Page van der LindenOn the “Urgency” of the B61 LEP

B61 computer simulation. Image credit: Sandia National Laboratory

Growing up in Albuquerque, New Mexico during the Cold War meant that I had a lot of friends whose parents worked at Sandia National Labs (SNL) doing “nuclear bomb things”, or whatever vague description they’d get out of their parents about what was paying the bills. Things are somewhat more transparent these days, of course. For example, without revealing anything classified, the lab and the NNSA regularly provide updates on various LEPs; this year, SNL revealed some specifics regarding their refurbishment work on the B61 mod 7 and 11.

Over the past year or so, the B61 has been a topic of interest for several reasons. For one thing, the B61 was a prominent star in the 2010 Nuclear Posture Review, which mentioned plans for “a full-scope B61 LEP study and follow-on activities”, as well as the intention to make the F-35 Joint Strike Fighter capable of carrying it.

The B61 also features significantly in the NNSA’s FY 2011 budget, as Kingston Reif explains over at the Nukes of Hazard blog. Reif draws a number of conclusions, particularly that the proposed LEP study will be “major”, and will be designed to streamline the different B61 mods into the B61 mod 12; if you want to get down in the weeds about the B61 mod 12 LEP and some of the background involved, check out Jeffrey’s post from 2008.

Regarding SNL’s role in B61 refurbishment, we can always count on John Fleck of the Albuquerque Journal to get some good tidbits. Recently, he interviewed Dr. Paul Hommert, the director of SNL. The interview itself doesn’t reveal all that much; it’s Fleck’s follow-up on his blog that should get some good wonk discussion going.

Fleck points out that in his July 15, 2010 testimony before the Senate Armed Services committee, Hommert said:

[W]e find ourselves in a state of urgency, with a demanding schedule and expansive product requirements. The primary driver for the schedule of the B61 LEP is the fact that critical nonnuclear components are exhibiting age-related performance degradation. For example, the radar in the B61, which includes the now infamous vacuum tubes, must be replaced. In addition, both the neutron generator and a battery component are fast approaching obsolescence and must be replaced. A secondary driver for the schedule is the deployment of the F35 Joint Strike Fighter, which requires a new digital interface for the B61. Replacing the three aging components and adding the new digital interface represent the absolute minimum approach to this LEP. However, it is my judgment that we need to approach this LEP with a resolute commitment to replace old nonnuclear components and field a nuclear weapon system that employs modern technologies to improve safety and security and to extend service life.

(Bold emphasis mine.)

Fleck then shares with us what SNL’s former Vice President of Technical Support,Bob Peurifoy, told him via email, on the record:

Regarding radars: The B61 Mod 7 used to use a vacuum tube radar. As of my last interaction with Sandia, that vacuum tube radar was showing no aging problems. Something must have changed. During the Mod 7 production run, vacuum tubes became scarce, and I believe the B61 Mod 7 adapted the B83 solid state radar. As I recall, the solid state radar was not age-stable, and at least one retrofit was necessary.

Neutron generators contain tritium. Tritium undergoes radioactive decay, with a half-life of about 12.5 years. It has been necessary, therefore, to replace neutron generators periodically during scheduled maintenance. This is not something new and used to be planned for. No sense of urgency there.

Regarding a ‘battery component’: when I left Sandia, thermal batteries, by all accelerated aging tests, had an infinite life. Hommert’s use of the term “battery component” may refer to an RTG used in the B61 Mod 3 and 4. The RTG used plutonium-238 as a heat source. Its anticipated life was about 25 years. This has been known since 1979. Again, I don’t understand the use of “sense of urgency.”

Being skeptical of the design labs’ management integrity, I’m suspicious that the real reason for the “urgency” is budget-related.

So, this all leads to the question: how “urgent” are the problems that Hommert lists? Obviously, Peurifoy thinks that Hommert is overstating the case as part of a bid for, shall we say, “nuclear pork”. Were these problems there all along and weren’t remedied, so they actually are urgent, or is Peurifoy on the right track here?

Let’s do some brainstorming. What do you think?


  1. John Schilling (History)

    Particularly with regards to the radar, I will refer to George Herbert’s comment over in the “M word” thread. If it’s outside the physics package, I don’t really care any more than I would if someone proposed redesigning the dome light on a B-52 because the old bulbs were no longer available. Except, that is, to the extent that other people will deliberately exploit confusion on this point for their own ends.

    There are nuclear physics packages, and there is hardware that’s used to arrange for a nuclear physics package to do its thing where we (hypothetically) want it to. There are in some contexts legitimate reasons to draw a line that encompasses all of the former and some of the latter and say “everything inside here is a ‘warhead’, the rest is a ‘missile'”. Or bomb/airplane, whatever.

