Arms Control Wonk

The most recent edition of Survival has a section on “Reinforcing the NPT”. One of the articles, “The Problem with Nuclear Mind Reading”, is by me (non-printable proof available here), and the other, entitled “Exposing Nuclear Non-Compliance”, is by former IAEA Deputy Director General for Safeguards, Pierre Goldschmidt (available for free here).

My article asks the question: Should we care why a non-compliant state has violated its non-proliferation undertakings, or instead focus on what it has done? My answer is that we should focus on actions not intentions—not least because the IAEA is not tasked with assessing intentions and it would be effectively impossible for it to do so.

If the topic sounds familiar to Wonk readers it probably is. The article grew out of my first ever posting on this blog and has been the subject of a few since then. [And was the subject of a talk James gave at the New America Foundation, which you can view on YouTube. — Jeffrey]

Anyway, like every other idea in non-proliferation, it turns out not to be so new. Its origin? The Acheson-Lilienthal Report. Where else? (The creators of South Park captured the feeling nicely in this episode, to which the title of this post is a tribute).

I was rereading A-L the other day, which as many of you will know, proposes international control of the fuel cycle (or rather, “dangerous” activities) by an Atomic Development Authority. The following passage described the inspection function of this body:

…the Authority will be aided in the detection of illegal operations by the fact that it is not the motive but the operation which is illegal. Any national or private effort to mine uranium will be illegal; any such stockpiling of thorium will be illegal; the building of any primary reactor or separation plant will be illegal. This circumstance is of very great importance for the following reason: It is true that a thoroughgoing inspection of all phases of the industry of a nation will in general be an unbearable burden; it is true that a calculated attempt at evasion may, by camouflage or by geographical location, make the specific detection of an illegal operation very much more difficult. But the total effort needed to carry through from the mine to the bomb, a surreptitious program of atomic armament on a scale sufficient to make it a threat or to make it a temptation to evasion, is so vast, and the number of separate difficult undertakings so great, and the special character of many of these undertakings so hard to conceal, that the fact of this effort
should be impossible to hide. The fact that it is the existence of the effort rather then a specific purpose or motive or plan which constitutes an evasion and an unmistakable danger signal is to our minds one of the great advantages of the proposals we have outlined.

A lesson that, in my opinion at least, is still very relevant today.

It’s February so it’s time for the Wonk’s perennial favourite… Miss Atom: the beauty contest for workers in the Russian nuclear industry.

For those of you who are new readers: check out the 2008 and 2007 posts for the backstory.

The Senate, in its attempt to slim down the stimulus bill, has apparently managed to squeeze in a little bit for nukes. A billion dollars, in fact.

In various Senate version of the Bill, including on page 78 of what I believe is the most recent version, the Collins/Nelson* Bill, the following appears:

ATOMIC ENERGY DEFENSE ACTIVITIES

National Nuclear Security Administration

WEAPONS ACTIVITIES

For an additional amount for weapons activities, $1,000,000,000, to remain available until September 30, 2010.

Some stories speak for themselves, I think, so don’t require editorializing.

I’ll just point you in the direction of some of the organizations and blogs that have been covering the story (WAND, Talking Points Memo and ANA) and thank the person that sent me the tip-off.

Oh, and Everett Dirksen’s most famous bon mot really does seem appropriate here: “A billion here and a billion there, and pretty soon you’re talking real money.”

*I don’t think this URL will be stable. The same language appears on page 76 of S 336, for instance.

There is much talk of negotiations with Iran at the moment. But, there are negotiations and there are negotiations…

Therese Delpech, Eli Levite and George Perkovich have identified six questions about how talks with Iran should be conducted. If the Obama administration is serious about pursuing dialogue with Iran (and I think it is) it will need to work through these questions.

I thought it might be interesting to reproduce the questions here so you can mull them over. Once you have finished mulling, check out their answers.

Regardless of whether of not you agree with their answers, I think all should be able to agree that these are important questions and that the way they are answered by the Obama administration could radically affect the nature of any dialogue with Iran.

