Iran's New Quest for Nuclear Submarines: Dangerous and Needless

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Iran recently announced plans to develop nuclear-powered submarines, requiring enough highly enriched uranium for two nuclear weapons. Tehran's ambition seems to be more than just a bargaining chip. Upping the ante on its questionable nuclear program is 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. …