    In the nonproliferation context, I’d prefer to draw the line around the physics package – delivery hardware is of course going to be maintained and modified and upgraded,
    and this will at times reach the level of urgency. This should not be controversial. This also should not be used to bamboozle people into agreeing to physics-package work without their explicit knowledge and approval. Nor should it be used to frighten anyone into thinking those darned mad scientists are building bombs again.

    Whether the radar really needs to be replaced this year or could wait another decade, whether the guy in the radar shop is just angling for his share of pork, is mostly just a distraction from what we really care about.

  2. Eric Palmer (History)

    We probably have to develop a business case for clearing a nuke store for the F-35 in the first place. Is this really even needed? Important as the F-35 won’t be able to stand up to high end threats over its supposed life.

    The following should be considered when looking at the topic of F-35 survivability.

  3. yousaf (History)

    Bob Peurifoy is correct, of course. There is no urgency in any of this business.

    Since the mid-1940s nukes have been used for deterrence purposes. Any alleged urgency would only come about if there were well-known (i.e. to our nuclear enemies, whoever they may be) failure modes that would render the devices essentially useless (not just sub-optimal), and thus make the B61’s deterrent value un-scary. As most rational people would err on the side of considering the B61s scary in their current state, their deterrent value is intact and there cannot be any urgency — unless an urgent nuclear conflict (for which the other warhead types are somehow insufficient) is forseen.

    I’m for the LEP but let’s not pretend that this is urgent.

    The budgetary urgency is likely the actual motivation here.

  4. Henry J Cobb (History)

    Aus Air Power is not a very good source on anything.

    For example they overlook the F-35’s EOTS which will be vital in the use of the future B61 “J-DAM(N)”. Use a conventional weapon to punch a hole in some bunker door, use the EOTS to determine the exact coordinates of the hole and drop an improved guidance B61 through the hole while the F-35 uses its afterburner to get some of the bulk of the Earth between itself and ground zero.

    No other aircraft can do this mission while maintaining stealth. Hence the urgency of delivering it to Israel ASAP.

    • John Schilling (History)

      First, I think you rather overestimate the utility of “punching a hole in some bunker door”. We already have the B61-11, which can punch its own hole in the overlaying rock, detonating maybe three meters down and pulverizing everything within two or three hundred meters. If that’s not enough, then you’re not dealing with a bunker that has a door, but a tunnel complex with many doors.

      Second, I seriously question the urgency of giving Israel stealthy precision-guided thermonuclear weapons. Israel already has a perfectly good deterrent; what you propose is good only for jump-starting World War III. In the unlikely event that bombing Iran turns out to be necessary and appropriate, the United States can do the job better than Israel – indeed, about the only thing Israel can do is bomb Iran just enough to make it necessary for the United States to finish the job, and I for one would prefer that decision be made in Washington than Jerusalem.

      And, more generally, it sounds like you are buying into the scenario of a “clean” nuclear strike, where the bomb detonates underground and a bunker is destroyed while there’s only some shaking and a bit of dust kicked up on the surface. Doesn’t work that way; you’re still going to get the crater and the mushroom cloud and the fallout plume. With CNN showing enough high-definition corpses to overflow the biggest television screens.

      I strongly recommend the National Research Council’s “Effects of Nuclear Earth-Penetrator and Other Weapons” in this context. There are specialized applications where adding precision guidance to a B61-11 would be useful, but it’s not a panacea and it’s not particularly urgent. If we’ve got a crew of nuclear-weapons engineers that we are going to need for life-extension work in five years but are idle today, sure, let them work on this one now. If, as Hommert claims, the life-extension work is presently urgent, the precision-guided H-bombs can wait.

      If the plan is to fund everything on everyone’s wish list right away, then figure out what we’re going to pay for to keep everyone busy when they’ve delivered everything we presently want, then no.

  5. Ed Gaffney (History)

    Simple arithmetic (2010-25=1985) indicates the urgency. These things should have been replaced 6 years ago.

    • FSB (History)

      What does your arithmetic refer to, pray tell? The RTG?

      What “things” should have been replaced 6 years ago?

      If no one has nuclear bombed us in those 6 years, looks like there is not much urgency.

      The job of nuclear weapons is to appear scary to other political leaders, as mentioned above.

      I also concur with Peurifoy 100%.

  6. Allen Thomson (History)

    > JDAM

    Not to get too far off into the weeds, but I have wondered why the US hasn’t developed a JDAMized B61. Precision delivery might allow selection of lower yields in some cases and, since a JDAM is also a kind of glide bomb, the delivery options would be much increased. See slide 9 in .

  7. weaponeer (History)

    Six blind men were discussing exactly what they believed an elephant to be, since each had heard how strange the creature was, yet none had ever seen one before. So the blind men agreed to find an elephant and discover what the animal was really like.

