The U.S. Air Force’s 701 Munitions Support Squadron at Kleine Brogel Air Base must protect and handle the nuclear weapons at the base.

An astounding statement by a Belgian defense official has pointed an unexpected light on the apparent location of nuclear weapons at the Kleine Brogel Air Base in Belgium.

After a group of peace activists climbed the base fence and made their way deep into an area assumed to store nuclear weapons, Ingrid Baeck, a chief spokesperson for the Belgian Ministry of Defense, bluntly told Stars and Stripes: “I can assure you these people never, ever got anywhere near a sensitive area. They are talking nonsense….It was an empty bunker, a shelter,” she said and added: “When you get close to sensitive areas, then it’s another cup of tea.”

Baeck did not go so far as to explicitly confirm or deny if there were nuclear weapons on the base, but the Belgium Ministry of Defense’s mission statement for the 10^th Tactical Wing clearly shows that it has a nuclear mission (see Figure 1).

Figure 1: Belgian 10th Tactical Wing Mission

The Belgian Ministry of Defense’s mission statement for the 10th Tactical Wing (10 W Tac) at Kleine Brogel clearly lists a nuclear mission. Emphasis added.

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Shelter Searching

It is unclear whether Baeck as a spokesperson actually knows where the weapons are stored or if “sensitive area” only refers to the particular shelter the activists reached. But her statement that the activists “ever got anywhere near a sensitive area” inadvertently redirects the attention to the western area of the base.

Kleine Brogel has 26 Protective Aircraft Shelters (PAS) located in three clusters: Area 1 at the western part of the base with 11 shelters; Area 2 at the center of the base also with 11 shelters; and Area 3 at the eastern end of the base with four shelters (see Figure 2).

Figure 2: Nuclear Weapons Storage Areas

Estimated locations for nuclear weapons at Kleine Brogel Air Base have changed over the years. Click image for large version.

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During the Cold War, nuclear weapons were stored in the Weapons Storage Area northeast of the base, while aircraft loaded with nuclear weapons stood alert in the shelters in Area 3.

Area 2 has long been the suspected nuclear weapons storage area, given its 11 shelters, pronounced fencing, and separation from the outer base perimeter. This is the area the activists managed to penetrate on January 31^st.

Baeck’s statement appears to draw the attention to Area 1 at the western end of the base where 11 shelters are clustered. It also has an additional fence perimeter that appears to have been improved since 2006, but the gates were open on a satellite image dated April 8, 2007. Moreover, the area is close to the outer base fence, with the busy N748 highway only 225 feet (68 meters) from one shelter and another shelter only 134 feet (40 meters) from a residential neighborhood. Jeffrey L also has an interesting photo interpretation.

Whether the nuclear shelters necessarily have to be in one cluster inside the same perimeter is unknown, although safety and management issues seem to suggest so.

The Weapons Security and Storage System (WS3)

Only 11 of the 26 Protective Aircraft Shelters at Kleine Brogel are equipped with the Weapons Storage Security System (WS3), a nuclear weapons storage system unique to Europe. The system at Kleine Brogel was completed in 1992.

The mechanical part of the WS3 includes a Weapons Storage Vault (WSV), a reinforced concrete foundation and a steel structure recessed into the floor of the shelter. The vault platform can be elevated out of the concrete foundation by means of an elevator drive system to provide access to the weapons in two stages or levels, or can be lowered into the floor to provide protection and security for the weapons. The floor slab is approximately 16 inches (40 cm) thick. Sensors to detect intrusion attempts are embedded in the concrete vault body.

Each of the 11 vaults can store up to four B61 bombs, but normally contains only one or two for a total of 10-20 bombs currently at Kleine Brogel.

Location of the vault inside the shelter depends on the size of the shelter and the proximity of conventional weapons storage racks. Two layouts are in use (see Figure 3), and the vaults at Kleine Brogel are the smaller located at the front-left end of the shelter.

Figure 3: Weapons Storage Vaul Locations

The location of the underground Weapons Storage Vault depends on the size of the aircraft shelter. Kleine Brogel shelters use the right-hand layout.

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The vaults are rarely visible on photos from outside the shelters, but in this unique photo (see Figure 4) taken at nearby Volkel Air Base in the Netherlands in 2009 the outline of the vault can be seen in the front-left corner (right in the picture) of the shelter.

Figure 4: External View of Munitions Storage Vault

A vault cover is visible inside this shelter at Volkel Air Base in the Netherlands. The picture of the specially painted F-16 (no. J-015) was taken during a pilot ceremony in 2009. Reprinted with permission. Original photo at Touchdown Aviation.

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The vault can be elevated in two stages, halfway to provide access to the top rack, or fully to provide access to the lower rack as well. An example of halfway elevation is the photo below showing the command of U.S. Air Forces in Europe, General Roger Brady, receiving a briefing next to a vault at Volkel Air Base in June 2008 (see Figure 5) (he also visited Kleine Brogel). The visits happened shortly after the Blue Ribbon Review report concluded that “most sites” storing nuclear weapons in Europe did not meet DOD security standards.

Figure 5: Halfway Elevation of Weapons Storage Vault

This picture, taken inside a shelter at Volkel Air Base, shows Gen. Grady receiving a briefing from a member of the 703rd MUNSS. The vault is halfway raised showing one B61 bomb, with the lower bomb rack hidden below the floor level.

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If fully elevated the vault appears as on the image below (see Figure 6). The base name is unknown, but given the location of the vault it appears to be inside a large shelter at a U.S. base, possibly Aviano Air Base in Italy or Ramstein Air Base in Germany (all B61s were removed from Ramstein in 2005).

Figure 6: Full Elevation of Weapons Storage Vault

Full elevation of the Weapons Storage Vault inside what appears to be an aircraft shelter at Aviano Air Base or Ramstein Air Base.

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What is Security?

Kleine Brogel base commander Col. Fred Vansina insisted that the penetration of the base by the activists did not constitute a security incident: “Our installations are very well secured, in different ways,” there was “no single security incident, whatever the activists claim.”

