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  • Polyanna Pinker’s Power Profundities

    Posted on October 10th, 2018 Helian No comments

    Recently Steven Pinker, public intellectual and author of a “history” of the Blank Slate debacle that was largely a fairy tale but at least drew attention to the fact that it happened, has been dabbling in something entirely different. Inspired by the latest UN Jeremiad against climate change, he has embraced nuclear power. In a series of tweets, he has endorsed articles advocating expanded reliance on nuclear power, such as one that recently turned up at Huffpo cleverly entitled “If We’re Going To Save the Planet, We’ve Got To Use the Nuclear Option.” As things now stand, that would be a dangerous, wasteful, and generally ill-advised idea.

    I say “as things now stand.” I’m certainly not opposed to nuclear power. I’m just opposed to the way it would be implemented if we suddenly decided to build a bevy of new nukes given current economic realities.  The new reactors would probably look like the AP1000 models recently abandoned in South Carolina. Such reactors would use only a fraction of the available energy in their nuclear fuel, and would produce far larger amounts of long-lived radioactive waste than necessary. They are, however, cheaper than alternatives that could avoid both problems using proven technologies. Given the small number of players capable of coming up with the capital necessary to build even these inferior reactors, there is little chance that more rational alternatives will be chosen until alternative sources of energy become a great deal more expensive, or government steps in to subsidize them. Until that happens, we are better off doing without new nuclear reactors.

    As noted above, the reasons for this have to do with the efficient utilization of nuclear fuel, and the generation of radioactive waste.  In nature there is only one potential nuclear fuel – Uranium 235, or U235. U235 is “fissile,” meaning it may fission if it encounters a neutron no matter how slow that neutron happens to be traveling.  As a result, it can sustain a nuclear chain reaction, which is the source of nuclear energy. Unfortunately, natural uranium consists of only 0.7 percent U235. The rest is a heavier isotope – U238. U238 is “fissionable.” In other words, it will fission, but only if it is struck by a very energetic neutron. It cannot sustain a fission chain reaction by itself.  However, if U238 absorbs a neutron, it becomes the isotope U239, which quickly decays to neptunium 239, which, in turn, quickly decays to plutonium 239. Plutonium 239 is fissile. It follows that if all the U238 in natural uranium could be converted to Pu239 in this way, it could release vastly more energy than the tiny amount of U235 alone. This is not possible in conventional reactors such as the AP1000 mentioned above. A certain amount of plutonium is produced and burned in the fuel elements of such reactors, but the amount is very small compared to the amount of available U238. In addition, other transuranic elements, such as americium and curium, which are produced in such reactors, along with various isotopes of plutonium, would remain dangerously radioactive for thousands of years.

    These problems could be avoided by building fast breeder reactors. In conventional reactors, neutrons are “thermalized” to low energies, where the probability that they will react with a fuel nucleus are greatly increased. The neutron spectrum in “fast” reactors is significantly hotter but, as a result, more neutrons are produced, on average, in each encounter. More neutrons means that more Pu239 can be produced without quenching the fission chain reaction.  It also means that the dangerous transuranic elements referred to above, as well as long lived fission products that are the source of the most long-lived and dangerous radioactive isotopes in nuclear waste, could be destroyed via fission or transmutation. As a result, the residual radioactivity resulting from running such a nuclear reactor for, say 30 years, would drop below that released into the environment by a coal plant of comparable size in 300 to 500 years, as opposed to the thousands of years it would take for conventional reactors. And, yes, radioactivity is released by coal plants, because coal contains several parts per million each of radioactive uranium and thorium.  Meanwhile, a far higher percentage of the U238 in natural uranium would be converted to Pu239, resulting in a far more efficient utilization of the fuel material.

    An even better alternative might be molten salt reactors. In such reactors, the critical mass would be in liquid form, and would include thorium 232 (Th232) in addition to a fissile isotope.  When Th232 absorbs a neutron, it decays into U233, another fissile material.  Such reactors could run at a lower neutron “temperature” than plutonium breeders, and would be easier to control as a result.  The liquid core would also greatly reduce the danger of a nuclear accident. If it became too hot, it could simply be decanted into a holding pan where it would immediately become subcritical. Thorium is more abundant than uranium in nature, so the “fuel” material would be cheaper.

    Consider the above in the context of the present. Instead of extracting the vast amounts of energy locked up in U238, or “depleted” uranium, we use it for tank armor and armor piercing munitions. In addition to this incredibly stupid waste of potentially vast energy resources, we dispose of huge amounts of it as “radioactive waste.”  Instead of treasuring our huge stores of plutonium as sources of carbon-free energy, we busy ourselves thinking up clever ways to render them “safe” for burial in waste dumps.  It won’t work.  Plutonium can never be made “safe” in this way. Pu239 has a half-live of about 25,000 years.  It will always be possible to extract it chemically from whatever material we choose to mix it with.  Even if it is “reactor grade,” including other isotopes of plutonium such as Pu240, it will still be extremely dangerous – difficult to make into a bomb, to be sure, but easy to assemble into a critical mass that could potentially result in radioactive contamination of large areas. Carefully monitored breeder reactors are the only way of avoiding these problems.

    According to the Huffpo article referenced above,

    Doesn’t nuclear power contribute to nuclear weapons proliferation? No. Weapons programs do not depend on civilian nuclear power, which operates under stringent international safeguards.

    Really? Will the “stringent international safeguards” last for the 25,000 years it takes for even half the plutonium waste produced by conventional reactors to decay? I would advise anyone who thinks it is impossible to fabricate this waste into a bomb, no matter what combination of isotopes it contains, to take an elementary course in nuclear engineering. The only way to avoid this problem is to burn all the plutonium in breeder reactors.  Predictably, the article doesn’t even mention the incredible wastefulness of current reactors, or the existence of breeder technology.

    It’s nice that a few leftist “progressives” have finally noticed that their narrative on nuclear power has been controlled by imbeciles for the last half a century. I heartily concur that nuclear energy is a potent tool for reducing carbon and other greenhouse gas emissions.  I simply suggest that, if we decide to return to nuclear, we either provide the subsidies necessary to implement rational nuclear technologies now, or wait until it becomes economically feasible to implement them.

  • No, We Don’t Need to Resume Nuclear Testing

    Posted on August 11th, 2018 Helian No comments

    According to an article entitled In Alarming New Study, Nuclear Lab Scientists Question U.S. Weapons’ Performance that recently appeared in Investor’s Business Daily, a couple of Los Alamos scientists have released a report questioning the reliability of the U.S. nuclear arsenal, and calling for a resumption of nuclear testing.  It would be a bad idea.  Let me explain why.