The questions…

Should the U.S. seek a dialogue with Iran now, or hold back until the Iranian presidential elections?

Should the U.S. approach and seek nuclear talks with Iran alone, or insist [on] conducting nuclear diplomacy in conjunction with the EU-3 plus Russia and China?

If Iran agrees to join talks on the nuclear issue, should the allies put a time limit on progress or leave the nuclear diplomacy open-ended?

Should the U.S. be open to a comprehensive agenda where the nuclear issue does not come necessarily first?

Should the U.S. pursue a dual-track strategy of seeking stronger sanctions against Iran paired with grander offers of cooperation if Iran complies with UNSC resolutions?

Should the U.S. continue to press for Iran to suspend now its fuel-cycle activities?

A milestone for the Wonk yesterday: 10,000 comments submitted from readers!

The 10,000^th comment came from Major Lemon who asked whether Semipalatinsk stills glows in the dark. Something oddly appropriate about that…

So hats off to Jeffrey who started this blog (and whose it still is, after all) but, most of all to you, our readers. I’m sure that all those who have ever blogged here would agree what a great readership you are and what a privilege it is to blog here.

Since my post last week delving into the question of how big the HEU particle found on something North Korean would have to have been for the US to date it to 3.5 years old, I’ve had a number of interesting discussions on the subject—both in the comments section to this blog and elsewhere. Since the subject is topical I wanted to summarize some of the key open questions.

How accurate is mass spectrometry?
Generally, people seemed to buy my mathematical analysis—the issue was whether my estimate for the accuracy of mass spectrometry (the one unknown parameter in my model) was too pessimistic. This is important because, for a given error bar on the particle’s age, the more accurate the measuring device the smaller the particle need be.

Importantly, I am assured by a number of knowledgeable people that the particular mass spectrometry technique I discussed (TIMS) can be made more accurate than in LaMont and Hall’s experiments on which my analysis was based. So, my estimate of the size is almost certainly something of an overestimate—how much of one is unclear. If anyone can point me in the direction of an article about TIMS with enough quantitative data to be useful, I’d be grateful.

Of course, we’re flying blind to some extent since we don’t know what method of mass spectrometry was used. Russell Leslie points out that accelerator mass spectrometry (AMS) is capable of much more accurate measurements than TIMS. Indeed, H. Lime even provides a link to a picture of LLNL’s AMS facility.

They might well be right. The one note of caution I’d sound is that this is exceptionally tricky experimental work and developing an experimental protocol can be a tough, time-consuming job. Having access to AMS technology doesn’t automatically mean it can be applied to this problem without a lot of prior effort—and I just don’t know whether the required effort has yet been applied.

Indeed, Vitaly Fedchenko pointed me in the direction of the IAEA’s Research and Development Programme for Nuclear Verification 2008–2009 which states that

Age-dating of high-enriched uranium (HEU) particles. This is needed to help deduce the origin of HEU particles found in environmental samples, but at the present time, no method is sensitive enough to measure the Pa-231 and Th-230 daughter isotopes. Candidate methods are accelerator mass spectrometry and resonance ionization mass spectrometry.

Although, as Vitaly also noted, just because the IAEA doesn’t have this capability does not mean that USIC lacks it as well.

What is really required here is a detailed literature survey of mass spectrometry techniques and their accuracies—but that is more like a research project than a blog post. If any reader wants to undertake it, however, you can be assured of somewhere to publish it…

How big are uranium particles?
A second related question is about the typical size distribution of uranium particles on swipe samples. After all, if massive particles are relatively common then the discussion above becomes more-or-less moot. Indeed, Mark Gubrub suggests that the size distribution was typically quite broad. Vitaly also sent me an interesting analysis of the physics of how large particles might form.