A nuclear base is a sensitive area and unauthorized personnel meandering around deep inside its inner perimeters is a security incident, but Vansina’s definition appears to require an unauthorized and dangerous approach of a nuclear facility. Both he and Baeck have great confidence in the WS3 and the security forces’ ability to protect the weapons under all circumstances.

I agree that it would be very difficult for anyone to steal or destroy the weapons under normal circumstances when they’re stored underground. But it is the abnormal circumstances that concern me; weapons are occasionally brought up from the vault, serviced, and moved (see Figure 7). Overconfidence is dangerous because incidents and accidents have a nasty habit of happening in ways that were not anticipated. And that requires us to weigh the risks against the necessity of the deployment, a necessity I have an increasingly hard time to see.

Figure 7: Halfway Elevation of Weapons Storage Vault

The safety of the underground Weapons Storage Vault no longer applies when nuclear bombs in Europe are brought up for maintenance or transport. A 1997 Air Force study even found a risk of lightning causing a nuclear detonation.

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Status of Nuclear Weapons in Europe

The 10-20 weapons at Kleine Brogel are part of a stockpile of an estimated 150-200 U.S. nuclear bombs scattered in 87 vaults at six bases in five countries, a reduction from approximately 480 bombs in 2001. My current estimate looks like this (see Figure 8):

Figure 8:

Click image to download larger pdf-version.

This publication was made possible by a grant from Carnegie Corporation of New York and Ploughshares Fund. The statements made and views expressed are solely the responsibility of the author.

Peace activists walked one kilometer onto a US nuclear weapons storage site in Belgium for more than one hour before security personnel reacted. Click image for larger version. (For an update to this map, go here)

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By Hans M. Kristensen

A group of people last week managed to penetrate deep onto Kleine Brogel Air Base in Belgium where the U.S. Air Force currently deploys 10-20 nuclear bombs. (For an update to this blog, go here)

Fortunately, the people were not terrorists but peace activists from a group known as Vredesactie, who managed to climb the outer base fence, walk cross the runway, breach a double-fenced security perimeter, and walk into the very center of the air base alongside the aircraft shelters where the nuclear bombs are thought to be stored in underground vaults.

A Nuclear Cake Walk

The activists climbed the outer base fence (1), breached the inner double-fence (2), tagged a nuclear aircraft shelter (3), walked across the tarmac (4), before being arrested (5) after more than one hour inside the base. The numbers on the images correspond to the location of the numbers on the map above.

The activists penetrated nearly one kilometer onto the base over more than an hour before a single armed security guard appeared and asked what they were doing. Soon more arrived to arrest the activists, who later described: “The military blindfolded for hours, they forced us to kneel in the snow, arms outstretched at 90° and threatened us if we intend to return to the base in the months to come.”

The activists videotaped their entire walk across the base. The security personnel confiscated cameras, but the activists removed the memory card first and smuggled it out of the base. Ahem…

In June 2008, I disclosed how an internal Air Force investigation had concluded that most nuclear weapons sites in Europe did not meet US security requirements. The Dutch government denied there was a problem, and an investigative team later sent by the US congress concluded that the security was fine.

They might have to go back and check again.

The nuclear bombs at Kleine Brogel are part of a stockpile of about 200 nuclear weapons left in Europe after the Cold War ended. Whereas nuclear weapons have otherwise been withdrawn to the United States and consolidated, the bombs in Europe are scattered across 62 aircraft shelters at six bases in five European countries. The 130-person US 701^st Munitions Support Squadron (MUNSS) is based at Kleine Brogel to protect and service the nuclear bombs and facilities.

They might have to go back to training.

The activists will likely be charged with trespassing a military base but they should actually get a medal for having exposed security problems at Kleine Brogel. And this follows two years of the Air Force creating new nuclear command structures and beefing up inspections and training to improve nuclear proficiency following the embarrassing incident at Minot Air Force Base in 2007. Despite that, the activists not only made their way deep into the nuclear base but also discovered that the double-fence around the nuclear storage area had a hole in it! “We’re not the first,” one of the activists said.

NATO needs to get over its obsession with nuclear weapons and move out of the Cold War and the Obama administration’s upcoming Nuclear Posture Review needs to bring those weapons home before the wrong people try to do what the peace activists did.

This publication was made possible by a grant from Carnegie Corporation of New York and Ploughshares Fund. The statements made and views expressed are solely the responsibility of the author.

On 13 January, Ivanka Barzashka and I gave a briefing at the AAAS on our work regarding Iran’s uranium enrichment capacity.  Joshua Pollack also gave a briefing, which he has described.  Joshua’s analysis is thorough and interesting but I think I would use a different distinction than the “actual” and “nominal” values that he defines.

Pollack shows how the estimates of the capability of Iran’s centrifuge, the IR-1, have declined over time.  That is intriguing but I worry that it makes the calculations that Ivanka and I and others have performed using data reported from International Atomic Energy Agency (IAEA) on-site inspections seem like the next step in a series of similar estimates.  They are not.  There are two very different types of approaches being taken here.  Here I present an analogy that I think might make the differences clear. (more…)

Katsuya Okada and Hillary Clinton met in September 2009.

By Hans M. Kristensen

The Japanese government has officially rejected claims made by some that Japan is opposed to the United States retiring the nuclear Tomahawk Land-Attack Missile (TLAM/N).

The final report of the Congressional Commission on the Strategic Posture of the United States from May 2009 emphasized the importance of maintaining the TLAM/N for extended deterrence in Asia by referring to private conversations with specifically “one particularly important ally” (read: Japan) that “would be very concerned by TLAM/N retirement.”

In a letter sent to Secretary of State Hillary Clinton on December 24, 2009, Japanese Foreign Minister Katsuya Okada explicitly says that the Japanese government has expressed no such views.

The Japanese Foreign Minister’s letter explicitly refers to the Commission: “It was reported in some sections of the Japanese media that, during the production of the report of the Congressional Commission on the Strategic Posture of the United States released in May this year, Japanese officials of the responsible diplomatic section lobbied your government not to reduce the number of its nuclear weapons, or, more specifically, opposed the retirement of the United States Tomahawk Land Attack Missile – Nuclear (TLAM/N) and requested that the United States maintain a Robust Nuclear Earth Penetrator (RNEP).