    It didn’t take the blind men long to find an elephant at a nearby market.

    1. The first blind man approached the beast and felt the animal’s firm flat side. “It seems to me that the elephant is just like a wall,” he said to his friends.

    2. The second blind man reached out and touched one of the elephant’s tusks. “No, this is round and smooth and sharp – the elephant is like a spear.”

    3. Intrigued, the third blind man stepped up to the elephant and touched its trunk. “Well, I can’t agree with either of you; I feel a squirming writhing thing – surely the elephant is just like a snake.”

    4. The fourth blind man was of course by now quite puzzled. So he reached out, and felt the elephant’s leg. “You are all talking complete nonsense,” he said, “because clearly the elephant is just like a tree.”

    5. Utterly confused, the fifth blind man stepped forward and grabbed one of the elephant’s ears. “You must all be mad – an elephant is exactly like a fan.”

    6. Duly, the sixth man approached, and, holding the beast’s tail, disagreed again. “It’s nothing like any of your descriptions – the elephant is just like a rope.”

    And all six blind men continued to argue, based on their own particular experiences, as to what they thought an elephant was like. It was an argument that they were never able to resolve. Each of them was concerned only with their own idea. None of them had the full picture, and none could see any of the other’s point of view. Each man saw the elephant as something quite different, and while in part each blind man was right, none was wholly correct.

    • FSB (History)

      While the 6 blind mice were examining the elephant diligently, others were adopting an arrogant attitude and not contributing constructively to the debate by posting irrelevant anecdotes on-line.

    • Paul (History)

      Bob Peurifoy is one of the very few who has the background and has seen all sides of the elephant.

  8. Allen Thomson (History)

    > strongly recommend the National Research Council’s “Effects of Nuclear Earth-Penetrator and Other Weapons” in this context.

    Me too:

    Bottom line: earth penetrating bombs can’t penetrate deeply enough that a nuclear weapon with meaningful yield would produce a contained explosion. Hence, surface effects and fallout.

    Should be on the bookshelf of all wonks.

    (Of only slight relevance — considerably deeper depth of burst, probably of somewhat greater yield than we’re talking about — see )

  9. Robert Merkel (History)

    Let’s assume for the moment – contrary to the evidence in the public domain – that a nuclear strike could be carried out on a deeply buried target without causing significant surface effects. Let’s furthermore accept that the strike could not have been feasibly carried out by a conventional weapon.

    Even in those circumstances and even putting taking as “realist” a perspective as I can, it is *very* hard to imagine a situation where the geopolitical risks of such a nuclear strike outweigh the potential gains.

    American alliances around the world would be thrown into absolute chaos.

    More generally, I cannot see *any* plausible justification for F-35’s to carry nuclear weapons, earth-penetrating or otherwise. The USA has multiple missile-based means by which nuclear weapons can be reliably delivered anywhere on Earth.

    As for Israel, why any sane country would wish to assist them to a nuclear capability specifically for offensive war (as distinct from a nuclear deterrent, which they’ve had for decades) is completely and utterly beyond me.

    • John Schilling (History)

      The United States does not have any missile-based means by which nuclear weapons can be effectively deployed against targets buried more than 250 meters deep, whereas aircraft equipped with the B61-11 can effectively engage targets down to perhaps 400 meters.

      The United States does not have any missile-based means by which targets more than 50-100 meters deep can be destroyed with anything less than a 300-kiloton groundburst. The postulated B61-11/JDAM could engage targets down to 150 meters with a 10-kiloton yield setting. Yes, vented to atmosphere with all the devastation and contamination that implies, but ten kilotons’ worth rather than three hundred. The neighbors will appreciate the concern.

      And the United States does not have any missile-based means by which nuclear weapons can be delivered with the reliable opportunity to have a pair of human eyes observe the target and note, e.g., that there are an awful lot of unarmed civilian protesters marching on ground zero and maybe we ought to rethink this whole plan.

      There is still a legitimate case, including but not limited to the above scenarios, for direct aircraft delivery of nuclear weapons. It is probably unwise to place that responsibility entirely on the 20 remaining B-20 bombers, and in the long term a shift from say B-2 + F-15E to B-2 + F-35 would be reasonable. As would adding precision guidance capability to the B-61.

      Reasonable, but not in any way urgent. It is as you say hard to imagine (actually, easy to imagine but unlikely to manifest in reality) situations where such a capability would be needed, and none seem to be on the immediate horizon.