    The two scientists claim that the reliability of the aging weapons in our arsenal will become increasingly questionable as the number of years since their “best if used by” date increases.  They base their argument largely on uncertainties about whether computer codes will be able to accurately predict the performance of these aging weapons.  It’s true that computer codes have not always been perfectly accurate in predicting the outcome of complex physical processes.  However, the significance of that fact must be weighed in the context of how it affects all the nuclear powers, not just the United States.  In the absence of nuclear testing, we all have the same problem.  The relevant question, then, is not whether the problem exists, but how severely it impacts us compared to the other nuclear states.  We have conducted more nuclear tests than any other country, and therefore have a much larger database than our competitors with which to compare code predictions.  When it comes to computer codes, that gives us a very significant advantage as long as the moratorium on testing continues.  That advantage will become a great deal less significant if testing is resumed.

    However, computer codes are not the only means we have of assessing the reliability of the weapons in our arsenal.  The U.S. also has an unmatched advantage in terms of experimental facilities that are able to access physical conditions relevant to those that occur in nuclear weapons.  For example, these include the Z machine at Sandia National Laboratories, which is capable of producing a far more powerful burst of x-rays in the laboratory than any competitor, and the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, which can dump a huge amount of energy in a tiny target in a very short time.  Such facilities can access extreme material densities and temperatures, enabling a host of experiments in weapon physics and weapon effects that are currently beyond the capabilities of any other country.  If we resume testing we will be throwing this advantage out the window as well.  In short, we may have our problems when it comes to assessing the reliability of the weapons in our arsenal, but the problems faced by our potential competitors are even worse.  Under the circumstances, it makes little sense to do something as destabilizing as rocking the nuclear boat.

    If we are really worried about the reliability of our arsenal, we should seriously consider adding another experimental facility to go along with Z, NIF, and the rest.  I refer to what is known as an Advanced Hydrodynamic Facility, or AHF.  We seriously considered building such a facility back in the late 90’s, but have pretty much forgotten about it since then.  Basically, the AHF would be a very powerful particle accelerator, capable of delivering beams of energy so penetrating that they could image the critical, high-explosive driven implosion process in nuclear weapons in its entirety in three dimensions.  Obviously, it would be necessary to replace the nuclear materials used in real weapons with suitable surrogates, but this would introduce very little uncertainly in the experimental results.  An AHF would not only add to our existing advantage over other nuclear states as long as the test moratorium continues, but would effectively lay to rest any remaining uncertainties not resolved by the computer codes and experimental facilities we already have.

    I can understand the eagerness of weapon scientists to resume nuclear testing.  It would make their lives a lot more interesting.  However, it would hardly be to the advantage of the rest of us.  I suggest that, instead of unilaterally taking such a foolhardy step, we maintain and expand the advantage we already have and will continue to enjoy as long as the test moratorium continues.

  • Whither Nuclear Power? A Few Comments on Thorium and the End of the “Nuclear Renaissance”

    Posted on September 2nd, 2017 Helian No comments

    About a decade ago there was much talk of a “nuclear renaissance” amid concerns about greenhouse gas emissions and the increasing cost of fossil fuel alternatives.  The Nuclear Regulatory Commission received applications to build no less than 31 new nuclear plants as the price of crude oil spiked to over $140 per barrel.  Now, however, with last month’s decision by SCANA Corp. to abandon the V. C. Summer project, a pair of nukes that had been under construction in South Carolina, nuclear’s future prospects look dim, at least in the United States.  Two plants remain under construction in Georgia but, like the ones abandoned in South Carolina, they are to be AP1000s, designed by Westinghouse.  Westinghouse filed for bankruptcy in March.  Delays and massive cost overruns similar to those that led to the demise of V. C. Summer also afflict the Georgia project, and its future seems doubtful at best.

    In short, the dream of a nuclear renaissance has evaporated.  For the time being, at least, nuclear in the U.S. is no match for more agile competitors like wind, solar, and natural gas.  However, there may be a silver lining to this cloud.  Plants like Westinghouse’s AP1000 waste most of the energy in their nuclear fuel, creating massive amounts of avoidable radioactive waste in the process.  To the extent that it makes sense to build nuclear plants at all, these are not the kind we should be building.  To understand why this is true it is first necessary to acquire some elementary knowledge about nuclear physics.

    The source of the energy produced in the core of nuclear reactors is a nuclear fission chain reaction.  Only one material that exists in significant quantities in nature can sustain such a chain reaction – uranium 235, or U235.  U235 is an isotope of uranium.  Isotopes of a given element consist of atoms with the same number of positively charged protons in their central core, or nucleus.  Like all other isotopes of uranium, U235 has 92.  There are also 143 neutrally charged neutrons, making a total of 235 “nucleons.”  Natural uranium consists of only about 0.7 percent U235.  Almost all the rest is a different isotope, U238, with a nucleus containing 146 neutrons instead of 143.

    When we say that U235 can sustain a nuclear chain reaction, we mean that if a free neutron happens to come within a very short distance of its nucleus, it may be captured, releasing enough energy in the process to cause the nucleus to split into two fragments.  When this happens, more free neutrons are released, that can then be captured by other uranium nuclei, which, in turn, fission, releasing yet more neutrons, and so on.  As noted above, U235 is the only naturally occurring isotope that can sustain such a nuclear chain reaction.  However, other isotopes can be created artificially that can do so as well.  The most important of these are U233 and plutonium 239, or Pu239.  They are important because it is possible to “breed” them in properly designed nuclear reactors, potentially producing more usable fuel than the reactor consumes.  U233 is produced by the reactions following absorption of a neutron by thorium 232, or Th232, and Pu239 by those following the absorption of a neutron by U238.  In other words, we know of three practical types of nuclear fuel; U235, U233 and Pu239.  The first occurs naturally, and the other two can be readily “bred” artificially in nuclear reactors.

    Let’s consider what this means in the case of conventional nuclear reactors like the Westinghouse AP1000.  These are powered by fuel elements that typically are enriched in U235 from the naturally occurring 0.7 percent to from three to five percent.  The remaining 95 to 97 percent of the uranium in these fuel elements is U238.  When the fission process starts, some of the neutrons released are captured by the U238, eventually resulting in the production of Pu239.  Some of this plutonium fissions along with the U235, contributing to the total energy produced by the fuel elements.  However, only a small fraction of the U238 is converted to Pu239 in this way before the fuel is consumed and it becomes necessary to replace the old fuel elements with fresh ones.  In addition to a great deal of U238, these spent fuel elements contain a significant amount of plutonium, as well as other transuranic elements such as americium and curium, which can remain dangerously radioactive for thousands of years.  The “waste” plutonium might even be used to produce a nuclear weapon.

    Obviously, if possible it would be better to extract all the energy locked up in natural uranium rather than just a small fraction of it.  In fact, it is possible, or very nearly so.  Breeder reactors are feasible that could burn nearly all the U238 in natural uranium as well as the U235 by converting it into Pu239.  In the process they could destroy much of the transuranic waste that is the main source of radioactive danger from spent fuel.  In as little as 500 years the residual radioactivity from running a nuclear plant for 30 years could potentially be less than that of the original naturally occurring uranium.  Unfortunately, while all this is scientifically feasible, it is not economically feasible.  It won’t happen without massive government subsidies.  Perhaps such subsidies are warranted in view of the threat of climate change and perhaps not, but, regardless, breeder reactors won’t be built without them.  Since they are really the only types of reactors it makes sense to build, we would probably be better off, at least for the time being, building no reactors at all.  That’s the “silver lining” I referred to above.  Perhaps a time will come when the world runs out of expendable sources of base load electrical power, such as oil, coal and natural gas, and no way has been found to take up the slack with renewables.  In that case, it may once again make economic sense to build breeder reactors.  Until that time, the United States would do well to build up a healthy stockpile of uranium, and put a stop to the stupid, wasteful, and counterproductive use of depleted uranium that could potentially become a source of vast amounts of energy to produce munitions and armor.