I don’t know who made a reference to RNEP (the Commission didn’t; perhaps it was a reference to earth-penetration capabilities in general rather than RNEP per ce), but Okada’s rejection of the TLAM/N claim is clear:

“[A]lthough the discussions were held under the previous Cabinet, it is my understanding that, in the course of exchanges between our countries, including the deliberations of the above mentioned Commission, the Japanese Government has expressed no view concerning whether or not your government should possess particular [weapons] systems such as TLAM/N and RNEP.” (my emphasis)

Okada’s statement suggests that he has checked the government’s files. It also matches the statement made by Admiral Timothy J. Keating, the former Commander of U.S. Pacific Command, in July 2009, that he was “unaware of specific Japanese interests in the” TLAM/N.

If the TLAM/N were retired, Okada says, Japan would of course like to be informed about how this would affect extended deterrence and how it could be supplemented. I hope “supplemented” means by other existing nuclear and non-nuclear means, not by new nuclear weapon system.

It seem so, because Okada writes that he favors nuclear disarmament, and he also expresses interest in the proposal made recently by the International Commission on Nuclear Non-Proliferation and Nuclear Disarmament (ICNND) – and many others – that the role of nuclear weapons be restricted to deterrence of the use of nuclear weapons. That is important for the Japanese government to say because one of the current missions for U.S. nuclear weapons involve North Korean chemical and biological attacks on Japan. Apparently, closer consultations between the United States and Japan on extended deterrence issues would be a good idea.

It seems more and more that the TLAM/N claim resulted from a shady collusion between a few U.S. and Japanese officials (some current and some former) who sought to present private views as more than that in an effort to put brakes on the Obama administration’s disarmament agenda.

Hopefully the pending Nuclear Posture Review will not be led astray.

This publication was made possible by a grant from Carnegie Corporation of New York and Ploughshares Fund. The statements made and views expressed are solely the responsibility of the author.

Russia’s Teykovo 4 missile garrison northeast of Moscow is undergoing major upgrades for new SS-27 mobile nuclear missiles. Click image for large illustration of the changes.

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By Hans M. Kristensen

The latest overview of Russia’s nuclear forces produced by Robert Norris from NRDC and myself is now available on the website of the Bulletin of the Atomic Scientists.

We estimate that Russia currently (January 2010) deploys approximately 4,600 nuclear weapons, down from roughly 4,800 a year ago. The arsenal includes some 2,600 strategic warheads and about 2,000 warheads for nonstrategic forces. Another 7,300 weapons are thought to be in reserve or awaiting dismantlement for a total inventory of approximately 12,000 nuclear warheads. We estimate the weapons are stored at 48 permanent storage sites.

SS-27 Modernization at Teykovo

One of the interesting developments is Teykovo northeast of Moscow where four missile garrisons are in the process of upgrading from the SS-25 road-mobile intercontinental ballistic missile (ICBM) to the newer SS-27. One base still has SS-25s while the other three are in various stages of upgrading.

The SS-27 comes in two versions: single-warhead SS-27 Mod 1 (Topol-M) and the multiple-warhead SS-27 Mod 2 (RS-24). The two versions can be deployed in silos or on mobile launchers. All Teykovo missiles are mobile. Fifteen SS-27 Mod 1s have already been deployed, and the Russian military stated repeatedly in 2009 that the first SS-27 Mod 2 (RS-24) would become operational at Teykovo by the end of the year, which we wrote in our overview. That apparently did not happen after all and the system is now expected to become operational sometime in early-2010.

Commercial satellite images taken over the past five years clearly show major construction work at the garrisons. The newest images from late-2009 show that two garrisons appear to be active, one is undergoing major upgrades (see image above), and one was inactive as of September 2009.

Teykovo ICBM Garrison Status 2009

Click table for larger version.

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Teykovo 1 (56°48’33.11″N, 40°10’15.89″E) appears to be active with the SS-25. Nine launchers (one regiment) are deployed. A satellite photo from September 17, 2009, shows no construction. The base might be converted to SS-27 in the future.

Teykovo 2 (56°55’0.42″N, 40°18’31.39″E) no longer has operational SS-25s with all missile garages missing in a satellite image from September 17, 2009. No construction has begun but the base might be converted to SS-27 in the future.

Teykovo 3 (56°55’56.98″N, 40°32’38.47″E) appears to have almost completed its upgrade. Major construction occurred in 2006-2008 and some remaining construction is visible in a satellite image from September 6, 2009. Nine SS-27s are operational.

Teykovo 4 (56°42’15.10″N, 40°26’25.29″E) appears to be in the process of upgrading to SS-27, with six of eventually nine launchers apparently operational. Deployment of the first three SS-27 Mod 2 (RS-24) was scheduled for late-2009 but appears to have been delayed to later this year.

Modernization and Fear Mongering

Russian nuclear modernization is a hot topic in Washington with some trying to block new nuclear arms reductions by claiming that the United States is falling behind. That is fortunately far from the truth (see here and here) and the upgrade at Teykovo has been long in the coming and slow.

Like the United States, Russia is reducing its nuclear weapons but also modernizing its remaining forces. How the Kremlin plans to reconcile this modernization with the pledge to pursue nuclear disarmament that president Dmitry Medvedev made with his U.S. counterpart in 2009 will be interesting to see in the years ahead.

This publication was made possible by a grant from Carnegie Corporation of New York and Ploughshares Fund. The statements made and views expressed are solely the responsibility of the author.

The government’s much anticipated Nuclear Posture Review, originally scheduled for release in the late fall, then last month, then early February is now due out the first of March.  The report is, no doubt, coalescing into final form and a few recent newspaper articles, in particular articles in Boston Globe and Los Angeles Times, have hinted at what it will contain.

