Dolphin Class Submarine. Credit:Thyssen Krupp - Photo: 2023

Should We Fear Nuclear Submarine Proliferation?

Evil is in the eye of the beholder

By Leonam dos Santos Guimarães Capt. (ret.) Brazilian Navy*

RIO DE JANEIRO, 11 May 2023 (IDN) — The potential cause-effect relationship between nuclear attack submarine development and nuclear weapons production by Non-Proliferation Treaty/nonnuclear-weapons states is a subject that has been scarcely discussed in unclassified sources until the trilateral security pact between Australia, the United Kingdom, and the United States (AUKUS), announced on 15 September 2021 for the Indo-Pacific region.

The issue can be stated as follows: Given their cost, environmental impact, and possible connection to the proliferation of nuclear weapons, are nuclear attack submarines the most appropriate naval technology for facing realistic threats to the national security of a particular non-nuclear weapons state?

The debate on the wisdom of nuclear attack submarine acquisition is reminiscent of the long-standing controversy over the desirability of using nuclear power as an energy source in developing countries—in particular states—without nuclear weapons.

The connection between nuclear power and the spread of nuclear weapons arose after India’s first nuclear-weapon test in 1974, and from the perception that the use of nuclear power would expand rapidly after the 1973 oil crisis.

The conventional wisdom was that the establishment of a civilian nuclear power program could provide a convenient rationale for the acquisition of special fissile material and related technologies for nuclear weapons production. To avoid this possibility, an international safeguard regime was established by Non-Proliferation Treaty (NPT) agreements and enforced by the International Atomic Energy Agency (IAEA).

Reactors, enrichment, reprocessing, and other nuclear facilities in states without nuclear weapons are internationally safeguarded in order to detect and deter the production or diversion of weapons-grade fissile material.

De jure Non-Proliferation Treaty/nuclear-weapons states (United States, United Kingdom, France, Russia, and China), however, have more often than not regarded this regime with skepticism. They are not fully confident that safeguards could detect illegal actions in a timely manner. The prevailing view has been that mere possession of sensitive technologies elevates a state without nuclear weapons to a de facto nuclear-weapons-state status.

The possibility that a nuclear device might be made rapidly leads prudent adversaries to act as if the weapon already has been made. Nevertheless, from a technical point of view, special-fissile-material acquisition constitutes only a first step for those procuring an explosive device– the further steps also are submitted to other international safeguard regimes, such as the Missile Technology Control Regime (MTCR).

Today, the fears about the spread of nuclear power—potentially leading to a “horizontal” nuclear weapons proliferation—have not been realized. Mainly owing to concerns about reactor safety, slow economic growth, and the high costs of the required infrastructure and reactor construction, nuclear power has hardly diffused beyond those states where it already existed in the 2000’s. The focus of proliferation concerns has been on the efforts of some countries to develop a nuclear-weapons capability.

The supposed—or publicly assumed—plans of several non-nuclear-weapons states to acquire nuclear attack submarines (such as Brazil, beginning in the 1980s) have heated up the proliferation debate.

Historically, the development of nuclear reactors for naval propulsion in nuclear weapons states preceded their use as power sources for civilian applications. For instance, the commercial pressurized water reactor is a direct descendant of submarine reactors developed for the U.S. Navy in the early 1950s. In the case of the United States, nuclear propulsion was developed after nuclear-weapons acquisition.

A Peaceful Application of Nuclear Energy?

There was a difference between IAEA and Non-Proliferation-Treaty safeguard approaches: the former stated that nuclear energy should not be used for “not-well-defined” military purposes, while the latter insisted that nuclear energy should not be used for “well-defined” explosive warfare purposes. In the past, this led to some ambiguous interpretations, which have since been clarified.

According to IAEA statute the agency shall ensure—so far as it is able —that assistance provided by it, or at its request or under its supervision or control, is not used in such a way as to further any military purpose.[i] This provision implies, for example, that safeguards would be designed to ensure that enriched uranium supplied for use in a civilian power reactor would not be used in nuclear weapons or in non-explosive military applications such as naval propulsion or military satellites.