…there was a cool paper I saw some time ago, Informativeness of Morphology Analysis of Uranium Microparticles from Industrial Dust at Nuclear Plants by Vladimir Stebelkov (sorry that the English there is a little too Russian, but that adds some flavor for connoisseurs). On the second page Stebelkov mentions in passing that “Uranium molecules and uranium dust particles could form uranium-contained layers during operation of the plant”, and then illustrates it with pictures. Stebelkov was collecting his material from “working areas and ventilation shafts”.

The other article I attach discusses different thing, but also mentions that “The particles formed from uranium hexafluoride are highly hygroscopic and little is known about their long-term stability. Before being collected on swipes they might have been exposed to high temperatures, a high humidity or sunlight. All these environmental factors could have altered their morphology and composition…” and then “In some cases a uniform film of uranium was detected instead of single particles. The fact that the UO₂F₂ particles are highly hygroscopic could explain this phenomenon”.

So I would speculate, without having done a thorough analysis of this, that (a) it may not be so unusual for spherical particles to melt into uniform films on some surface; (b) that process may be facilitated if the surface well contaminated with particles leaves the controlled environment of the plant and gets exposed to moisture, heat, light, etc.

I guess, it would then not take much to shatter such “uranium film” into relatively large splinters, big enough to help the US labs out with age determination.

What was the enrichment level of the uranium particle?
I didn’t discuss this issue much in my original post—but it’s worth mulling on. Dating relies on the presence of U-234, which makes up only 50 ppm of natural uranium. However, being lighter than U-235 it accumulates in the product streams during enrichment. Thus, by the point uranium is 93% enriched in U-235 it is also about 1% enriched in U-234. This was what I used for my calculations.

But, all we actually know is that the particle was HEU; this covers everything from 20% U-235 upwards. The less enriched it was, the less U-234 it contained and the larger it would have to have been for dating purposes. Uranium that is 50% enriched in U-235 contains only 0.43% U-234. A particle of this material would have to be about twice as massive as a particle enriched to 93% to be dated with an equivalent accuracy.

My assumption—that the particle was 93% enriched—is certainly favourable from a USIC perspective (in contrast to my assumption about mass spectrometry accuracy). The dating would be harder to the extent that the particle was less highly enriched.

Moreover, in an operating enrichment plant, particles of all enrichment levels up to the maximum level are present. Therefore, even if the hypothetical North Korean plant was producing weapons-grade HEU (or something close to it) a good slice of luck would have been involved if the one particle that USIC found was sufficiently highly enriched to contain enough U-234 for dating.

Was the particle an outlier?
Yes.

I got this one wrong before. I wrote then that:

Moreover, even if USIC did find one huge particle, basing key policy choices on just one particle is foolhardy. There is an interesting reference in LaMont and Hall to “discarding outliers”. In other words, they occasionally obtained a result that was so wrong (many standard deviations away from the mean) that it was attributed to human error and discarded. If you have just one particle for analysis it is impossible to know whether your one result is one of these outliers.

However, as Josh points out in the comments, the US did have other particles and just one, so far as we know, was dated to 3.5 years. So, it was an outlier. This might be because it was genuinely much younger than the rest, or because of a SNAFU—it is simply impossible to tell. But it does give reason for caution.

Conclusions
There’s something here for everyone. The discussions on mass spectrometry accuracy and the possibility of finding large particles tilt the analysis more in USIC’s direction. The discussion of enrichment levels and outliers do the opposite.

As much as I risk piles by sitting very firmly on the fence let me summarise it this way: USIC’s claim is not impossible, but there are definitely reasons to be cautious. Most crucially, I would urge against making key policy decisions on the basis of one particle.

The view, this morning, of the UN plaza in Vienna (where the IAEA and CTBTO are based) passed onto me by a contact. Thank you, contact.

Happy change day!

As Jeffrey discussed on Saturday, “some” in the US intelligence community (aka DIA) have “increasing concerns that North Korea has an ongoing covert uranium enrichment program”. David Albright, in Glenn Kessler’s story, claims this is based on discovering a single HEU particle that is just 3.5 years old.