Before discussing the possible content of the review, does yet another release date delay mean anything?  I take the delay of the release as the only good sign that I have seen coming out of the process.  Reading the news, going to meetings where government officials involved in the process give periodic updates, and knowing something of the main players who are actually writing the review, what jumps out most vividly to me is that no one seems to share President Obama’s vision.  And I mean the word vision to have all the implied definition it can carry.  The people in charge may say some of the right words, but I have not yet discerned any sense of the emotional investment that should be part of a vision for transforming the world’s nuclear security environment, of how to make the world different, of how to escape old thinking.  As I understand the president, his vision is truly transformative.  That is why he was awarded the Nobel Peace Prize.  His appointees who are developing the Nuclear Posture Review, at least the ones I know anything about, are incredibly smart and knowledgeable, but they are also careful, cautious, and, I suspect, incrementalists who might understand intellectually what the president is saying but don’t feel it (and, in many cases, fundamentally don’t really agree with it).  A transformative vision not driven by passion will die.  As far as I can see (and, I admit, I am not the least bit connected so perhaps I simply cannot see very far) the only person in the administration working on the review who really feels the president’s vision is the president.  Much of what I hear from appointees in the administration has, to me at least, the feel of “what the president really means is…”   If the cause of the delay is that yet more time is needed to find compromise among centers of power, reform is in trouble because we will see a nuclear posture statement that is what it is today neatened up around the edges.  But if the delay is because the president is not getting the visionary document he demands, delay might be the only hopeful sign we are getting.

Now, onto the possible content of the review:  The main question to be addressed by the review is what the nuclear doctrine and policy of the United States ought to be.  This has sparked a secondary debate about just how specific any declaration of policy should be and the value of declaratory policy at all.

Some hints coming out of the administration suggest that the new review may explicitly state that the sole purpose of nuclear weapons be specifically limited to countering enemy nuclear weapons, what we and others have called a “minimal deterrence” doctrine.  Currently, the United States claims that chemical and biological weapons may merit nuclear attack and that could go away with the current review.

Most reports leaking out from the review participants hint that the NPR almost certainly will not include a declaration that the United States will not be the first to use nuclear weapons.  The current U.S. policy is to intentionally maintain ambiguity about how and when we might use nuclear weapons, to keep the bad guys guessing.  The new review could keep that basic idea and still be a little less ambiguous around the edges.

Some question the value of having a declaratory policy at all.  For example, if a no-first-use policy can be reversed by a phone call from the president, what does it actually mean?   As Jeffrey Lewis argues, if having a declared policy causes an intense drilling down into what-ifs, it can increase suspicion and do actual harm.  (Although the example Lewis offers raises questions about whether China should have a no-first-use policy and is not particularly relevant to whether the U.S. should.)

A bigger problem with any declaratory policy is figuring out what it actually means.  Do we agree on what “no first use” means?  I think it means that we will not be the first to explode a nuclear weapon.  But, for example, in a recent article in Foreign Affairs, Lieber and Press argue that the United States could be justified in using nuclear weapons if an adversary first “introduced” nuclear weapons into a conflict, where “introduce” might be to explode one, but might also include putting them on higher alert, moving them, or simply implying their relevance to the contest.  So a nuclear war-planner and I could agree on a no-first-use policy and have differing, almost opposite, views of what that meant.

But if statements of doctrine don’t mean anything, then why the big deal?  Why would the nuclear establishment invest any political capital fighting for or against them?  While it is true that doctrinal statements are always taken with a huge grain of salt by other nations (just as the United States applies a steep discount to statements coming from others), they do make a difference in the domestic debate.  In the previous administration, the Department of Energy went to the Congress with a request to build a new facility to build the plutonium cores or “pits” for 250 new nuclear warheads every year.  This made no sense whatsoever;  it was completely out of synch with our own plans for future nuclear forces and Congress voted it down because the DOE was not remotely able to justify its request.  The DOE proposal went down to 125, then 80, and some current variations on the basic proposal are for a dozen or so, which actually makes some sense.

So doctrine and declaratory policy are important in very concrete ways when they can affect force structure decisions, including the numbers and types of weapons we have, their capabilities, and how they are deployed.  Moreover, these are the sorts of changes that other nations will see and pay attention to.

The uncertainty of the link between words and weapons is what causes wariness on every side of the debate.   Foreign governments might not believe our declarations but such declarations might form the basis for changes in the U.S. nuclear force structure, with all the implications for budgets and personnel, weapons, bases, and jobs back home.  That is why the nuclear establishment is resisting.  On the other hand, those who desire fundamental and profound change could be completely hoodwinked by nice sounding words that allow the status quo to coast ahead on its own momentum.

The danger I see is that, if discussion is so tightly focused on what we say, then too little attention will be given to what we do.  If we take our declarations seriously, they should have profound effects on the nuclear posture but I can imagine big changes in the review with little real physical change actually resulting.  For example, if we take seriously a no-first-use policy, our deployment of forces could be radically different.  Reentry vehicles could be stored separated from their missiles, missiles in silos could be made visibly unable to launch quickly, for example, by piling boulders over the silo doors.  Much of the ambiguity in any verbal statement of doctrine is squeezed out when we discuss the concrete questions of what the forces look like.  The nuclear war-planner and I might have effectively opposite definitions of “no first use” but we would agree entirely on what it means to piles boulders on our ICBM silo doors.

What I would hope to see come out of the NPR is not simply a statement of no first use but a plan for, for example, taking our nuclear weapons off alert.  We will certainly hear that nuclear weapons are for deterrence, perhaps that they are only for deterrence.  But that has become utterly meaningless because the definition of deterrence has been warped to the point that it can now be defined as whatever it is that nuclear weapons do.  Indeed, nuclear weapons are often simply called our “deterrent.”  Michele Flournoy, the current Undersecretary of Defense in charge of the NPR process, wrote a report while at CSIS describing how U.S. nuclear weapons should be able, among other things, to execute a disarming first strike against central Soviet nuclear forces, the better to “deter.”  When a word has that much flexibility, I don’t care whether it gets included in the posture statement or not but I do care whether we mount our nuclear weapons on fast flying ballistic missiles or on slow, air-breathing cruise missiles.