    But wait, there’s more!  What about thorium?  Thorium by itself can’t sustain a nuclear chain reaction.  It can, however, be converted into U233 by neutron absorption, and that is an ideal reactor fuel.  Among other things, it generates more neutrons per fission at lower neutron “temperatures” than either Pu239 or U235.  That means that extra neutrons are available to “breed” fuel at those lower temperatures where nuclear reactors are easier to control.  By “temperature” here, we’re referring to the average speed of the neutrons.  The slower they are, the more likely they are to be absorbed by a nucleus and cause fission reactions.  Neutrons are slowed in “moderators,” which can be any number of light types of atoms.  The most common is plain water, consisting of the elements hydrogen and oxygen.  Think of a billiard ball hitting another billiard ball head on.  It comes to a complete stop, transferring its energy to the other ball.  The same thing can happen with neutrons and the proton nucleus of hydrogen atoms, which are of approximately equal mass.  To breed plutonium effectively, reactors must be run at significantly higher neutron temperatures.

    There’s more good news about thorium.  It can be dissolved in various exotic mixtures and breed U233 in a reactor with a liquid instead of a solid core.  This would have a number of advantages.  In the first place, a “meltdown” would be impossible in a core that’s already “melted.”  If the core became too “hot” it could simply be drained into a holding pan to form a subcritical mass that would quickly cool.  It would also be possible to extract waste fission products and introduce fresh fuel, etc., into the core “on the fly.”  As a result the reactor would be able to stay in operation longer between shutdowns for maintenance and refueling.  The necessary technology has already been demonstrated at places like Oak Ridge, Tennessee and Shippingport, Pennsylvania.  Recently, a Dutch team finally began experiments with molten salt technology intended to take up where these earlier experiments left off after a hiatus of more than 40 years.

    Perhaps thorium’s biggest problem is the tendency of its proponents to over-hype its promise.  It even has a founding myth based on bogus claims that thorium technology isn’t dominant in the energy industry today because “it’s much harder to weaponize.”  For example, according to the article about the Dutch experiments linked above, entitled, ‘Safer’ thorium reactor trials could salvage nuclear power,

    But, if it’s so safe and reliable why hasn’t thorium been used all along? Because (unlike uranium) it’s much harder to weaponize. As a result, it’s historically been sidelined by nations in search of both energy and a potential source of weapons-grade plutonium.

    This yarn about a benign source of energy that might have benefited all mankind being torpedoed by evil weaponeers might sound good, but it’s complete nonsense.  Thorium itself can’t be weaponized, because it can’t sustain a nuclear chain reaction on its own.  The sole reason there’s any interest in it at all as a source of nuclear power is the possibility of transmuting it to U233.  Of course, it can’t be used to produce weapons-grade plutonium.  However, there is no better material for making nuclear bombs than U233.  As is the case with Pu239, four kilograms is sufficient to make a nuclear weapon, compared to the 25 kilograms that is a sufficient quantity of U235.  It’s main drawback as a weapons material is the fact that small amounts of U232 are produced along with it in thorium-based reactors, and U232 decays into radioactive daughters that are deadly sources of powerful gamma rays.  However, the amount of U232 produced can be reduced dramatically by cooling the neutron spectrum to a low “temperature.”  In short, thorium could definitely be used to make weapons.  The reason it isn’t the dominant technology for that purpose is the same as the reason it isn’t the dominant technology for producing electric power; it would be significantly more complex and expensive than using natural or slightly enriched uranium as a fuel.  That reason is as valid now as it was in the days of Little Boy and Fat Man.  The “dominant technology” would be the same as it is today whether nuclear weapons had ever been produced or not.

    When it comes to the technology itself, thorium proponents also tend to be coy about mentioning problems that don’t afflict other reactor types.  For example, the materials needed for practical molten salt reactors are extremely corrosive.  There has been progress towards finding a metal that can hold them, but no ideal alloy has yet been found.  This isn’t necessarily a show stopper, but it’s not an insignificant problem, either.  Such material issues have been largely solved for conventional reactors.  If, as would seem to be the case, these are no longer economically competitive with their rivals, then molten salt is pretty much out of the question, at least for the time being.  It’s important to point out that, if breeder reactors ever do become economically feasible again, it will always be necessary to insure that they are secure, and that the materials they produce can’t be diverted for making weapons.  That concern applies to both plutonium and thorium breeders.

    Meanwhile, it might behoove our political leaders to consider the question of why it was once possible to build more than 50 experimental reactors at what is now Idaho National Laboratory alone in a relatively short period of time for a small fraction of what similar reactors would cost today.  Merely negotiating the regulatory hurdles for building a power reactor based on anything as novel as the thorium fuel cycle would take the better part of a decade.  All these hurdles have been put in place in the name of “safety.”  That begs the question of how “safe” we will be if we lack reliable sources of electric energy.  There is a point beyond which excessive regulation itself becomes unsafe.

  • The Bomb and the Nuclear Posture Review

    Posted on April 22nd, 2017 Helian No comments

    A Nuclear Posture Review (NPR) is a legislatively mandated review, typically conducted every five to ten years.  It assesses such things as the role, safety and reliability of the weapons in the U.S. nuclear stockpile, the status of facilities in the nuclear weapons complex, and nuclear weapons policy in areas such as nonproliferation and arms control.  The last one was conducted in 2010.  The Trump Administration directed that another one be conducted this year, and the review is already in its initial stages.  It should be finished by the end of the year.  There is reason for concern about what the final product might look like.

    Trump has made statements to the effect that the U.S. should “expand its nuclear capability,” and that, “We have nuclear arsenals that are in very terrible shape.  They don’t even know if they work.”  Such statements have typically been qualified by his aides.  It’s hard to tell whether they reflect serious policy commitments, or just vague impressions based on a few minutes of conversation with some Pentagon wonk.  In fact, there are deep differences of opinion about these matters within the nuclear establishment.  That’s why the eventual content of the NPR might be problematic.  There have always been people within the nuclear establishment, whether at the National Nuclear Security Administration (NNSA), the agency within the Department of Energy responsible for maintaining the stockpile, or in the military, who are champing at the bit to resume nuclear testing.  Occasionally they will bluntly question the reliability of the weapons in our stockpile, even though by that very act they diminish the credibility of our nuclear deterrent.  If Trump’s comments are to be taken seriously, the next NPR may reflect the fact that they have gained the upper hand.  That would be unfortunate.