Just the day before hearing this news I was, by coincidence, reading this year’s IPFM report. Commenting on Jeffrey’s post, Alex Glaser (one of the Princeton boys who produced the report) summarizes their key conclusion about dating HEU:

As noted in the quote from the IPFM report, it is impossible to determine (or estimate) the age of a micron-sized HEU particle based on the Th-230/U-234 isotope-ratio if the particle is micron-sized, which is what we expect to find on a swipe sample, and less than 20-25 years old. In other words, an HEU sample has to be quite “large” in order to be able to specify an age of less than 5 five years using the Th-230/U-234-method.

The IC’s finding—that the particle in question was just three and half years old—is therefore noteworthy to say the least. So, is it plausible?

The short answer is yes, if the particle was sufficiently large. The larger a particle is, the greater the number of atoms it contains, and hence the smaller the relative error in determining the Th-230/U-234 ratio. So, better questions are: How large would such a particle have to have been? And, how likely is it that USIC would have found a particle of this size?

Those of you without a mathematical/scientific bent may like to skip forward to the results at this point. However, I am going to lay out my analysis in considerable depth so very keen readers can scrutinize it.

Summary of the science
First off, we don’t know what method was used to date the particle. The method I describe here—using thermal ionization mass spectrometry (TIMS)—is probably the best described in the literature (including in an article by LaMont and Hall, two US government scientists at Savannah River) but it is not the only possibility. Apart from other forms of mass spectrometry and other isoptopes of interest, Alex Glaser points out the possibility of using fluorine to date the particle. But here we will stick with TIMS…

All uranium contains a small fraction of U-234, which decays to Th-230, with a half-life of 246,000 years. The age, t, of the sample (more properly, the age since it was last purified) is related to the Th-230/U-234 ratio, R, by the equation:

where β=-6.4 × 10^-6 yr^-1 and K = 0.44 yr^-1 (their relationship to the half lives of U-234 and Th-230 are given here, which also has a nice supplementary discussion of this technique).

Incidentally, a formula that will be useful later is obtained by inverting (1):

Anyway, in terms of experimental technique, the sample must first be chemically treated to separate the U and Th before TIMS can be used to count the number of U-234 and Th-230 atoms. From this R and hence t can be calculated using (1). To correct for inevitable process losses (which may affect U and Th differently), the sample is “spiked” with known amounts of “tracers”. Tracers are isotopes that are not otherwise present in the sample (such as U-233 or Th-229) and they provide a “yardstick” against which to measure the U-234 and Th-230 concentrations.

Error analysis
Because the concentration of U-234 in a sample is much, much higher than the concentration of Th-230, the former can be measured much more accurately than the latter. In fact, given that in very small samples almost all the uncertainty in determining R comes from the uncertainty in the number of Th-230 atoms then

where σ_R is the uncertainty in R and σ_N2 is the uncertainty in the number of Th-230 atoms. N₁ and N₂ denote the number of U-234 and Th-230 atoms respectively.

In the very small samples we are worrying about here, almost all the uncertainty in N₂ comes from so-called counting statistics: the inherent variability in the number of Th-230 particles that hit the detector inside the mass spectrometer (see Table 1 in Lamont and Hall for a detailed “error budget”). Because this process is described by Poisson statistics then, if there were no process losses, we would expect σ_N2=N₂^0.5. In reality, because only a fraction of the Th-230 atoms in the sample contribute to the mass spectrometry then the uncertainty in N₂ is given by

where A is a constant (much bigger than 1) that undoubtedly depends on the specific experimental set-up. Physically A^-2 represents the fraction of Th-230 atoms that contribute to the spectrometry.

Finally, by differentiating (1), associating dt and dR with σ_t and σ_R, and using (2), (3) and (4), I finally obtain:

where σ_t is the uncertainty in the age of the particle.

Note that all the constants in (5) are known, except for A. Fortunately, the paper by LaMont and Hall provides enough information to estimate A=6200 for their experimental set-up. I won’t go through the details of that calculation here (but can supply them on request, of course).