In contrast, Non-Proliferation Treaty agreements prohibit the diversion of nuclear material from “peaceful activities” to “weapons or other explosive devices,” but do not include any prohibition on “non-explosive military applications.” These agreements include provisions that allow a state to withdraw nuclear material from general safeguards while it is being used for a “non-proscribed military activity,” such as fuel for a submarine propulsion reactor.[ii]

To harmonize these originally different approaches, the actual IAEA safeguard agreements[iii] incorporate the Non-Proliferation Treaty principles, including provisions to withdraw from general safeguards materials to be used in “non-proscribed military activities,” such as nuclear submarine propulsion.

The official IAEA opinion—in response to an Argentinean representative on the Board of Governors request arising from the presence of a British nuclear attack submarine in the South Atlantic during the Malvinas /Falklands War is extremely relevant.

It directly questioned the degree of compatibility among the Treaty for the Prohibition of Nuclear Weapons (NPT) in Latin America and the Caribbean, the safeguards agreements in force, and the IAEA statute referring to the legitimacy of non-explosive military applications of nuclear materials.

The IAEA report established that the differences among the various types of agreements do not convey any incompatibility.[iv] It is reasonable to say that nuclear submarine propulsion is compatible with a nuclear program exclusively directed to peaceful ends—such as Brazil’s program.

A Deception for Nuclear Weapons?

The technological capabilities acquired while developing nuclear attack submarine could theoretically facilitate the future acquisition of nuclear weapons. These capabilities, however, also facilitate social and economic growth. Obviously, the potential spin-off effects arising from a nuclear-propulsion program go well beyond just weapons applications.

There is no doubt that the development of nuclear-fission technology enhances the potential capacity of a country to produce nuclear weapons. To make them, however, is a political decision. An example of strong political will against such weapons is Brazil, whose Federal Constitution unambiguously bans nuclear weapons from its national territory.

In 1991, Brazil and Argentina signed the so-called Bipartite Treaty to safeguard their indigenous nuclear facilities, creating an independent agency for nuclear material inventory control called ABACC. IAEA was then invited to participate fully in this particular safeguard regime, and the so-called Quadripartite Treaty was signed in the same year—and is currently being enforced.[v]

This treaty defines specific provisions for the use of materials produced by safeguarded facilities in nuclear propulsion. In this case, their “special procedures” assure safeguard enforcement above and beyond the safeguards imposed by IAEA, without disclosing technological or military classified information on nuclear attack submarine design and operation.

The proliferation of nuclear weapons is an eminently political and non-technical subject. Both de jure and de facto nuclear-weapons states obtained fissile material through programs specifically directed to that purpose.

Consequently, they have followed the shortest and economic way toward the objective pursued, and it is highly unlikely that a country procuring nuclear weapons capability would choose such an indirect route as the development of nuclear naval propulsion.

It is to be noted that, not adhering to NPT, Indian Navy developed nuclear-powered and nuclear-armed ballistic missile submarines, after developed nuclear weapons: the Arihant class. This was the first nuclear submarine to be built by a country other than the five permanent members of the United Nations Security Council.

It is to be noted too that Israel, also not adhering to NPT, developed, with German partnership, the Dolphin class, a conventionally-powered and nuclear armed submarine. The same is supposed to be done by North Korea.

A “Proliferant” Fuel Cycle?

Even though not proscribed by the Non-Proliferation Treaty, naval propulsion is undoubtedly a military application of reactor technology. This might lead some to conclude there is a major difference between the fuel cycles of nuclear submarines and stationary power or research reactors, and that international and/or multilateral safeguards would have difficulty in deterring the diversion of nuclear materials from a submarine’s fuel cycle.

Technically, this is not the case at all. Owing to constraints on space in a submarine and the operational requirement for infrequent refueling, submarine reactors do use uranium fuel in an enrichment higher than stationary reactors (current U.S. submarine reactors even are said to use weapons-grade highly enriched uranium). On the other hand, France developed an alternative low-enrichment uranium fuel technology in the 1970s, and there are indications that Russia may not use high-enrichment uranium fuel neither.

Presently, naval propulsion reactors are compact pressurized water types. Fuel enrichment is not necessarily “weapons grade,” nor is this kind of reactor suitable for plutonium production. A naval propulsion reactor is exactly the same as many of the research and power reactors that are operating throughout the world-without anyone claiming they may represent a possible violation of the status quo.