    Is it really true that the weapons in our arsenal are “in very terrible shape,” and we “don’t even know if they work?”  I doubt it.  In the first place, the law requires that both the Department of Energy and the Department of Defense sign off on an annual assessment that certifies the safety and reliability of the stockpile.  They have never failed to submit that certification.  Beyond that, the weapons in our stockpile are the final product of more than 1000 nuclear tests.  They are both safe and robust.  Any credible challenge to their safety and reliability must cite some plausible reason why they might fail.  I know of no such reason.

    For the sake of argument, let’s consider what might go wrong.  Modern weapons typically consist of a primary and a secondary.  The primary consists of a hollow “pit” of highly enriched uranium or plutonium surrounded by high explosive.  Often it is filled with a “boost” gas consisting of a mixture of deuterium and tritium, two heavy isotopes of hydrogen.  When the weapon is used, the high explosive implodes the pit, causing it to form a dense mass that is highly supercritical.  At the same time, nuclear fusion takes place in the boost gas, producing highly energetic neutrons that enhance the yield of the primary.  At the right moment an “initiator” sends a burst of neutrons into the imploded pit, setting off a chain reaction that results in a nuclear explosion.  Some of the tremendous energy released in this explosion in the form of x-rays then implodes the secondary, causing it, too, to explode, adding to the yield of the weapon.

    What could go wrong?  Of course, explosives are volatile.  Those used to implode the primary might deteriorate over time.  However, these explosives are carefully monitored to detect any such deterioration.  Other than that, the tritium in the boost gas is radioactive, and has a half life of only a little over 12 years.  It will gradually decay into helium, reducing the effectiveness of boosting.  This, too, however is a well understood process, and one which is carefully monitored and compensated for by timely replacement of the tritium.  Corrosion of key parts might occur, but this too, is carefully checked, and the potential sources are well understood.  All these potential sources of uncertainty affect the primary.  However, much of the uncertainty about their effects can be eliminated experimentally.  Of course, the experiments can’t include actual nuclear explosions, but surrogate materials can be substituted for the uranium and plutonium in the pit with similar properties.  The implosion process can then be observed using powerful x-ray or proton beams.  Unfortunately, our experimental capabilities in this area are limited.  We cannot observe the implosion process all the way from the initial explosion to the point at which maximum density is achieved in three dimensions taking “snapshots” at optimally short intervals.  To do that, we would need what has been referred to as an Advanced Hydrodynamic Facility, or AHF.

    We currently have an unmatched suite of above ground experimental facilities for studying the effects of aging on the weapons in our stockpile, including the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, the Z Machine at Sandia National Laboratories, and the Dual-Axis Radiographic Hydrodynamic Test facility (DARHT) at Los Alamos.  These give us a very significant leg up on the international competition when it comes to maintaining our stockpile.  That is a major reason why it would be foolish for us to resume nuclear testing.  We would be throwing away this advantage.  Unfortunately, while we once seriously considered building an AHF, basically an extremely powerful accelerator, we never got around to doing so.  It was a serious mistake.  If we had such a facility, it would effectively pull the rug out from under the feet of those who want to resume testing.  It would render all arguments to the effect that “we don’t even know if they work” moot.  We could demonstrate with a very high level of confidence that they will indeed work.

    But that’s water under the bridge.  We must hope that cooler heads prevail, and the NPR doesn’t turn out to be a polemic challenging the credibility of the stockpile and advising a resumption of testing.  We’re likely to find out one way or the other before the end of the year.  Keep your fingers crossed.

  • Nuclear Fusion Update

    Posted on October 17th, 2016 Helian No comments

    At the moment the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is in a class by itself when it comes to inertial confinement fusion (ICF) facilities.  That may change before too long.  A paper by a group of Chinese authors describing a novel 3-axis cylindrical hohlraum design recently appeared in the prestigious journal Nature.  In ICF jargon, a “hohlraum” is a container, typically cylindrical in form.  Powerful laser beams are aimed through two or more entrance holes to illuminate the inner wall of the hohlraum, producing a burst of x-rays.  These strike a target mounted inside the hohlraum containing fusion fuel, typically consisting of heavy isotopes of hydrogen, causing it to implode.  At maximum compression, a series of shocks driven into the target are supposed to converge in the center, heating a small “hot spot” to fusion conditions.  Unfortunately, such “indirect drive” experiments haven’t worked so far on the NIF.  The 1.8 megajoules delivered by NIF’s 192 laser beams haven’t been enough to achieve fusion with current target designs, even though the beams are very clean and uniform, and the facility itself is working as designed.  Perhaps the most interesting thing about the Chinese paper is not their novel three axis hohlraum design, but the fact that they are still interested in ICF at all in spite of the failure of the NIF to achieve ignition to date.  To the best of my knowledge, they are still planning to build SG-IV, a 1.5 megajoule facility, with ignition experiments slated for the early 2020’s.

    Why would the Chinese want to continue building a 1.5 megajoule facility in spite of the fact that U.S. scientists have failed to achieve ignition with the 1.8 megajoule NIF?  For the answer, one need only look at who paid for the NIF, and why.  The project was paid for by the people at the Department of Energy (DOE) responsible for maintaining the nuclear stockpile.  Many of our weapons designers were ambivalent about the value of achieving ignition before the facility was built, and were more interested in the facility’s ability to access physical conditions relevant to those in exploding nuclear weapons for studying key aspects of nuclear weapon physics such as equation of state (EOS) and opacity of materials under extreme conditions.  I suspect that’s why the Chinese are pressing ahead as well.  Meanwhile, the Russians have also announced a super-laser project of their own that they claim will deliver energies of 2.8 megajoules.

    Meanwhile, in the wake of the failed indirect drive experiments on the NIF, scientists in favor of the direct drive approach have been pleading their case.  In direct drive experiments the laser beams are shot directly at the fusion target instead of at the inner walls of a hohlraum.  The default approach for the NIF has always been indirect drive, but the alternative approach may be possible using an approach called “polar direct drive.”  In recent experiments at the OMEGA laser facility at the University of Rochester’s Laboratory for Laser Energetics, the nation’s premier direct drive facility, scientists claim to have achieved results that, if scaled up to energies available on the NIF would produce five times more fusion energy output than has been achieved with indirect drive to date.

    Meanwhile, construction continues on ITER, a fusion facility designed purely for energy applications.  ITER will rely on magnetic plasma confinement, the other “mainstream” approach to harnessing fusion energy.  The project is a white elephant that continues to devour ever increasing amounts of scarce scientific funding in spite of the fact that the chances that magnetic fusion will ever be a viable source of electric power are virtually nil.  That fact should be obvious by now, and yet the project staggers forward, seemingly with a life of its own.  Watching its progress is something like watching the Titanic’s progress towards the iceberg.  Within the last decade the projected cost of ITER has metastasized from the original 6 billion euros to 15 billion euros in 2010, and finally to the latest estimate of 20 billion euros.  There are no plans to even fuel the facility for full power fusion until 2035!  It boggles the mind.