I want to point out at this stage that, applied to older particles, my model leads to significantly different conclusions from the 2008 IPFM report. As stated above, that report concludes that you need a particle of about 3 microns in diameter to date it if it is a few decades old. In contrast, my model predicts, for instance, that a particle of 50 microns in diameter would be needed to date a 25 year old particle to within an accuracy 5 years. I believe the difference emerges because the IPFM conclusion is based on the particle size needed to contain a detectable quantity of Th-230. However, I think that a larger amount of Th-230 is needed to be able to measure the number of atoms sufficiently accurately for dating. However, as I say at the end of this posting, I am by no means completely confident in my model and given the quality of IPFM’s work the fact that my conclusion differs from theirs does worry me. Anyway, onto the results using my model…

Results
If you skipped the last couple of sections: welcome back.

The graph below shows the diameter of a particle (in microns) against the uncertainty in its age (in years), assuming a spherical particle with a nominal age of 3.5 years and a density of 10 g cm^-3. Apologies for the lack of axis labels—I am having Excel problems…

Plot of particle diameter (x-axis, x10^-6m) against uncertainty in age (y-axis, years)

Now, USIC told Albright that the age of the particle they found was 3.5 years. Given they cite the age to the nearest half year I take their uncertainty to be somewhere between six months and a year. Based of the graph above, this leads to a particle diameter of between 80 and 120 microns or, in terms of mass, between 2 and 7 microgrammes.

This would represent a very large particle. In fact, it is two orders of magnitude larger than the size normally found on a swipe sample: 1-3 microns (according to IPFM). I simply don’t know enough about environmental sampling to know whether such uber particles do occur from time to time. If any of you do, please feel free to comment.

It’s hard to say therefore whether USIC’s detection of a 3.5 year old particle is plausible. Nonethless, I would certainly urge caution in interpreting this claim. Assuming my analysis is correct (and that is a big assumption—see below), USIC has either found a truly huge particle (which may be unlikely) or they have a worryingly large error bar on their result (potentially a few years or more).

Moreover, even if USIC did find one huge particle, basing key policy choices on just one particle is foolhardy. There is an interesting reference in LaMont and Hall to “discarding outliers”. In other words, they occasionally obtained a result that was so wrong (many standard deviations away from the mean) that it was attributed to human error and discarded. If you have just one particle for analysis it is impossible to know whether your one result is one of these outliers.

Should you believe me?
Good question. Let me be very clear about the limitations of this analysis.

The above analysis has not been peer reviewed. In particular, I had to postulate equation (4) because I couldn’t find a relevant discussion of this issue in the literature. Moreover, my estimate of mass spectrometry accuracy (essentially represented by the constant A) is based on one paper that is four years old. If TIMS has moved on since then, or if USIC employed some other, more accurate technique, then it may have been able to get away with a much smaller particle. All of this I freely acknowledge. I don’t claim this is anything more than a first, rough attempt to get something out quickly to help inform the debate about North Korean enrichment. Please don’t treat this as anything more.

Friend of Wonk, Mark Fitzpatrick, pointed me in the direction of an interview on Egyptian TV with, Yousry Abushady, a section head in the IAEA Department of Safeguards, about the alleged Syrian reactor.

Part 2 can be found here.

Speaking in his “personal capacity”, Abushady disputes that the BoE was a Magnox reactor. In part two, he claims 30-40 errors in the CIA briefing to Congress (If you don’t recall the little movie, here is the video and the text of the press briefing).

Alshady elaborates on only one alleged “error,” however. During the first segment, he claimes that 5MWe reactor at Yongbyon is 50m high and that the BoE is only 10m high. Even assuming that some of the BoE is underground, he says this disparity is too much for the reactors to be of the same type.

So, is this a startling revelation undermining US claims or an IAEA inspector with an anti-US bias going off on one, or even just an honest guy making a mistake?