If we take seriously some of the statements that might come out of the review, then we can start to imagine radically different force structures.  For example, if the requirement for nuclear preemption is removed and the number of nuclear targets is substantially reduced, then new ways to base nuclear weapons become feasible.  We could, for example, store missiles in tunnels dug deep inside a mountain where the missiles would be both invulnerable and impossible to launch quickly.  We could invite a Russian to live in a Winebago on top of the mountain to confirm to his own nuclear commanders that we were not preparing our missiles for launch.

These are things the world can see.  Indeed, if we have no interest in a first strike capability, we have every incentive to invite the world to come in and see for themselves.  These are the types of changes that need to occur in the U.S. nuclear force structure and, if they do, debate about the words in the review is less important.

Happy New Year.  We at FAS are a serious, hard-working lot but I thought I would start the year with a blog somewhat less Earth-shattering than we normally do.  The following is the result of some research made possible by free time over the holidays.

It is with a combination of despair and delight that we discover that what we thought to be true is not. I guess it is all part of learning.  Thus with mousetraps and ping-pong balls.

I often get science questions from film-makers.  Most recently from a production group doing a piece on nuclear energy and nuclear weapons.  I was explaining chain reactions and mentioned the famous demonstration using mousetraps and ping-pong balls.  If you are a techie sort reading this blog, you have probably seen one demonstration or another;  from my childhood, I can remember one featured in Disney’s 1957 Our Friend the Atom.  (The cloud chamber demo is also very cool, and check out the extremely trendy lab coat the female lab tech is wearing;  the 50’s were, indeed, the good old days).

After this discussion with the film team, I got online and started looking for other examples of the demonstration.  I expected to find some but not many.  I was particularly curious to find how large was the biggest layout that had ever been done.  Doing this demonstration is a lot of work after all, setting all those mousetraps and carefully placing the ping-pong balls on top.  And one mistake and…start all over.  (And what do you do afterwards with hundreds of mousetraps and ping-pong balls?)

In my search, I discovered a few very slow motion videos that show that the demonstration is entirely misleading.  The mousetraps-with-ping-pong-balls is a terrible analog for a nuclear chain reaction.

The basic idea is simple:  In a nuclear fission chain reaction, one neutron splits an atomic nucleus, or induces the fission of the nucleus.  (I think the latter, while fancy, is actually a better term.  “Splitting” the nucleus suggests to me shooting a bowling ball with a rifle bullet and breaking it in two.  That isn’t really what happens.  The neutron may be fast or it may be very slowly passing by when it falls into the nucleus and finds an unmated neutron.  The binding energy of those neutrons releases so much energy into the nucleus that it comes apart.  The kinetic energy of the neutron can be negligible compared to the binding energy released.  That is why slow moving neutrons are more likely than fast neutrons to cause the fission of a susceptible nucleus:  the kinetic energy of the neutron is unneeded and the slower neutrons are easier to catch.)  The nucleus splits into two big chunks, which will become the nuclei of new, lighter atoms, but in the process it releases a couple of neutrons.  These neutrons go on to cause additional fissions, which produces more neutrons, which produce more fissions, and so on.  If the reaction is allowed to go as fast as possible, the number of neutrons and the rate of fission increase exponentially and very rapidly and an explosion results.  In a nuclear reactor, the rate of reaction is carefully controlled to keep a steady rate of fission.

So the macroscopic model is the array of mousetraps with each trap topped by a pair of ping-pong balls.  One ball is dropped onto the array and trips a trap.  It is the energy of the trap, not the energy of the ball that flings the other two balls up in the air.  These come down, setting off two more traps, releasing four balls.  These four balls set off four traps releasing eight balls, and so forth and, in a few seconds, ping-pong balls are flying everywhere and all the traps have been tripped.

Or so we were lead to believe.  (We can’t even believe Walt Disney?)  But some of the videos are slow motion and bear careful study.  This one in particular (be sure to have your sound turned on) shows that most of the traps are tripped, not by balls, but by flying traps.  Note that balls often hit traps and knock the balls free without tripping the traps.  This is the equivalent of the (n,3n) nuclear reaction, which would be very rare because it requires breaking apart a pair of fermions, and fermions just love their pairs.  A much more common nuclear reaction is (n,2n), which is equivalent to having one ball come in and knock just one ball off.  With nuclei, this is not common enough to sustain a chain reaction.

I have not done a careful counting but my uncareful counting shows that most of the ball impacts occur without setting traps off.  That is OK, it is the equivalent of a collision in which no reaction takes place, which is, at least for some energies, the most likely thing to happen when a neutron hits a nucleus.  In the video above, keep your eye on one trap about a third of the way up from the bottom and a quarter of the way in from the right hand side.  It is hit by several balls during the whole chain reaction and at the end remains unsprung.

Of course, eventually a ball will set off a trap but then something interesting happens:  the trap goes flying.  (If we really wanted to demonstrate fission, the trap would have to split in two, but we will overlook that.)  And it is the big, heavy trap that sets off neighboring traps when it hits the ground.  The analog would be that the fission products, not the neutrons, induce further fissions, say, a big heavy cesium nucleus runs into the nearby uranium nucleus and caused it to split.  Of course, that never happens.

Another interesting case is here;  at time 2:05, note right along the center, a column of traps snaps in sequence when clearly the balls go flying straight up and do not have time to set off the next trap.  What is happening is that the hammer (that is the bar that actually whacks the mouse on the back of his neck;   I had to look it up) swings from one side to the other and, through conservation of momentum, the base of the traps scoots along in the opposite direction.  The trap then whacks the next trap in line, setting it off, and that hits the next, and so on.  The video shows clearly that the ping-pong balls have nothing to do with the process in that particular case.  (Before you get all huffy about conservation of momentum, remember that, because these demonstrations are taking place in a gravitational field with the traps sitting on the floor, there is an asymmetry, for example, when the hammer is going up, it pushes the trap against the floor and doesn’t move it but when the hammer is on the way down, it can lift the trap up and scoot it in the opposite direction.)