    Magnetic fusion of the type envisioned for ITER will never come close to being an economically competitive source of power.  It would already be a stretch if it were merely a question of controlling an unruly plasma and figuring out a viable way to extract the fusion energy.  Unfortunately, there’s another problem.  Remember all those yarns you’ve been told about how an unlimited supply of fuel is supposed to be on hand in the form of sea water?  In fact, reactors like ITER won’t work without a heavy isotope of hydrogen known as tritium.  A tritium nucleus contains a proton and two neutrons, and, for all practical purposes, the isotope doesn’t occur in nature, in sea water or anywhere else.  It is highly radioactive, with a very short half-life of a bit over 12 years, and the only way to get it is to breed it.  We are told that fast neutrons from the fusion reactions will breed sufficient tritium in lithium blankets surrounding the reaction chamber.  That may work on paper, but breeding enough of the isotope and then somehow extracting it will be an engineering nightmare.  There is virtually no chance that such reactors will ever be economically competitive with renewable power sources combined with baseline power supplied by proven fission breeder reactor technologies.  Such reactors can consume most of the long-lived transuranic waste they produce.

    In short, ITER should be stopped dead in its tracks and abandoned.  It won’t be, because too many reputations and too much money are on the line.  It’s too bad.  Scientific projects that are far worthier of funding will go begging as a result.  At best my descendants will be able to say, “See, my grandpa told you so!”

  • 3+2: More Tinkering with the Nuclear Arsenal

    Posted on October 10th, 2016 Helian No comments

    It really seems as if the weapon designers at the nation’s three nuclear weapons laboratories, Los Alamos, Livermore, and Sandia, never really believed that nuclear testing would ever end.  If so, they were singularly blind to the consequences.  Instead of taking the approach apparently adopted by the Russians of designing and testing robust warheads that could simply be scrapped and replaced with newly manufactured ones at the end of their service life, they decided to depend on a constant process of refurbishing old warheads, eliminating the ability to make new ones in the process.  When our weapons got too old, they would be repeatedly patched up in so-called Life Extension Programs, or LEPs.  Apparently it began to occur to an increasing number of people in the weapons community that maintaining the safety and reliability of the stockpile indefinitely using that approach might be a bit problematic.

    The first “solution” to the problem proposed by the National Nuclear Security Administration (NNSA), the semi-autonomous agency within the Department of Energy (DOE) responsible for maintaining the nuclear stockpile, was the Reliable Replacement Warhead (RRW).  It was to be robust, easy to manufacture, and easy to maintain.  It was also a new, untested design.  As such, it would have violated the spirit, if not the letter, of Article VI of the Non-proliferation Treaty (NPT).  If it had been built, it would also very likely have forced violation of the Comprehensive Nuclear Test Ban Treaty (CTBT), which the U.S. has signed, but never ratified.  It was claimed that the RRW could be built and certified without testing.  This was very probably nonsense.  There have always been more or less influential voices within NNSA, the Department of Defense (DoD), and the weapons labs, in favor of a return to nuclear testing.  That would not have been a good thing then, and I doubt that it will be a good thing at any foreseeable time in the future.  In general, I think we should do our best to keep the nuclear genie bottled up as long as possible.  Fortunately, Congress agreed and killed the RRW Program.

    That didn’t stop the weaponeers.  They just tried a new gambit.  It’s called the “3+2 Strategy.”  There are currently four types of ballistic missile warheads, two bombs, and a cruise missile warhead in the U.S. arsenal.  The basic idea of 3+2 would be to reduce this to three “interoperable” ballistic missile warheads and two air delivered weapons (a bomb and a cruise missile), explaining the “3+2.”  In the process, the conventional chemical explosives that drive the implosion of the “atomic bomb” stage of the weapons would be replaced by insensitive high explosives (IHE).  The result would supposedly be a safer, more secure stockpile that would be easier to maintain.  The price tag, in round numbers, would be $60 billion.

    I can only hope Congress will be as quick to deep six 3+2 as it was with the RRW.  The 3+2 will require tinkering not only with the bits surrounding the nuclear explosive package (NEP), but with the NEP itself.  In other words, its just as much a violation of the spirit of Article VI of the NPT as was the RRW.  The predictable result of any such changes will be the “sudden realization” by the weapons labs somewhere down the line that they can’t certify the new designs without a return to nuclear testing.  There’s a better and, in the long run, probably cheaper way to maintain the stockpile.

    In the first place, we need to stop relying on LEPs, and return to manufacturing replacement weapons.  The common argument against this is that we have lost the ability to manufacture critical parts of our weapons since the end of testing, and in some cases the facilities and companies that supplied the parts no longer exist.  Nonsense!  The idea that a country responsible for a quarter of the entire world’s GDP has lost the ability to reproduce the weapons it was once able to design, build and test in a few years is ridiculous.  We are told that subtle changes in materials might somehow severely degrade the performance of remanufactured weapons.  I doubt it.  Regardless, DOE has always known there was a solution to that problem.  It’s called the Advanced Hydrodynamic Facility, or AHF.

    Basically, the AHF would be a giant accelerator facility capable of producing beams that would be able to image an imploding nuclear weapon pit in three dimensions and at several times during the implosion.  Serious studies of such a facility were done as long ago as the mid-90’s, and there is no doubt that it is feasible.  In actual experiments, of course, highly enriched uranium and plutonium would be replaced by surrogate materials such as tungsten, but they would still determine with a high degree of confidence whether a given remanufactured primary would work or not.  The primary, or “atomic bomb” part of a weapon supplies the energy that sets off the secondary, or thermonuclear part.  If the primary, of a weapon works, then there can be little doubt that the secondary will work as well.  The AHF would be expensive, which is probably the reason it still hasn’t been built.  Given the $60 billion cost of 3+2, that decision may well prove to be penny-wise and pound-foolish.

    The whole point of having a nuclear arsenal is its ability to deter enemies from attacking us.  Every time people who are supposed to be the experts about such things question the reliability of our stockpile, they detract from its ability to deter.  I think a remanufacturing capability along with the AHF is the best way to shut them up, preventing a very bad decision to resume nuclear testing in the process.  I suggest we get on with it.

  • Hillary and Her Classified E-mails

    Posted on February 14th, 2016 Helian 3 comments

    Rather than leave my readers in suspense, let me just say it up front.  If any of the “little people” working for the government, whether as feds or contractors, used a private computer for official business the way Hillary Clinton did, they would be fired.  If they used it to store and send classified information, a lot worse might happen to them.  By the letter of the law, they would certainly be punishable with heavy fines and/or jail time.  It is one of the more amusing and/or disturbing phenomena of the early 21st century, depending on your point of view, that such a person is even being seriously considered as a candidate for President of the United States.

