Jeffrey LewisHeavy Water Plant Not Nuclear Reactor

I was annoyed that most of the major news outlets incorrectly described Iran’s heavy water plant (which cannot make plutonium) as a nuclear “reactor” (which can).

I was thinking that an excellent blog post would point out that a heavy water plant separates separates heavy water from regular water by distillation, electrolysis or various chemical processes; that heavy water contains deuterium which makes an excellent moderator in a nuclear reactor, and that a heavy water plant DOES NOT MAKE PLUTONIUM.

Then Cheryl Rofer wrote that, and more, at Whirledview

Here are the differences: the heavy water plant produces (distills, most likely) heavy water from regular water. Heavy water contains deuterium, which is an isotope of hydrogen that has more neutrons in its nucleus, which makes it more effective at slowing down reactor neutrons to produce a chain reaction. An enrichment plant raises the amount of uranium-235, the fissionable isotope of uranium, from its natural abundance of 0.7% to reactor grade (about 3%) or weapons grade (greater than 90%). A reactor brings the uranium and heavy water together to produce a controlled nuclear chain reaction, which can be used to produce power and plutonium, another weapons material. The heavy water plant has no radioactivity involved, the uranium in the enrichment process is slightly radioactive, and a reactor is very radioactive.

Oh, and to all those reporters smart enough to understand the D20 would be used in a nuclear reactor, but thought it was only as a coolant … no, you don’t get a cookie for being half right.

Jack Boureston has an interesting discussion about the specifications of the IR 40—the heavy water reactor under construction at Arak, if you, unlike the press, actually care about the details.

Steven Dolley with Platts points out that my comment about the “press” was too sweeping.


  1. Captain_Canuck

    “Reports who smart enough”…uh oh, better edit that one quick!

  2. Pavel

    I’m not sure that deuterium is “more effective at slowing down reactor neutrons”. If my memory serves me right, since deuterium is heavier than hydrogen, it’s probably less effective. The point in using heavy water is not it’s properties as a moderator, it is that it does not absorb as many neutrons as regular water, making it possible to use natural uranium as a fuel. Given all the brouhaha around Iran’s enrichment program, this is not a small detail.

  3. yale

    In a way, describing the heavy water as needed to cool the reactor is actually more than just half right.

    The d2o removes reaction heat from the reactor and it ‘moderates” the neutrons. What is ‘moderation”? It is cooling down the neutrons
    so that they are more easily captured by the uranium nuclei. This temperature lowering is called thermalizing the neutrons.

    Bottom line, in principle, those reporters completely inadvertantly got it right!

  4. Andy (History)

    Sadly, I’ve also seen a few bloggers claim the deuterium from the plant will be used in Iranian fusion bombs.

  5. Doug Gardner (History)

    These news reports are so flawed that I don’t believe all reporters are stupid. I think they are mimicing the admistration and purposely trying to deceive.

  6. Max Postman (History)

    The opening sentence of Boureston’s article: “Iran has admitted that it is in the final phase of designing a 40MW heavy water nuclear reactor at Arak.”

    Am I missing something, or is he contradicting your edict against calling the heavy water plant a “nuclear reactor.”?

  7. Pete

    Uh, Cheryl really confuses me. I thought Iran produced heavy water for use in the far from finished IR40 to produce industrial and medical isotopes (and who knows, may be a bit of plutonium on the side) from natural uranium. No enrichment needed…
    And on the other hand no heavy water needed for a light water reactor like the Busherh one, which does use low enriched uranium.
    Do I get a cookie now?

  8. Jeffrey Lewis

    Pavel: Well right, I think they way I learned it is that it slows rather than captures, hence my phrase that “deuterium … makes an excellent moderator in a nuclear reactor…”

    Pete: Cookie indeed. I have been baffled about why the Bush Administration doesn’t make a bigger deal out of the IR 40 at Arak, which I would not let become operational.