Obviously, some balls do trip some traps; I am just saying that that is not the dominant process, it is traps tripping traps. To see a nice example of traps tripping traps, watch the first video above, right in the center, at 3:08, and see one trap land on another, be actually trapped by it, and then the two go off in a nice 2001: A Space Odyssey-style weightless waltz.  I guess this is the equivalent of a fusion that might be seen in a heavy ion accelerator.

So, what would be a good analog?  If you meet the following criteria:

(1)  You want to demonstrate several aspects of neutron-induced nuclear fission chain reactions,

(2)  You have several hundred mousetraps and twice as many ping-pong balls handy, and

(3) You have WAY too much time on your hands,

then you may want to construct the following demonstrations.  I know I am not going to be doing this.  (And don’t forget to video tape everything and post it on YouTube and let me know.)

First, and most important, the mousetraps have to be glued down.  I think it might work to get small pieces of plywood and glue traps to them in sets of 20 or so.  Then the number of traps can be varied (see below) and the big plywood base isn’t going to move.  You can see one example of fixed traps here, but note the perfect reflector (see below).

But it gets worse.  Note from the video that the balls hitting the traps routinely knock the resting balls free without setting off the trap.  This is equivalent to the (n,3n) reaction cited above, which is quite rare.  Even the (n,2n) reaction is not common enough to sustain a chain reaction.  To make our model faithful, we need to stop this reaction.  Perhaps a small spot of glue could be used to fasten each ball to the trap.  The glue would have to be strong enough to hold when hit by another ping-pong ball, but the bond would have to be weak enough to allow the balls to go flying when the trap was tripped.  I think it would just require some experimenting with different types of glue.  If the hammer is steel, then perhaps a small magnet poked inside each ping-pong ball would be enough to hold it on and stop the (n,2n) reactions.  (I tested a Victor mouse trap.  The hammer looks to be copper but must be just copper coating over steel because the hammer is attracted by a magnet.)  The effects of having lots of magnetic ping-pong balls flying around might be interesting.

Note that in all the demonstrations, the traps are enclosed by walls (often mirrors to fool you into thinking there are more traps than there actually are).  This is equivalent to having a perfect neutron reflector, which doesn’t exist.  The height of the walls could be adjusted to show the effect of having some balls escape.

Ironically, the more energetic balls are good analogs for the slowest neutrons.  By flying high, they come down with the greatest force and are more likely to “induce a fission,” that is, set off a trap, just as slow neutrons have a greater likelihood, described by a larger “cross-section,” of inducing a fission.  In addition, by flying high, they take a long time to come back down just as slow neutrons take longer to get from one nucleus to another.  So just lowering the walls of the cage has the effect of letting the slow neutrons out and keeping the fast neutrons in.  Hmmm, that doesn’t seem right.  Maybe we need to put holes in the sides rather than simply lower the walls or just make a picket fence, with slats and gaps between.

With leaky walls that allow some balls to escape, we will discover the mousetrap equivalent of a critical mass.  Below some number, mousetraps within a lower wall, the will not be able to sustain a chain reaction because each reaction will result in two new balls being released but if, on average, more than one ball escapes, then the reaction will die out.  That is, it will not “go critical.”  But by increasing the number of traps, just increasing the floor space covered by traps, we reduce the surface to volume ratio or, since this is really a two dimensional model, the circumference to area ratio, and the chain reaction should be sustaining because the probability is increased that any given ping-pong ball will induce another reaction before jumping over the wall.  This is how a gun-assembled nuclear bomb works, taking two masses of fissionable material and bringing them together quickly to form a mass large enough to sustain a chain reaction.

We could also show how criticality depends not just on the number of traps but on their density.  If we placed the traps, not side-by-side, but with some separation, then some of the balls would land between the traps and not set another trap off.  The ball would bounce and might bounce over the wall, being lost.  If balls bounced out frequently enough, the reaction would not be sustaining.  But the same number of traps, simply packed closer, could sustain a reaction.  (This is how an implosion bomb works, the amount of mass is constant but the compression increases the density.)

We could also demonstrate the difference between critical masses of different nuclei.  The critical mass of plutonium-239 is much less than uranium-235.  Why?  Two big reasons:  (1) When a plutonium nucleus splits, it emits slightly more neutrons on average than when a uranium nucleus does.  So we could load the traps with different numbers of ping-pong balls, some with two, some with only one.  A lower average number would represent uranium and a higher average would represent plutonium.  We would find that we need fewer traps loaded with more balls to sustain a chain reaction.  (2) A plutonium nucleus is more likely to be split by a neutron than a uranium nucleus is.  The part of the trap where you put the cheese is called the catch (I had to look that up, too).  Most traps have just a little metal tab for the cheese (I find peanut butter actually works better) but some traps have a larger plastic tab that the mouse can step on.  Such a tab would be equivalent to a larger neutron cross section.  We would find that fewer large-catch traps would be needed to sustain a reaction than small-catch traps, just as less plutonium is needed compared to uranium.

So there is some hope for the mousetrap analog but it would be a lot more work.  I suspect we will continue to see the simple mousetrap demonstrations and I will just pretend not to have all the above objections because I do think it is very cool.

If you really want to impress me, you could do all of the above using rat traps and billiard balls.  (But stand back.)

I hope our readers are not devastated by having a cherished childhood image crushed but we are, after all, the Federation of American Scientists and sworn to the relentless pursuit of truth.

So much for the holiday break.  Back to saving the world.

by Ivanka Barzashka and Ivan Oelrich

Our article “A Technical Evaluation of the Fordow Fuel Enrichment Plant” published in the Bulletin of the Atomic Scientists on November 23 and its technical appendix, an Issue Brief, “Calculating the Capacity of Fordow”, published on the FAS website, have sparked quite a discussion among the small community that follows the technical details of Iran’s program, most prominently by Joshua Pollack and friends on armscontrolwonk.com (on December 1 and December 6) and by David Albright and Paul Brannan at ISIS, who have dedicated two online reports (from November 30 and December 4) to critiquing our work. (more…)

Last week, my ace research assistant, Ivanka Bazashka, and I published in the Bulletin of Atomic Scientists an analysis of Iran’s recently revealed Fordow uranium enrichment facility, lying just north of Qom.  In summary, we concluded that the timing of the construction and announcement of the facility did not prove an Iranian intention to deceive the agency but certainly raises many troubling questions.  The facility is far too small for a commercial enrichment facility, raising additional serious concerns that it might be intended as a covert facility to produce highly enriched uranium (HEU) for weapons.  But we also argued that the facility is actually too small to be of great use to a weapons program.  A quite plausible explanation is that the facility was meant to be one of several covert enrichment facilities and simply the only one to be discovered.  We believe, however, that it is significant that the Iranians assured the agency that they “did not have any other nuclear facilities that were currently under construction or in operation that had not yet been declared to the Agency” because any additional facilities uncovered in the future will be almost impossible to explain innocently. This, however, does not preclude Iran from making a decision to construct new enrichment facilities in the future.