Regarding this aspect, a new problem arises from AUKUS Agreement. The specific type of nuclear fuel for the AUKUS submarines has not been announced yet. However, it is expected that they will use highly enriched uranium as US and UK submarines. This poses questions about in what extent the NPT obligations of US and UK, as nuclear weapon states, and Australia, as a non-nuclear weapon state, are fully respected.

A Rationale for Regional Nuclear Weapons Races?

Considering its capital value for naval power, nuclear attack submarine acquisition by a non-nuclear weapons state could induce nuclear weapons proliferation in other countries that feel threatened by such change in their regional naval balance of power. Nuclear propulsion is a part of a conventional weapon system, however, and a more appropriate response would be to develop their own nuclear submarines. By this same rationale, the introduction of any totally non-nuclear weapon system could alter the balance of power.

There is a widespread consensus among strategists that future naval warfare will rely heavily on submarines—particularly the nuclear attack submarine—rather than on surface ships. This view is corroborated by the continuing development of increasingly sophisticated submarines in the West and Russia. This provides a strong incentive for nuclear submarine acquisition by militarily significant Third World countries.

To the extent that nuclear attack submarines could serve as surrogates for nuclear weapons, they may promote international stability: “Better a sub under the sea than a bomb in the basement.” On the other hand, their acquisition might spur naval weapons races among regional rivals with no net gain in national or international security.

Nuclear-weapons states cannot hope to minimize this trend by “advocating water and drinking wine.” Rather, they should follow their own example given in the case of nuclear weapons “vertical” proliferation reduction – by decreasing the reliance on nuclear attack submarines.


Even if potential nuclear attack submarine-related proliferation risks are not to be discarded, they should not be exaggerated. The emphasis on non-proliferation was largely based on the expectation that nuclear power would spread rapidly after the 1973 oil crisis.

That prediction did not become a reality. For similar reasons, such as high research, development, construction, and maintenance costs, technological risks, and stringent fissile-material supply conditions, the number of Third World states acquiring nuclear submarines will remain small, Brasil, South Korea, Australia and perhaps Iran being the most referenced as potential newcomers. Consequently, it is time to develop an internationally recognized policy toward these acquisitions regarding proliferation.

The emergence of a new class of “nuclear-submarine state” would tend to reduce both the psychological and the military distinctions between nuclear and non-nuclear-weapons states created by the Non-Proliferation Treaty.

As in the case of nuclear-weapons proliferation, the degree of opposition to such a development depends on the identity of the nuclear-submarine state. The United States is strongly opposed to any new nuclear-submarine states—because it might limit the U.S. Navy’s freedom of action around the world.

On the other hand, both the United Kingdom and France encouraged Canada’s nuclear-submarine ambitions—but presumably they would oppose Latin American ones. Russia leased twice a nuclear guided-missile submarine to India and probably also assisted the Indian domestic nuclear-submarine program-despite strong opposition from the United States.

By other side, China presumably would be extremely opposed to eventual nuclear submarine acquisition by an East or Southeast Asian country, as Australia—but not to others.

The stringent restraints on the supply of fissile materials and the political pressure exerted to prevent the indigenous development of nuclear attack submarines in Non-Proliferation Treaty/non-nuclear-weapons states in the Third World are fundamentally based on geopolitical and military strategic objectives. This practice is hardly related to the Non-Proliferation Treaty spirit; it is, in fact, a matter of freedom of the seas—not nuclear proliferation.

*Leonam dos Santos Guimarães is a nuclear and naval engineer (PhD) and a member of the Brazilian National Academy of Engineering. He was CEO of Electronuclear SA and Coordinator of the Nuclear Propulsion Program at the Naval Technology Center in São Paulo. He is currently Coordinator of the Statutory Committee for Angra 3 Nuclear Power Plant construction and commissioning. [IDN-InDepthNews]

Photo: Dolphin Class Submarine. Credit:Thyssen Krupp

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[i] IAEA statute, Article III.

[ii] Non-Proliferation Treaty Article IV.

[iii] IAEA INFCIRC/153, Paragraph 14.

[iv] IAEA Report GOV/INF/433.

[v] Brazil adhered to the Non-Proliferation Treaty in 1998, Argentina some years before that.

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