Iran's new quest for nuclear submarines: dangerous and needless

After a recent announcement by the deputy chief of the Iranian navy that it is considering nuclear propulsion for its submarines, actions have proceeded swiftly. A bill an Iranian Parliament (Majlis) committee was approved, and debate has followed, parallel to the latest round of P5+1 talks with Iran in Istanbul, which concluded last week.

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. There is speculation that nuclear propulsion will be used as a bargaining chip to trade away in international talks 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.

Nuclear powered vessels were not mentioned in the paper distributed by Iran at the recent Moscow and Istanbul talks. (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 International Atomic Energy Agency.

Nuclear-powered vessels around the world

Since the 1940s, 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 1980s to acquire such vessels to guard its vast Arctic waterways, but gave them up not least for cost reasons.

Traditionally, fuel for naval reactors uses highly enriched uranium to reduce reactor size. For example, American submarines use highly enriched uranium fuel of up to 97 percent enrichment and fuel for Russian icebreakers is enriched up to 75 percent.

There have been some exceptions. Low-enriched uranium fuel has been introduced in submarines in France. The “caramel” low-enriched uranium fuel used in French submarines is known to be around 7.5 percent enriched, which enables enrichment and manufacturing at its civilian plants. Brazil’s planned nuclear submarine is also expected to use low-enriched uranium fuel. Merchant ships such as the USS Savannah (US), Otto Hahn (Germany), and Mutsu (Japan) used low-enriched uranium 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. Built to withstand a rough sea environment, long refueling intervals, and compact in size, naval reactors are built to much more rigorous standards than other pressurized water reactors. 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 thermal megawatts and smaller ones about 50 thermal megawatts.

The case of Iran

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 percent highly enriched uranium or 100 kg of 45 percent highly enriched uranium to power a small submarine. The highly enriched uranium produced under the first scenario is equivalent to the amount needed for two 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 highly enriched uranium amounts equal to half a dozen nuclear weapons.

Should Iran proceed to design and construct a reactor for oil tankers or liquid-natural-gas 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 as models, 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. Highly enriched uranium fuel for the naval program could be diverted for other purposes. This is also the case for low-enriched uranium produced, as it could be diverted 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 Iranian officials point to the direction of Iran using highly enriched uranium as a future 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 liquid natural gas tankers 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 Iran intends to develop nuclear-powered submarines, it is difficult to justify, with the limited feasibility and greater financial sanctions that would result from 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.

Olli Heinonen, a senior fellow at Harvard Kennedy School’s Belfer Center for Science and International Affairs, is a former deputy director general of the International Atomic Energy Agency, where he headed its Department of Safeguards.

A version of this piece first appeared on the Power & Policy blog at Harvard Kennedy School’s Belfer Center for Science and International Affairs.