    The latest story about the subject on Foxnews is typical of the rampant disinformation being spread on the subject in the mass media.  Under the headline, “New batch of Clinton emails released, 84 now marked ‘classified’,” it continues with the byline, “State Department release 551 documents from former Secretary of State Hillary Clinton’s email account, including 84 that are considered to be classified today, but not at the time they were initially sent.”  Is it really too much to ask that these people occasionally consult, at the very least, some new hire who’s actually taken the elementary training course in security typically required for anyone who routinely handles sensitive information?  One can never assume information is unclassified because it has not been officially declared and marked classified.  If there is any doubt on the matter, it cannot simply be blown out to the general public without a second thought.  It must be submitted to a competent authority for a decision on whether and at what level it should be protected.  Regardless of whether it is classified or otherwise sensitive or not, it is illegal to transfer official government information to a private computer.

    Let me explain how this works.  There are two major types of classified information; that which is protected by executive order, and that which is protected by statute.  Information protected by executive order is known as National Security Information, or NSI.  Each President typically releases an order early in his term with details on how such information is to be protected, for how long, etc.  The latest such order, E.O. 13526, was issued by President Obama in 2009.  Other major types of information, dealing with such things as the design and use of nuclear weapons and the production of special nuclear material such as enriched uranium and plutonium, are classified by statute, namely, the Atomic Energy Act of 1954, as amended.  The most sensitive category of this type of information is known as Restricted Data, or RD.  The Atomic Energy Act established another category of such information pertaining mainly to the military use of and yield of nuclear weapons, known as Formerly Restricted Data, or FRD.  There is also a third, seldom encountered category, dealing mainly with foreign intelligence information, known as Transclassified Foreign Nuclear Information, or TFNI.  The levels of classification, from top to bottom in order of sensitivity, are Top Secret, Secret and Confidential.  The categories, from top to bottom in order of sensitivity, are RD, FRD, TFNI, and NSI.

    Information that is protected by statute, such as RD, is “born classified.”  It is under the purview of the Department of Energy (DOE).  If there is any doubt whether it must be protected or not, it must be submitted to a “Derivative Classifier,” who consults classification guides within his/her area of competence to decide whether it is classified or not, and at what level.  If the guides don’t cover it, it may be submitted to one of the few individuals in the country with Original Classification authority for a determination.  RD is never automatically declassified, nor must a date or event be set for its eventual declassification.  RD information may occasionally be declassified by proper authority.  In that case, another specially trained individual, known as a Derivative Declassifier, is appointed to decide whether documents are no longer classified, or may be classified at a lower level.  Note the important distinction between information and documents.  In some cases declassifiers are authorized to act alone, and in others declassification decisions must be made by a declassifier and another classifier or declassifier acting together.

    NSI is not “born classified.”  However, it may not be automatically assumed unclassified, either.  Each government agency has authority over its own NSI.  Each typically has the equivalent of DOE’s Original Classifiers, Derivative Classifiers, and classification guides.  Unlike RD, a date or event must be set for declassification of NSI.  Under the current executive order, declassification must occur within 25 years, except under special circumstances.  Currently, NSI documents may not be automatically declassified, even when the declassification date has passed or the declassification event has happened.  They must first be reviewed by an authorized declassifier.

    Other than classified information, there are other types of information which must be protected, and to which legal penalties apply if released deliberately or through negligence.  These include Official Use Only, which must meet one of the nine exemptions to the Freedom of Information Act, or FOIA, Unclassified Controlled Nuclear Information, or UCNI (DOE), Safeguards Information (NRC), Protected Critical Infrastructure Information or PCII (DHS), etc.  It is illegal, and the lowliest employee of the federal government should know it’s illegal, to have any of these types of information on a private computer.

    So much for a very elementary description of the classification process in the US.  Some of the above is relevant to the case of Hillary Clinton, and some not.  However, the fact that she simply ignored all the legal and administrative requirements regarding the handling and protection of sensitive information demonstrates that she is incompetent to be a federal mailroom employee, far less President of the United States.  It is sad but hardly surprising in this day and age that most journalists and media organizations have such an abject lack of any sense of a responsibility to inform the public that they ignore all these facts.  Their main function, as far as they are concerned, is to defeat the hated and despised conservative outgroup.  As a result we find them circling the wagons around her, determined to suppress any hint of the real gravity and implications of her incompetence as Secretary of State.  This should provide us with a rather clear indication of what they are talking about when they speak of the “moral compass” referred to in my previous post.

    As my readers know, I don’t believe in the existence of objective moral truths.  However, I am human.  As a result, I experience moral emotions.  When I contemplate the fact that Hillary Clinton is very likely to become President of my country, I experience a moral emotion that is familiar to all of us.  Shame.

  • On Losing Our “Moral Compass” in Syria

    Posted on February 13th, 2016 Helian 2 comments

    It’s important to understand morality.  For example, once we finally grasp the fact that it exists solely as an artifact of evolution, it may finally occur to us that attempting to solve international conflicts in a world full of nuclear weapons by consulting moral emotions is probably a bad idea.  Syria is a case in point.  Consider, for example, an article by Nic Robertson entitled, From Sarajevo to Syria: Where is the world’s moral compass?, that recently turned up on the website of CNN.  The author suggests that we “solve” the Syrian civil war by consulting our “moral compass.”  In his opinion that is what we did in the Balkans to end the massacres in Bosnia and Kosovo.  Apparently we are to believe that the situation in Syria is so similar that all we have to do is check the needle of the “moral compass” to solve that problem as well.  I’m not so sure about that.

    In the first place, the outcomes of following a “moral compass” haven’t always been as benign as they were in Bosnia and Kosovo.  Czar Nicholas was following his “moral compass” when he rushed to the aid of Serbia in 1914, precipitating World War I.  Hitler was following his “moral compass” when he attacked Poland in 1939, bringing on World War II.  Apparently it’s very important to follow the right “moral compass,” but the author never gets around to specifying which one of the many available we are to choose.  We must assume he is referring to his own, personal “moral compass.”  He leaves us in doubt regarding its exact nature, but no doubt it has much in common with the “moral compass” of the other journalists who work for CNN.  Unlike earlier versions, we must hope that this one is proof against precipitating another world war.

    If we examine this particular “moral compass” closely, we find that it possesses some interesting idiosyncrasies.  It points to the conclusion that there is nothing wrong with using military force to depose a government recognized as legitimate by the United Nations.  According to earlier, now apparently obsolete versions of the “moral compass,” this sort of thing was referred to as naked aggression, and was considered “morally bad.”  Apparently all that has changed.  Coming to the aid of a government so threatened, as Russia is now doing in Syria, used to be considered “good.”  Under the new dispensation, it has become “bad.”  It used to be assumed that governments recognized by the international community as legitimate had the right to control their own airspaces.  Now the compass needle points to the conclusion that control over airspaces is a matter that should be decided by the journalists at CNN.  We must, perforce, assume that they have concocted a “moral compass” superior to anything ever heard of by Plato and Socrates, or any of the other philosophers who plied the trade after them.

    I suggest that, before blindly following this particular needle, we consider rationally what the potential outcomes might be.  Robertson never lays his cards on the table and tells us exactly what he has in mind.  However, we can get a pretty good idea by consulting the article.  In his words,

    Horror and outrage made the world stand up to Bosnia’s bullies after that imagination and fear had ballooned to almost insurmountable proportion.

