutonium (Pu-239) from irradiated uranium nuclear reactor fuel. The US forged the way on both paths during its World War II Manhattan Project. The fundamental aspects of both paths are well understood, but both are technically challenging. Even relatively poor countries can be successful if they have sufficient motivation, financial investment, and, in some cases, direct or illicit assistance from more technologically advanced countries.

The International Non-proliferation Regime

The International Atomic Energy Agency (IAEA) has a vigorous program to prevent additional countries from acquiring nuclear weapons. The Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is the cornerstone arrangement under which strategic rivals can trust, by independent international verification, that their rivals are not developing a nuclear weapons threat. The large expense of weapons programs makes it very unlikely that a country would start its own nuclear weapons program, if it knows that its rivals are not so engaged. With some notable and worrying exceptions, this program has been largely successful.

Paths to the Bomb

It is frequently claimed that building a civil nuclear power program adds to the weapons proliferation risk. There is an overlap in the two distinct technologies, after all. To build a bomb, one needs Highly Enriched Uranium (HEU) or weapons-grade plutonium (Pu-239). Existing reactors running on Low Enriched Uranium (LEU, under 5% U-235) or advanced reactors running on High Assay LEU (HALEU,up to 20% U-235) use the same technology that can enrich uranium to very high levels, but configured differently. Enrichment levels and centrifuge configurations can be monitored using remote cameras, on-site inspections, and installed instrumentation -- hence the value of international inspections by the IAEA. Using commercial power reactors as a weapons plutonium source is an extremely ineffective, slow, expensive, and easily detectable way to produce Pu. Besides the nuclear physics issues, refueling pressurized water reactors is both time-consuming and obvious to outside observers. That is why the US and other countries developed specialized Pu production reactors and/or uranium enrichment to produce fissile cores for nuclear weapons.

The Historical Record

While nuclear weapons proliferation is a matter of extreme importance, it is not apparent that it is a consequence of a country’s deployment of commercial nuclear reactors. Table 1 lists the countries with both nuclear weapons and operating commercial reactors (as of 2022). There are 33 countries/entities with operating commercial nuclear reactors. Eight, possibly nine, possess nuclear weapons, two of which developed weapons after developing commercial nuclear power. North Korea has nuclear weapons, but no power reactors. Iran is pursuing nuclear weapons, and has power reactors. The Joint Comprehensive Plan of Action (The Iran Nuclear Deal) was based on evidence that Iran’s new Bushehr Russian pressurized water reactors (VVERs) were not part of a weapons program, but that Iran’s uranium enrichment program and its uncompleted research reactor at Arak were.

Table 1. Correlation of commercial nuclear power programs with nuclear weapons programs.

Country	First Weapons1	First Commercial2	Comments
China	1964	1991	Uranium enrichment
France	1960	1963	UPGG Pu production reactor
India	1974	1969	Pu production reactor
Iran	-	2011	Enrichment seems to be the path so far, along with possible future use of the Arak research reactor
North Korea	2006	-	Pu production reactor
Pakistan	1998	1971	Small CANDU may have formed technological basis for Pu production reactors
Russia	1949	1963	Pu production reactor
UK	1952	1956	Pu production reactors and uranium enrichment
USA	1945	1960	Pu production reactors and uranium enrichment

¹Year of first nuclear weapons test.
²Year of first commercial reactor operation.

Future Threats and Barriers

Table 2. IAEA table of proliferation threats and barriers.

If nuclear power is to play a major role in decarbonizing our world, there will be thousands of new reactors in many countries, including some that may be tempted to acquire weapons. We must therefore answer some basic questions. Will deployment of reactors to untrusted countries, or countries that might be taken over by rogue actors, increase the risk of proliferation, either by theft of materials in the reactor, or by modification of the reactor to produce weapons-grade materials? Will fuel processing or other activities connected with nuclear power provide cover for a weapons program or a basis for a quick sprint to bomb making? Will knowledge of the new reactor designs or process technologies lead to easier ways to make bombs?

Answers to these questions can only be provided by looking at specific reactor designs. Some designs are safer than others. See the sections on proliferation in the articles linked under New_Reactor_Designs. We must also look in detail at specific threats and the combination of barriers we are counting on. Threats from a terrorist group trying to hide their activities are very different than from a big country with plenty of resources and a willingness to openly violate any treaties. See Table 2 for a summary from the International Atomic Energy Agency.

Preventing the proliferation of nuclear weapons requires at least one of the following in each country of concern (perhaps all countries) or of subnational groups:
1. Can we ensure no new countries can enrich uranium outside of NPT IAEA safeguards, are preparing to do so, or have done so? If a country decides to cheat, will this be detected in time to organize an appropriate international response?
2. Ditto weapons-grade plutonium or U-233 production. For advanced fuel cycles, what is the nature of the fissile materials?
3. Can weapons tests be detected?
4. Can we ensure no new countries can threaten others with nuclear weapons delivery systems? If a country decides to cheat, will this be detected in time to organize an appropriate international response?
5. Are safeguards adequate for preventing and detecting diversion of fissile materials from fuel recycling systems?