Nuclear proliferation

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 (HEU, or Highly Enriched Uranium), or extraction of fissile plutonium (Pu) from irradiated uranium nuclear reactor fuel. Both paths are technically challenging but achievable. 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 potential nuclear opponents are not developing a nuclear weapons threat. The large expense of weapons programs makes it very unlikely that a country that knows its rivals are not so engaged would anyway start or maintain its own nuclear weapons program. With some notable and worrying exceptions, this has been largely successful.

Paths to the Bomb

It is frequently claimed that building a civil nuclear power program produces a weapons proliferation risk. There is an overlap in the two distinct technologies, after all. To build a bomb, one needs enough fissile material (highly enriched uranium or weapons-grade plutonium) to fuel the explosion. Enriching uranium to levels needed by existing reactors (under 5%, or LEU) or advanced nuclear reactors (some near 20%, or high-assay LEU) is the same technology that can enrich uranium to very high levels, but configured differently. Enrichment levels and centrifuge configurations can presumably 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, easily detectable way to produce Pu for weapon use. Besides the nuclear physics issues, refueling power 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 possess nuclear weapons, five of which developed commercial nuclear power after producing weapons. (North Korea does not operate power reactors, but does have nuclear weapons.) The Joint Comprehensive Plan of Action (The Iran Nuclear Deal) was based on the 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	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.