    Today it is Russia’s President Vladimir Putin whose military stands alongside Syrian President Bashar al-Assad’s army. Together they’ve become a force no nation alone dares challenge. Their power is seemingly set in stone.

    It would seem, then, based on the analogies of Bosnia and Kosovo, where we did “good,” that Robertson is suggesting we replace the internationally recognized government of Syria by force and confront Russia, whose actions within Syria’s borders are in response to a request for aid by that government.  In the process it would be necessary for us to defeat and humiliate Russia.  It was out of fear of humiliation that Russia came to Serbia’s aid in 1914.  Are we really positive that Russia will not risk nuclear war to avoid a similar humiliation today?  It might be better to avoid pushing our luck to find out.

    What of the bright idea of replacing the current Syrian government?  It seems to me that similar “solutions” really didn’t work out too well in either Iraq or Libya.  Some would have us believe that “moderates” are available in abundance to spring forth and fill the power vacuum.  So far, I have seen no convincing evidence of the existence of these “moderates.”  Supposing they exist, I suspect the chances that they would be able to control a country brimming over with religious fanatics of all stripes without a massive U.S. military presence are vanishingly small.  In other words, I doubt the existence of a benign alternative to Bashar al-Assad.  Under the circumstances, is it really out of the question that the best way to minimize civilian casualties is not by creating a power vacuum, or by allowing the current stalemate to drag on, but by ending the civil war in exactly the way Russia is now attempting to do it; by defeating the rebels?  Is it really worth risking a nuclear war just so we can try the rather dubious alternatives?

    Other pundits (see, for example, here, here, and here) inform us that Turkey “cannot stand idly by” while Syria and her Russian ally regain control over Aleppo, a city within her own borders.  Great shades of the Crimean War!  What on earth could lead anyone to believe that Turkey is our “ally” in any way, shape or form other than within the chains of NATO?  Turkey is a de facto Islamist state.  She actively supports the Palestinians against another of our purported allies, Israel.  Remember the Palestinians?  Those were the people who danced in the streets when they saw the twin towers falling.  She reluctantly granted access to Turkish bases for U.S. airstrikes against ISIS only so she would have a free hand attacking the Kurds, one of the most consistently pro-U.S. factions in the Middle East.  She was foolhardy enough to shoot down a Russian plane in Syrian territory, killing its pilot, for the “crime” of violating her airspace for a grand total of 17 seconds.  She cynically exploits the flow of refugees to Europe as a form of “politics by other means.”  Could there possibly be any more convincing reasons for us to stop playing with fire and get out of NATO?  NATO is a ready-made fast track to World War III on behalf of “allies” like Turkey.

    But I digress.  The point is that the practice of consulting something as imaginary as a “moral compass” to formulate foreign policy is unlikely to end well.  It assumes that, after all these centuries, we have finally found the “correct” moral compass, and the equally chimerical notion that “moral truths” exist, floating about as disembodied spirits, quite independent of the subjective imaginations of the employees of CNN.  Forget about the “moral compass.”  Let us identify exactly what it is we want to accomplish, and the emotional motivation for those desires.  Then, assuming we can achieve some kind of agreement on the matter, let us apply the limited intelligence we possess to realize those desires.

    Morality exists because the behavioral predispositions responsible for it evolved, and they evolved because they happened to promote the survival of genes in times radically different than the present.  It exists for that reason alone.  It follows that, if there really were such things as “moral truths,” then nothing could possibly be more immoral than failing to survive.  We would do well to keep that consideration in mind in determining the nature of our future relationship with Russia.

  • Nuclear Update: Molten Salt, Rugby Balls, and the Advanced Hydrodynamic Facility

    Posted on August 7th, 2015 Helian No comments

    I hear at 7th or 8th hand that the folks at DOE have been seriously scratching their heads about the possibility of building a demonstration molten salt reactor.  They come in various flavors, but the “default” version is a breeder, capable of extracting far more energy from a given quantity of fuel material than current reactors by converting thorium into fissile uranium 233.  As they would have a liquid core, the possibility of a meltdown would be eliminated.  The copious production of neutrons in such reactors would make it possible to destroy the transuranic actinides, such as americium and curium, and, potentially, also some of the most long-lived radioactive products produced in fission reactions.  As a result, the residual radioactivity from running such a reactor for, say, 30 years, would potentially be less than that of the ore from which the fuel was originally extracted in under 500 years, a far cry from the millions commonly cited by anti-nuke alarmists.  Such reactors would be particularly attractive for the United States, because we have the largest proven reserves of thorium on the planet.  Disadvantages include the fact that uranium 233 is a potential bomb material, and therefore a proliferation concern, and the highly corrosive nature of the fluoride and/or chloride “salts” in the reactor core.  More detailed discussions of the advantages and disadvantages may be found here and here.

    The chances that the U.S. government will actually provide the funding necessary to build a molten salt or any other kind of advanced reactor are, unfortunately, slim and none.  We could do such things in the 50’s and 60’s with alacrity, but those days are long gone, and the country seems to have fallen victim to a form of technological palsy.  That’s too bad, because private industry won’t take up the slack.  To the extent they’re interested in nuclear at all, the profit motive rules.  At the moment, the most profitable way to generate nuclear energy is with reactors that simply burn naturally occurring uranium, wasting the lion’s share of the potential energy content, and generating copious amounts of long-lived radioactive waste for which no rational long term storage solution has yet been devised.  In theory, DOE’s national laboratories should be stepping in to take up the slack, doing the things that industry can’t or won’t do.  In reality what they do is generate massive stacks of paper studies and reports on advanced systems that have no chance of being built.  Enough must have accumulated since the last research reactor was actually built at any of the national labs to stretch back and forth to the moon several times.  Oh, well, we can take comfort in the knowledge that at least some people at DOE are thinking about the possibilities.

    Moving right along, as most of my readers are aware, the National Ignition Facility, or NIF, did not live up to its name.  It failed to achieve inertial confinement fusion (ICF) ignition in the most recent round of experiments, missing that elusive goal by nearly two orders of magnitude.  The NIF is a giant, 192 beam laser system at Lawrence Livermore National Laboratory (LLNL) that focuses all of its 1.8 megajoules of laser energy on a tiny target containing deuterium and tritium, two heavy isotopes of hydrogen.  Instead of generating energy by splitting or “fissioning” heavy atoms, the goal is to get these light elements to “fuse,” releasing massive amounts of energy.

    Actually, the beams don’t hit the target itself.  Instead they’re focused through two holes in the ends of a tiny cylinder, known as a hohlraum, that holds a “capsule” of fuel material mounted in its center.  It’s what’s known as the indirect drive approach to ICF, as opposed to direct drive, in which the beams are focused directly on a target containing the fuel material.  When the beams hit the inside walls of the cylinder they generate a burst of x-rays.  These are what actually illuminate the target, causing it to implode to extremely high densities.  At just the right moment a “hot spot” is created in the very center of this dense, imploded fuel material, where fusion ignition begins.  The fusion reactions create alpha particles, helium nuclei containing two neutrons and two protons, which then smash into the surrounding “cold” fuel material, causing it to ignite as well, resulting in a “burn wave,” which spreads outward, igniting the rest of the fuel.  For this to happen, everything has to be just right.  The most important thing is that the implosion be almost perfectly symmetric, so that the capsule isn’t squished into a “pancake,” or squashed into a “sausage,” but is very nearly spherical at the point of highest density.