Well, in just a few days, things have changed.  We immediately got a lot of emails (some of them quite rude!) challenging our numbers.  The Bulletin does not allow for lots of technical detail and we could not put our calculation in the article.  So Ivanka and I have written an explanation of the derivation of our numbers.  It is the first of a new format for the FAS website, FAS Issue Briefs.  I expect that Hans, Matt, Nishal, and others will make good use of the format in the future.  You can see our calculations in Calculating the Capacity of Fordow.

We show in our Issue Brief that the oft-cited performance of the Iranian centrifuge is based, at best, on hearsay, and, at worst, circular citations.  Reporters get away all the time with citing “high level officials” and the like but analysts do not have that luxury.  The reason that we are discussing the Iranian enrichment program is because of grave, immediate policy implications.  This not just a question of when Iran might get the bomb, but should we take military action, should we go to war, and when.  Ivanka and I conclude that the approach most often taken for estimating Iranian performance is unreliable and will almost certainly overestimate their capabilities.  We demonstrate an alternative based on universally accepted, publicly available data.

In particular, we should be very wary of Iranian statements of their own capability.  If I said that the National Ignition Facility at Livermore National Laboratory was going to achieve break even laser fusion within a year and cited an interview with the director of NIF, everyone would laugh at me.  Statements by Iran about Iran’s capability should be taken with an equally large grain of salt.  The Iranians brag about their technological virtuosity, specifically that, in spite of sanctions, they are still able to enrich uranium.   It is obviously a matter of national pride.  But do they explain to their taxpayers that they are spending billions of dollars to struggle to reproduce technology that the Europeans left behind as obsolete a half century ago and even that they do inefficiently?  Our calculations, based on publicly available IAEA reports, shows that Iran is operating its centrifuges at 20-25% of what we might expect.

The second big change is Iran’s announcement of ten new future enrichment facilities.  We argued in our Bulletin article that it was significant that Iran told the IAEA that there were no undeclared facilities waiting to be discovered.  Ivanka was more skeptical, saying that this declaration meant little if the Iranians used their definition of when they were required to “declare.”  I thought it more significant because any future discovery would be impossible to portray as innocent.  On the other hand, we also said that the Fordow facililty did not make much sense except as part of a network of clandestine facilities.  Well, the Iranians helped resolve that question when a few days later they announced that they were going to build ten new enrichment facilities, probably similar to Fordow.  It is getting harder and harder to give Iran the benefit of the doubt.

By Hans M. Kristensen

North Korea’s news agency – Korean Central News Agency – apparently has issued a statement saying that “The Federation of American Scientists of the United States has confirmed (North) Korea as a nuclear weapon state.” According to a report in the Korea Herald, the statement said a FAS publication issued in November listed North Korea as among the nine countries that possess nuclear weapons.

It’s certainly curious that they would need our reaffirmation, but after two nuclear tests we feel it is safe to call North Korea a nuclear weapon state. However, the agency left out that our assessment comes with a huge caveat:

“We are not aware of credible information on how North Korea has weaponized its nuclear weapons capability, much less where those weapons are stored. We also take note that a recent U.S. Air Force intelligence report did not list any of North Korea’s ballistic missiles as nuclear-capable.”

In other words, two experimental nuclear test explosions don’t make a nuclear arsenal. That requires deliverable nuclear weapons, which we haven’t seen any signs of yet. Perhaps the next statement could explain what capability North Korea actually has to deliver nuclear weapons.

This publication was made possible by a grant from Carnegie Corporation of New York and Ploughshares Fund. The statements made and views expressed are solely the responsibility of the author.

Estimated Locations of Nuclear Weapons, 2009

Some 23,300 nuclear weapons are stored at 111 locations around the world

.The world’s approximately 23,300 nuclear weapons are stored at an estimated 111 locations in 14 countries, according to an overview produced by FAS and NRDC.

Nearly half of the weapons are operationally deployed with delivery systems capable of launching on short notice.

The overview is published in the Bulletin of the Atomic Scientists and includes the July 2009 START memorandum of understanding data. A previous version was included in the annual report from the International Panel of Fissile Materials published last month.

Saratov Nuclear Sites

More than 1,000 nuclear weapons surround Saratov.

Russia has an estimated 48 permanent nuclear weapon storage sites, of which more than half are on bases for operational forces. There are approximately 19 storage sites, of which about half are national-level storage facilities.  In addition, a significant number of temporary storage sites occasionally store nuclear weapons in transit between facilities.

This is a significant consolidation from the estimated 90 Russian sites ten years ago, and more than 500 sites before 1991.

Many of the Russian sites are in close proximity to each other and large populated areas.  One example is the Saratov area where the city is surrounded by a missile division, a strategic bomber base, and a national-level storage site with probably well over 1,000 nuclear warheads combined (Figure 2).

The United States stores its nuclear weapons at 21 locations in 13 states and five European countries.  This is a consolidation from the estimated 24 sites ten year ago, 50 at the end of the Cold War, and 164 in 1985 (see Figure 3).

B61 Nuclear Bombs in Storage

Approximately 50 B61 nuclear bombs inside an igloo at what might be Nellis Air Force Base in Nevada. Seventy-five igloos at Nellis store “one of the largest stockpile in the free world,” according to the U.S. Air Force, one of four central storage sites in the United States.