  9. yale

    d2o is useful for both reasons.

    deuterium captures only 1/650th as many neutrons as
    hydrogen, and it is more than 70% as effective in slowing down the neutrons (which is a cooling process) as hydrogen.

    Hence you have the perfect combination of copious neutrons at the right temperature to breed Pu from U238.

    Another weapon-making advantage is it allows the use of widely spaced fuel rods, which aids in designing online refueling.

    Except for its relatively high cost, it is an almost ideal moderator.

  10. Steven Dolley

    Let’s not broadbrush “the press” as ignorant of this very important distinction, just because the New York Times, for some reason, happened to assign a human-interest reporter to cover a technical issue. Many of us are on top of it.

  11. Derek

    As of yet there is no indcation that Iran is building the reprocessing plant required to extract the plutonium from the Arak reactor’s fuel. How difficult is such technology to master and/or acquire? Any estimates on the time lines for building such a facility? If Arak is scheduled to come on line in 2009 (how realistic is that claim as it was originally supposed to be in 2014?) when would Iran need to begin constructing a reprocessing plant? Indications that Iran was constucting a facility capable of such reprocessing would be an important indicator of Iran’s ultimate intentions.


  12. madamab

    The press is completely pathetic on this and every other issue. Just witness the ridiculous feeding frenzy occasioned by the extradition of a possible suspect in a 10-year-old murder case. As anyone who was paying attention could have told them, Karr’s family said from the very beginning that he was not even in Colorado at the time and thus could not have been the killer. Yet all other “news” ceased and the media acted as if Karr were tried, convicted and sentenced.

    As for Derek’s remark, it is right on target. The earliest estimates I have seen regarding Iran’s ability to actually create a nuclear weapon, have been 5-10 years. Nothing has occurred recently to change that estimation; it’s just more media hype and hysteria designed to terrify the public and justify invading Iran.

  13. Andy (History)

    Time estimations on development programs like this are tricky business, which is why there are such varied viewpoints. Even with good intelligence on the current state of a program, many assumptions are required to make a future estimate. My personal feeling is around 5 years, but places like Lavizan worry me.


    I think the estimate was reduced based on when the Iranians would have enough heavy water for the reactor. It seems like work is proceeding briskly.

    I, too, am curious about the apparent lack of concern about the Arak reactor, which is a must bigger threat than enrichment, imo.

  14. Jason (History)
  15. BobM (History)

    I read the link re: the specs. of the IR-40 that was recommended. They indicated the plant is a “heavy water reactor” and not just a heavy water plant. What did I miss?

  16. Jeffrey Lewis

    The IR 40 is the reactor, which is not yet operational.

    What Ahmadinejad opened was the heavy water plant.

  17. miles (History)

    Presumably you mean “reactor” in your headline…

  18. Derek

    While the Arak reactor is certainly a proliferation concern, care should be taken not to exaggerate its potential. If Iran remains within the NPT, certainly an important if, it would be difficult for Iran to divert significant quantities of fissle material from Arak’s core when it is periodcially refuelled. It cannot be operated covertly and produces a “relatively” small quanitity of Pu per year. Iran’s centrifuge program is a far differenct animal. Should Iran acquire the capability to indigenously produce centrifuges not only could it build cascades capable of producing far larger quanities of weapons grade material (Natanz with multiple thousands of cascades)than Arak, it could do so covertly at multiple sites. Iran’s emerging centrifuge technology because of its scalability, flexibility, and inherent capability of being decentralized is a greater proliferation threat than a single small heavy water research reactor.

  19. CKR (History)

    Steven Dolley says:
    “Let’s not broadbrush ‘the press’ as ignorant of this very important distinction, just because the New York Times, for some reason, happened to assign a human-interest reporter to cover a technical issue. Many of us are on top of it.”

    But you’re not on top of how the story appeared. It was an AP story with a totally incorrect headline and errors in the body. The NYT, WaPo, and Boston Globe all printed it just exactly like AP shipped it to them. Not a murmur that the headline conflicted with the body of the article, something that even an editor with no science knowledge whatsoever should have picked up.

