Analysis & Opinions - Belfer Center for Science and International Affairs, Harvard Kennedy School Power & Policy Blog

Nuclear Submarine Program Surfaces in Iran

| July 23, 2012

After the announcement by the deputy chief of the Iranian navy that it is considering nuclear propulsion for its submarines[1], actions have proceeded swiftly. A bill in the Iranian Parliament (Majlis) Committee was approved[2], and debate in Majlis is to follow in coming days, parallel to the next round of the P5+1 talks with Iran in Istanbul.

The Majlis debate brought to the arena additional aspects of the Iranian plans: the use of nuclear propulsion for oil tankers and possible use of uranium with higher enrichment[3]. There is speculation that nuclear propulsion will be used as a bargaining chip to trade away or as (eventual) justification for continuing uranium enrichment and get to higher enrichment. Some have raised questions about Iran’s proclamations and its actual capacity to develop nuclear submarines. At the on-going negotiating track, the issue of nuclear powered vessels was not mentioned in the paper distributed by Iran at the recent Moscow and Istanbul talks[4]. (What else is in the pipeline that has not been mentioned?)

The issue gets more complicated, since non-nuclear-weapon states are allowed to remove from IAEA safeguards nuclear material intended for non-proscribed military use, such as fuel for nuclear submarines, under arrangements to be agreed with the IAEA[5].

Since the 1940’s, about 500 vessels with nuclear propulsion have been built. Most are nuclear powered submarines that belong to nuclear weapons states. The majority of nuclear powered vessels at sea are also military, such as aircraft carriers. Only a few countries have constructed merchant vessels with nuclear reactors. Most of the civilian nuclear vessels are in Russia, which uses nuclear powered icebreakers in the Arctic regions. Currently Brazil and Argentina are the only non-nuclear weapons states with plans to build nuclear powered submarines. Canada had plans in the 1980’s to acquire such vessels to guard its vast Arctic waterways, but gave them up not least for cost reasons[6].

Traditionally, fuel for naval reactors use highly enriched uranium (HEU) to reduce reactor size. For example, American submarines use HEU fuel of up to 97 % and Russian icebreakers’ are up to 75 %. There have been some exceptions. Low enriched uranium (LEU) fuel has been introduced in submarines in France. The “caramel” LEU fuel used in French submarines is known to be around 7.5 %, which enables enrichment and manufacturing at its civilian plants. Brazil’s planned nuclear submarine is also foreseen to use LEU fuel. Merchant ships such as the USS Savannah (US), Otto Hahn (Germany), and Mutsu (Japan) used LEU fuel, but they no longer exist.

Nuclear reactors in vessels are also complex, costly and varied. The design of submarine and surface vessel reactors differ from each other. With a few exceptions, naval reactors have been pressurized water reactors (PWRs). Built to withstand a rough sea environment, long refueling intervals, and compact in size, naval reactors are being built to much more rigorous standards than other PWRs. Due to design constraints, only one third of the energy produced is used for propulsion. The sizes of reactors also vary, the largest being 200 MWt and smaller ones about 50 MWt.

So what should we be looking out for in the case of Iran?

If we put aside for a moment the question of if, whether, and when Iran will make good on its proclaimed intent, this is what it could mean in terms of enrichment for Iran. Iran would need to produce approximately 50 kg of 90 % HEU or 100 kg of 45 % HEU to power a (small) 50 MWt submarine. The HEU produced under the first scenario is equivalent to the amount needed for 2 nuclear weapons. But before that, a land-based test reactor of the same scale would need to be constructed. In sum, with those two reactors and additional materials needed for testing and manufacturing, such a project would require HEU amounts equal to half a dozen nuclear weapons. Should Iran proceed to design and construct a reactor for oil tankers or liquid natural gas (LNG) tanker, the power of the reactor would be double. The suggested Iranian plan would mean the design of two different types of reactors; one for submarines and another one for merchant vessels. If we use the Canadian and Brazilian experiences such projects would likely costs billions of dollars, and will likely require foreign assistance and know-how.

Apart from the required substantial costliness and effort poured into such an exercise, an additional problem in verification arises. Diversion of nuclear material is not only an issue for HEU fuel for the naval program but also for the case of LEU produced, as plausible feedstock for high enrichment to an undeclared/unknown facility.

The recent Iranian paper distributed in the Istanbul technical meetings does not mention naval needs. Yet the matter is being taken up at the Majlis, and some statements made by officials points to the direction of HEU foreseen as a fuel. The IAEA safeguards agreement provides an option to exempt finished submarine or other military fuel from safeguards, but fuel for the oil tankers or LNG would remain under IAEA control.

With a nuclear program that has generated international concern over its purely peaceful nature, an Iranian move in the direction of upping the ante with nuclear powered vessels is both dangerous and needless.

Diplomacy powered with sanctions has brought Iran back to the negotiating table with the P5+1. If nuclear powered vessels are being used as leverage, it would likely result in even more pressures brought to bear on Iran. If it is intended as a next step toward a national aspiration, it is difficult to justify with the limited feasibility and greater financial privations that would result over such a difficult and costly exercise. Yet, the naval propulsion program debate in the Majlis could not have come to this stage without a tacit approval of the leadership, which means that this may not be just a bargaining chip given easily away.

[1] Press TV, Iran to Build Nuclear-power Submarines: Commander, 12 June 2012.

[2] AP, Iran Reinforces Nuclear Rights, OKs Atomic Merchant Ships, 16 July 2012.

[3] Mehr News Agency, Iran needs 50-60% enriched uranium to power commercial ships: MP, 20 July 2012.

[4] Mehr News Agency, Details of Iran’s views presented at 5+1 talks released,7 July 2012.

[5] The Structure and Content of Agreements between the Agency and States Required in Connection with the Treaty on the Non-proliferation of Nuclear Weapons, Paragraph 14, INFCIRC/153 (Corrected), IAEA.

[6] A. Lajeunesse, Sovereignity, Security and the Canadian Submarine Program, Canadian Military Journal, Winter 2007-2008, p. 74-82.

This op-ed was also published by The Christian Science Monitor :


For more information on this publication: Belfer Communications Office
For Academic Citation: Heinonen, Olli.“Nuclear Submarine Program Surfaces in Iran.” Power & Policy Blog, July 23, 2012.

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