I am off Italy this afternoon (along with Jeffrey as it happens) so don’t have time to get into this in as much depth as it merits but, off the top, here are my thoughts …

There are two key questions:

1. Is Abushady right about the height of the North Korea reactor?

I cannot find a good independent number for the height of the North Korean reactor. I’m sure it’s out there somewhere so please do comment if you know it.

However, let’s assume that 50m is right. What’s not clear to me is whether Abushady is including the primary stack (if that’s the right term) of the North Korean reactor in this number (and from his picture it looks like he might be). If he is, his comparison is rather disingenuous since the Syrian reactor doesn’t have an equivalent structure so the relevant height for comparison purposes should be the height of roof on the building—considerably less than 50m.

2. Is Abushady right about the height of the Syrian reactor?

Well, the first place to look for a discussion of this question is, of course, the comments in this blog!

I don’t have time to revise in detail that outstanding discussion now but a consensus seemed to be emerging in the 15—20m range, i.e. somewhat higher than Abushady says. And remember, you have to add to this however much of the reactor is supposed to be underground.

In summary, my initial, not-too-fully considered reaction is to be skeptical of Abushady. My guess is that he is overestimating the height of Yongbyon (by including the stack) and underestimating the height of the BoE. But, Abushady is, as he says, a guy that knows a lot about the North Korean reactor so I don’t want to sound too dogmatic.

What I would say, however, is that it is unhelpful to have such analysis coming from an IAEA official in his “personal capacity”. If the IAEA has concerns about this they should be in the official reports not spread in this way.

Finally, if any of you speak Arabic (as I’m sure a number of you do) I would love a sense of how accurate the translation is.

New Year’s resolution: Get back to blogging regularly.

There were a couple of stories that I blogged about towards the end of last year—potential nuclear sales to Pakistan and Israel—that I had been meaning to follow up on but never got around to in the debris that was the end of 2008. For some of you, particularly readers of Mark Hibbs, some of this might be old news. If that applies you, my apologies.

According to a story from Hibbs in Nucleonics Week from November 6, it turns out that the Pakistan-China deal never actually was.

Apparently not only is there no agreement for new reactor sales but, at the moment, Pakistan could not afford them anyway. So, where did the story come from? According to Hibbs, it originated in Pakistan:

Some of these officials [his sources for the story] suggested that Pakistan last month raised the issue of Chinese PWR imports to media outlets to put pressure on the NSG to grant Pakistan—as it did India in September—an exemption from NSG trade restrictions banning reactor exports to states without full-scope safeguards.

In the December 15 Nucleonics Week Hibbs has an excellent background piece on a potential US-Israel deal in return for Israeli ratification of the CTBT. Predictably, many NSG members are unenthusiastic:

One official said that, in 2007 and 2008, some NSG members notified the US informally that they would not support granting an exception to Israel, and officials from some NSG member states suggested this month that CTBT ratification by Israel would not suffice to prompt the NSG to permit vendors in NSG members to export controlled nuclear items to Israel.

Several NSG representatives said that, to qualify for an exemption, Israel would have to take steps consistent with a future global fissile material cut-off treaty, or FMCT, such as agreeing to a verified shutdown of its reactor at Dimona, at the Negev Nuclear Research Center, which is widely believed to have produced plutonium for nuclear weapons.

Much also depends on personnel changes within Israel. Within the Israeli Atomic Energy Commission, the Director General Gideon Frank and his deputy Ariel Levite have retired and were replaced by Shaul Chorev and David Danielli respectively. How they view the trade-offs potentially necessary to effect the deal is unclear. There will also certainly be a change at the very top with elections and Olmert standing down. In particular, Netanyahu who may well win, is known to vehemently oppose an FMCT.

The prospects for either of these deals in the short term are clearly poor (and so much the better some of us would say). In the longer term, however, I wouldn’t write them off. One interesting tidbit I picked up over Christmas is that the current IAEA Director-General is very strongly in favour of both of them. Although, of course, he isn’t much longer for this job. We wait to hear what his successor thinks.