Europe has about the same number of nuclear weapon storage locations as the Continental United States, with weapons scattered across seven countries. This includes seven sites in France and four in Britain. Five non-nuclear NATO countries (Belgium, Germany, Italy, the Netherlands, and Turkey) still host U.S. nuclear weapons first deployed there during the Cold War.

We estimate that China has 8-14 facilities associated with nuclear weapons, most likely closer to the lower number, near bases with units that operate nuclear missiles or aircraft.  None of the weapons are believed to be fully operational but stored separate from delivery vehicles at sites controlled by the Central Military Commission.

Is There a Nuclear Weapons Storage Site on Hainan Island?

Where does China store nuclear warheads for its ballistic missile submarines?  The naval base near Julin on Hainan Island has extensive underground facilities.  An alternative to the base itself could potentially be a facility elsewhere on the island, such as Foluo Air Base where construction of an underground facility began five years before the first SSBN arrived at Hainan. Or are the weapons stored on the mainland?  Click image to enlarge.

Israel probably has about four nuclear sites, whereas the nuclear storage facilities in India and Pakistan are – despite many rumors – largely undetermined.  All three countries are thought to store warheads separate from delivery vehicles.

Despite two nuclear tests and many rumors, we are unaware of publicly available evidence that North Korea has operationalized its nuclear weapons capability.

Warhead concentrations vary greatly from country to country. With 13,000 warheads at 48 sites, Russian stores an average of 270 warheads at each location. The U.S. concentration is much higher with an average of 450 warheads at each location. These are averages, however, and in reality the distribution is thought to be much more uneven with some sites only storing tens of warheads.

Finally, a word of caution is in order: estimates such as these obviously come with a great deal of uncertainty, as we don’t have access to classified intelligence estimates. Based on publicly available information and our own assumptions we have nonetheless produced a best estimate that we hope will assist the public debate. Comments and suggestions are encouraged so we can adjust the overview in the future.

This publication was made possible by a grant from Carnegie Corporation of New York and Ploughshares Fund. The statements made and views expressed are solely the responsibility of the author.

China’s newest nuclear submarines are noisier than 1970s-era Soviet nuclear submarines.

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By Hans M. Kristensen

China’s new Jin-class ballistic missile submarine is noisier than the Russian Delta III-class submarines built more than 30 years ago, according to a report produced by the U.S. Navy’s Office of Naval Intelligence (ONI).

The report The People’s Liberation Army Navy: A Modern Navy With Chinese Characteristics, which was first posted on the FAS Secrecy News Blog and has since been removed from the ONI web site [but now back here; thanks Bruce], is to my knowledge the first official description made public of Chinese and Russian modern nuclear submarine noise levels.

Force Level

The report shows that China now has two Jin SSBNs, one of which is based at Hainan Island with the South Sea Fleet, along with two Type 093 Shang-class nuclear-powered attack submarines (SSN). The Jin was first described at Hainan in February 2008 and the two Shangs in September 2008. The second Jin SSBN is based at Jianggezhuang with the North Sea Fleet alongside the old Xia-class SSBN and four Han-class SSNs.

The report confirms the existence of the Type 095, a third-generation SSN intended to follow the Type 093 Shang-class. Five Type 095s are expected from around 2015. The Type-95 is estimated to be noisier than the Russian Akula I SSN built 20 years ago.

Missile Range

The ONI report states that the JL-2 sea-launched ballistic missile on the Jin SSBNs has a range of ~4,000 nautical miles (~7,400 km) “is capable of reaching the continental United States from Chinese littorals.” Not quite, unless Chinese littorals extend well into the Sea of Japan. Since the continental United States does not include Alaska and Hawaii, a warhead from a 7,400-km range JL-2 would fall into the sea about 800 km from Seattle. A JL-2 carrying penetration aids in addition to a warhead would presumably have a shorter range.

Julang-2 SLBM Range According to ONI

Although the ONI report states that the Julang-2 can target the Continental United States, the range estimate it provides is insufficient to reach the lower 48 states or Hawaii.

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Alaska would be in range if the JL-2 is launched from the very northern parts of Chinese waters, but Hawaii is out of range unless the missile is launched from a position close to South Korea or Japan. The U.S. Defense Department’s 2009 report to Congress on the Military Power of the People’s Republic of China also shows the range of the JL-2 to be insufficient to target the Continental United States or Hawaii from Chinese waters. The JL-2 instead appears to be a regional weapon with potential mission against Russia and India and U.S. bases in Guam and Japan.

Patrol Levels

The report also states that Chinese submarine patrols have “more than tripled” over the past few years, when compared to the historical levels of the last two decades.

That sounds like a lot, but given that the entire Chinese submarine fleet in those two decades in average conducted fewer than three patrols per year combined, a trippling doesn’t amout to a whole lot for a submarine fleet of 63 submarines. According to data obtained from ONI under FOIA, the patrol number in 2008 was 12.

Since only the most capable of the Chinese attack submarines presumably conduct these patrols away from Chinese waters – and since China has yet to send one of its ballistic missile submarines on patrol – that could mean one or two patrols per year per submarine.

Implications

The ONI report concludes that the Jin SSBN with the JL-2 SLBM gives the PLA Navy its first credible second-strike nuclear capability. The authors must mean in principle, because in a war such noisy submarines would presumably be highly vulnerabe to U.S. or Japanese anti-submarine warfare forces. (The noise level of China’s most modern diesel-electric submarines is another matter; ONI says some are comparable to Russian diesel-electric submarines).

That does raise an interesting question about the Chinese SSBN program: if Chinese leaders are so concerned about the vulnerability of their nuclear deterrent, why base a significant portion of it on a few noisy platforms and send them out to sea where they can be sunk by U.S. attack submarines in a war? And if Chinese planners know that the sea-based deterrent is much more vulnerable than its land-based deterrent, why do they waste money on the SSBN program?

The answer is probably a combination of national prestige and scenarios involving India or Russia that have less capable anti-submarine forces.

This publication was made possible by a grant from Carnegie Corporation of New York and Ploughshares Fund. The statements made and views expressed are solely the responsibility of the author.