Reprinted with the permission of Radio Free Europe/Radio Liberty, PRAGUE: Iran's President Mahmud Ahmadinejad on August 26 inaugurated a heavy-water plant that is to provide fuel for a heavy-water nuclear reactor, which Iran hopes to finish by 2009.
How do the two projects tie into Iran's overall nuclear program and does it all mean Iran is edging closer to making a nuclear bomb? RFE/RL correspondent Jeremy Bransten spoke with British nuclear physicist Frank Barnaby, who explains the science of Tehran's nuclear programs.
On July 31, the UN Security Council passed a resolution calling on Iran to halt its uranium-enrichment activities within a month or face possible sanctions.
The document also incorporated language from an earlier International Atomic Energy Agency (IAEA) resolution, which urged Iran to halt its heavy-water project at Arak, as a confidence-building measure. But that was not made a requirement.
Now, it appears Iran is a step closer to building its heavy-water facility. Heavy-water reactors are known by that name because they use so-called “heavy water,” which contains deuterium. This is a modified form of hydrogen that has more neutrons in its nucleus, making it literally “heavier.”
Most nuclear power plants have so-called light-water reactors, which require enriched uranium to fuel them.
But the advantage of heavy-water reactors is that they can use unrefined natural uranium as fuel and uranium can be mined in Iran. Plutonium, which can be used to make nuclear weapons, emerges as a by-product from both heavy-water and light-water reactors.
RFE/RL: Dr. Barnaby, what do we know about the facility Iran is building?
Frank Barnaby: It's a small reactor that is designed to replace another reactor, which is at the end of its life. And they say that that's used to produce radioisotopes for medicine and industry. And that may well be true. But [the reactor] also could effectively produce plutonium, as a by-product. It could produce enough plutonium, in theory, to produce a couple of nuclear weapons per year. So it is certainly an element in a nuclear-weapon program, if that is what is happening there.
RFE/RL: Can you explain the science behind how plutonium is produced in a nuclear reactor? And can that plutonium be used for nuclear weapons?
Barnaby: A reactor produces plutonium in the fuel element. The fuel that you put into the reactor, inevitably — after a time when it's been running — produces plutonium. That is unavoidable. But you then have to take that fuel element, with the plutonium in it, and chemically separate the plutonium from the unused uranium fuel and from the fission product. So you have to separate these three things. And you do that in a chemical plant. Once you've got the plutonium out, then you can use it to produce a nuclear weapon.
Enriched Uranium Or Plutonium
RFE/RL: If you were pursuing a nuclear-weapons program, would you concentrate on manufacturing highly enriched uranium or plutonium?
Barnaby: If you had a choice to make a nuclear weapon from highly enriched uranium or plutonium, you would choose plutonium, for a number of reasons. Firstly, you need much less. If you're a reasonable nuclear-weapon designer, you can make a nuclear weapon using 3.5 or 4 kilograms of plutonium. But you need about 20 kilograms of highly enriched uranium. And there's a massive difference there.
And also, of course, the nuclear weapon itself — using plutonium — would be smaller in size and weight. And that's important because of the need to miniaturize nuclear weapons in order to deliver them as warheads on missiles. So, the plutonium route is far more attractive than the highly-enriched-uranium route.
RFE/RL: Isn't that, in fact, what Israel did to develop the nuclear arsenal it is widely believed to have?
Barnaby: Israel used the heavy-water-reactor route, a small reactor like the one Iran is planning, for its nuclear-weapon force. There's a bit of an irony there.
RFE/RL: Are there any countries with nuclear weapons that have used the uranium-enrichment route?
Barnaby: As far as we know, the only country in the world using highly enriched uranium, in preference, is Pakistan. And it's doing it that way because A. Q. Khan, the leader of the Pakistani nuclear-weapon program, learned how to make highly enriched uranium when he worked at URENCO, the highly-enriched-uranium-production plant in Europe. So there's a special reason there. But even the Pakistanis are now going into plutonium production.
Matter Of Scale
RFE/RL: If that's the case, then why are the UN, media, and world politicians so focused on Iran's uranium-enrichment program — and not so much on the heavy-water project?
Barnaby: The heavy-water reactor, if used to produce plutonium for weapons, could produce at most enough for a couple of weapons per year, under the best conditions. What the IAEA and other people are afraid of, is that the Iranians will build a very large gas-centrifuge plant that can produce enough highly enriched uranium for a much, much larger number of nuclear weapons.
It's the scale of the thing. The heavy-water research reactor would be on a very small scale. People are afraid that Iran will eventually have a very large, highly-enriched-uranium plant to produce nuclear weapons on a large scale, if you follow me. So it's the scale of the operation which is the thing that concerns people.
RFE/RL: It seems few people these days mention the light-water nuclear reactor at Bushehr that the Russians are building. Does that still pose a potential military threat?
Barnaby: The large light-water reactor that the Russian are building in Bushehr in Iran also [will] produce, inevitably, [small amounts of] plutonium. And that plutonium could be used in nuclear weapons. So in addition to highly enriched uranium, Iran has these two [potential] sources of plutonium — one is the heavy-water research reactor or isotope-producing reactor and the other is the light-water reactor that is to be used for electricity production being constructed by the Russians at Bushehr. So to concentrate on highly enriched uranium is in a sense misleading.
RFE/RL: But it will take quite a while to accomplish that, right? What's your best assessment?
Barnaby: If the Iranians stop at producing nuclear fuel for their reactor — in other words uranium enriched at 3 percent or 4 percent — then no one will be very concerned about that. They're entitled to do it and it has no weapon implication. It's only if they go to a much higher enrichment of that uranium that people will worry. And that's many years down the line. Whichever route they use, they're a decade away from nuclear weapons, probably.
Value Of Diversification
RFE/RL: But Iran, from a strategic standpoint, appears to be in an enviable position. They've diversified their nuclear program as much as possible, in a pretty smart way. Would that be a fair assessment?
Barnaby: Yes, you could even say that. You can say that if they are heading for nuclear weapons, they've made sure they have all the elements of the nuclear fuel cycle on their territory, certainly.
RFE/RL: So should the world be worried?
Barnaby: If you make an assumption that Iran is going for nuclear weapons, if you assume that, then all three are of concern. You wouldn't want them enriching uranium, you wouldn't want them using a heavy-water reactor, and you wouldn't want them to be able to use plutonium from their light-water reactor.