    • George William Herbert (History)

      Generally agreeing with John. However, there was little apparent logic behind a television guided Sparrow missile, and we saw those used in Desert Storm and possibly elsewhere as golden BB weapons. I don’t know if doing a kit like that for a B61 could be done without it getting out via Congress, but I can imagine someone saying “Let’s just go make 10 of these, just in case…”

      Probably not a big engineering deal. Probably a variant of the 1,000 lb bomb JDAM kit, with a new strakes set would do nicely. But who knows if one actually exists. Lots of things could exist… look at how the GBU-28 came about, after all… but a lot of potential ones never get off the PowerPoint slide they were presented on.

  10. Robert Merkel (History)

    Silly question, but how does fallout scale with yield, assuming everything else is equal?

    My understanding was that fallout is essentially the result of the fission products; as such, a 10 kt yield from the primary wouldn’t necessarily be all that much cleaner than a larger yield coming from a fusion secondary.

    • John Schilling (History)

      As Allen Thompson indicated, modern thermonuclear weapons seem to have approximately 50% fission yield. You need a dense metal to serve as the tamper for the secondary, you’ve got lots of depleted and maybe some semi-enriched uranium left over from making the primary, and if you use that as the tamper it will double the yield as it fissions in that nice hot 14-MeV neutron flux.

      And let’s not forget the whole Earth-Shattering Kaboom aspect of nuclear weaponry. If you live in a town 1-3 miles away from a 10-kiloton groundburst, you can probably evacuate ahead of the fallout. If your town is 1-3 miles from even a hypothetical pure-fusion 300-kiloton groundburst, you’re probably dead or dying a few seconds later.

      How many civilians live within the 1-3 mile zone of e.g. North Korea’s deeply-buried C3I and WMD facilities I do not know and wouldn’t care to guess, but it’s probably not zero and those are lives that can be saved by using smart rather than dumb nuclear bombs if it comes to that.

    • kme (History)

      That tertiary fissioning of the tamper and/or bomb case is why the Castle Bravo test ended up having a yield more than 3 times what was planned.

  11. Allen Thomson (History)

    “My understanding was that fallout is essentially the result of the fission products; as such, a 10 kt yield from the primary wouldn’t necessarily be all that much cleaner than a larger yield coming from a fusion secondary.”

    True, but there are indications that modern US secondaries contain a good deal of fallout-producing U235.

  12. terajoule (History)


    FSB doesn’t like Weaponeers because their judgment is clouded by their experience.

    • FSB (History)

      No, I don’t like arrogant irrelevant anecdotes with no technical merit — at the very least make the irrelevant anecdotes interesting, or throw some obscenities in or whatever.

      Probably, some weaponeers don’t like to be told that what they are working on is not really urgent. Truth hurts.

      As I said, I agree with real weaponeers like Bob Peurifoy.

    • Not a Wonk (History)

      Bob Peurifoy retired from Sandia National Laboratories ay back in 1991. A lot of change has occurred in Nuclear Weapons since he has left, including Science-Based Stockpile Stewardship and the development of Life Extension Programs instead of weapon system replacement. The issues that the Nuclear Weapons Enterprise are dealing with now are not the same as when Dr. Peurifoy was in the business. As time marches on, his “insights” have decreasing relevance.

    • FSB (History)

      You do not offer any technical counter-argument to what Dr. Peurifoy says — you only say, effectively that he is old. There are many smart old weaponeers. In fact, the older ones I know have MUCH better insight than the newer ones.


      The fact that we now have a super-duper science based stewardship program and other crap you mention does not detract from the fact that post-Cold War we are not in a situation where we urgently need to use one type of nuclear weapon.

      As Bob said, there is no urgency in the B61 LEP. Let’s do it, but it is not urgent, OK?

      See comments by other posters above why this is so (eg. comment by Yousaf).

      Unless you can tell me why there is urgency to do this, how about stopping the ad hominems?

  13. Sean O'Quin (History)

    Lets look at the issue from a pure force support and political perspective:

    1. A refresh to protect the troops from IED’s and insurgent warfare tactics is an urgent allocation
    2. There must be a modification in the protocols of the United States to switch to use of nuclear weapons as offensive means for bunker busting. There are capabilities on hand to manage all existing requirements using conventional means.

    I agree with John Shilling’s assessment on sharing the aircraft borne delivery deterrence and the F35 may be the correct secondary platform but by no means justify a “state of urgency”.

    After a second reading of Hommert’s testimony the following quote stuck out to:

    “To extend the lifetime of the B61, the requested FY 2011 funding is critical. We must complete
    the design definition in FY 2011 to create a firm understanding of system requirements and thus
    fully establish future-year budget needs. Total cost estimates for the B61 LEP are subject to change
    until the design definition and requirements are finalized.”

    Is he stating that design definition is open to the point where the scope, cost and program schedule would need to be left so wide open? I think that a summary review of the key tasks should be presented before any allocation is finalized. That is how it happens in the real world!

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