    WaPo kept it at the top of their electronic front page most of the day. NYT replaced it in a few hours with a somewhat improved article (but still no cookie) by one of their own reporters.

    That’s a pretty important slice of the press. Would they have printed an article this incorrect about Tom Cruise?

  20. Georg Schoefbaenker (History)

    Today (Aug 30) again in CSM: the “reactor”. It has method. How many not scientifically educated people can really distinguish between a D2O plant and D2O reactor? I guess it converges to zero. So let’s expect more of this and drumbeats of war.

    In the days leading up to the ultimatum, Iran’s leaders have fired a broadside of defiant statements. Iran’s predictably provocative president, Mahmoud Ahmadinejad, pointedly inaugurated a new heavy-water reactor over the weekend as a rebuff to those who want his country to stop its uranium processing.

    Mr. Ahmadinejad says the reactor will be used only for peaceful purposes. Given Iran’s long record of duplicity about its nuclear ambitions, Western European nations and the US believe it will be used to produce nuclear weapons.

  21. bjr

    At 0:12: “Just a few days ago president Mahmoud Ahmadinejad inaugurated a heavy water production plant which is capable of producing weapons grade plutonium.” Sigh.

    At 1:32: “this weeks inauguration of a heavy water nuclear reactor.” Double sigh.

  22. hass (History)

    Back to the enrichment issue: it should be mentioned that Argentina has announced plans to start enrichment, as has South Africa (recently announced by SA Minister of Energy and Mineral affairs, Buyelwa Sonjica)

  23. CKR (History)

    Both Chris Wallace on the Sunday morning Fox News talking head program and Margaret Warner, on Monday night’s News Hour, referred to the “reactor, um, heavy water plant.”

    Interesting that they got it wrong first, then corrected themselves. They (or somebody) wrote a script, but that wasn’t enough to keep them from saying the r-word?

  24. Mark Gubrud (History)

    Why hasn’t the Bush camorra made more of the Arak reactor project?

    Strategic depth, in case the uranium issue is unexpectedly resolved.

  25. Derek

    Has anyone posted the latest IAEA report on Iran yet? Its been leaked to the AP, but none of the usual suspects seem to have posted it yet.

  26. Steven Dolley

    “But you’re not on top of how the story appeared. It was an AP story with a totally incorrect headline and errors in the body.”

    It’s best not to be condescending when you don’t have the facts straight.

    What I saw, and cited in my earlier post, was not an AP story, but an August 27 NYT story by Michael Slackman, who is a NYT reporter.

    In that story, both the headline and the lead were wrong (see below).

    New York Times
    August 27, 2006

    Iran Opens a Heavy-Water Reactor


    TEHRAN, Aug. 26 — Just days before it is supposed to suspend enrichment of uranium or face the prospect of sanctions, Iran continues to project an image of defiance and confidence. Its position regarding the demand that it suspend enrichment remains a determined “no.”

    On Saturday, President Mahmoud Ahmadinejad made a provocative, if symbolic, gesture by formally inaugurating a heavy-water reactor. The Iranians say the plant would be used for peaceful power generation. But nuclear experts note that heavy-water facilities are more useful for weapons because they produce lots of plutonium — the preferred ingredient for missile warheads.

    Even the NYT August 31 correction is confusing. They should have said “heavy water PRODUCTION plant,” because reactors are often referred to as “plants.”
    Correction: Aug. 31, 2006

    Because of an editing error, an article and headline on Sunday about Iran’s nuclear program referred incorrectly in some copies to a facility that the Iranian president inaugurated. It was a heavy-water plant, not a reactor.

  27. Jeffrey Lewis

    Quite apart from the merits of the claims being debated, I’d like to remind folks to keep it civil—I am the only person who gets to be a dick on my blog.

    No one is over the line — yet. But I think we are edging in that direction.