    Obviously, everything wasn’t just right in the recently concluded ignition experiments.  There are many potential reasons for this.  Material blowing off the hohlraum walls could expand into the interior in unforeseen ways, intercepting some of the laser light and/or x-rays, resulting in asymmetric illumination of the capsule.  So-called laser/plasma interactions with abstruse names like stimulated Raman scattering, stimulated Brillouin scattering, and two plasmon decay, could be more significant than expected, absorbing laser light so as to prevent symmetric illumination and at the same time generating hot electrons that could potentially preheat the fuel, making it much more difficult to implode and ignite.  There are several other potential failure mechanisms, all of which are extremely difficult to model on even the most powerful computers, especially in all three dimensions.

    LLNL isn’t throwing in the towel, though.  In fact, there are several promising alternatives to indirect drive with cylindrical hohlraums.  One that recently showed promise in experiments on the much smaller OMEGA laser system at the University of Rochester’s Laboratory for Laser Energetics (LLE) is substitution of “rugby ball” shaped targets in place of the “traditional” cylinders.  According to the paper cited in the link, these “exhibit advantages over cylinders, in terms of temperature and of symmetry control of the capsule implosion.”  LLNL could also try hitting the targets with “green” laser light instead of the current “blue.”  The laser light is initially “red,” but is currently doubled and then tripled in frequency by passing it through slabs of a special crystal material, shortening its wavelength to the shorter “blue” wavelength, which is absorbed more efficiently.  However, each time the wavelength is shortened, energy is lost.  If “green” light were used, as much as 4 megajoules of energy could be focused on the target instead of the current maximum of around 1.8.  If “green” is absorbed well enough and doesn’t set off excessive laser/plasma interactions, the additional energy just might be enough to do the trick.  Other possible approaches include direct drive, hitting the fuel containing target directly with the laser beams, and “fast ignitor,” in which a separate laser beam is used to ignite a hot spot on the outside of the “cold,” imploded fuel material instead of relying on the complicated central hot spot approach.

    Regardless of whether ignition is achieved on the NIF or not, it will remain an extremely valuable experimental facility.  The reason?  Even without ignition it can generate extreme material conditions that are relevant to those that exist in exploding nuclear weapons.  As a result, it gives us a significant leg up over other nuclear weapons states in an era of no nuclear testing by enabling us to field experiments relevant to the effects of aging on the weapons in our stockpile, and suggesting ways to insure they remain safe and reliable.  Which brings us to the final topic of this post, the Advanced Hydrodynamic Facility, or AHF.

    The possibility of building such a beast was actively discussed and studied back in the 90’s, but Google it now and you’ll turn up very little.  It would behoove us to start thinking seriously about it again.  In modern nuclear weapons, conventional explosives are used to implode a “pit” of fissile material to supercritical conditions.  The implosion must be highly symmetric or the pit will “fizzle,” failing to produce enough energy to set off the thermonuclear “secondary” of the weapon that produces most of the yield.  The biggest uncertainty we face in maintaining the safety and reliability of our stockpile is the degree to which the possible deterioration of explosives, fusing systems, etc., will impair the implosion of the pit.  Basically, an AHF would be a system of massive particle accelerators capable of generating bursts of hard x-rays, or, alternatively, protons, powerful enough to image the implosion of the fission “pit” of a nuclear weapon at multiple points in time and in three dimensions.  Currently we have facilities such as the Dual-Axis Radiographic Hydrodynamic Test Facility (DARHT) at Los Alamos National Laboratory (LANL), but it only enables us study the implosion of small samples of surrogate pit material.  An AHF would be able to image the implosion of actual pits, with physically similar surrogate materials replacing the fissile material.

    Obviously, such experiments could not be conducted in a conventional laboratory.  Ideally, the facility would be built at a place like the Nevada Test Site (NTS) north of Las Vegas.  Experiments would be fielded underground in the same way that actual nuclear tests were once conducted there.  That would have the advantage of keeping us prepared to conduct actual nuclear tests within a reasonably short time if we should ever be forced to do so, for example, by the resumption of testing by other nuclear powers.  With an AHF we could be virtually certain that the pits of the weapons in our arsenal will work for an indefinite time into the future.  If the pit works, we will also be virtually certain that the secondary will work as well, and the reliability of the weapons in our stockpile will be assured.

    Isn’t the AHF just a weaponeer’s wet dream?  Why is it really necessary?  Mainly because it would remove once and for all any credible argument for the resumption of nuclear testing.  Resumption of testing would certainly increase the nuclear danger to mankind, and, IMHO, is to be avoided at all costs.  Not everyone in the military and weapons communities agrees.  Some are champing at the bit for a resumption of testing.  They argue that our stockpile cannot be a reliable deterrent if we are not even sure if our weapons will still work.  With an AHF, we can be sure.  It’s high time for us to dust off those old studies and give some serious thought to building it.

    ICF

  • Do We Really Need New Nukes?

    Posted on December 2nd, 2014 Helian No comments

    If an article that just appeared in the LA Times is any indication, the agitation for jump-starting the nuclear weapons program at the Department of Energy (DOE) and the three nuclear weapons laboratories (Lawrence Livermore, Los Alamos, and Sandia National Laboratories) continues unabated. Entitled “New nuclear weapons needed, many experts say, pointing to aged arsenal,” it cites all the usual talking points of the weaponeers. For example,

    Warheads in the nation’s stockpile are an average of 27 years old, which raises serious concerns about their reliability, they say. Provocative nuclear threats by Russian President Vladimir Putin have added to the pressure to not only design new weapons but conduct underground tests for the first time since 1992.

    “It seems like common sense to me if you’re trying to keep an aging machine alive that’s well past its design life, then you’re treading on thin ice,” said Rep. Mac Thornberry (R-Texas), chairman-elect of the House Armed Services Committee. “Not to mention, we’re spending more and more to keep these things going.”

    Thornbury also offered support for renewed testing, saying, “You don’t know how a car performs unless you turn the key over. Why would we accept anything less from a weapon that provides the foundation for which all our national security is based on?”

    Such comments are entirely typical. They would make a lot of sense if the U.S. nuclear weapons program existed in a vacuum. However, it doesn’t. It exists in a world with several other major nuclear powers, and they all have the same problems. Under the circumstances, the fact that such problems exist and are shared by all the nuclear powers is less significant than the question of which nuclear power is best equipped to deal with them. The question of who will benefit by the building of new weapons and a resumption of nuclear testing depends on the answer to that question. If one country has a significant advantage over its rivals in dealing with a common problem as long as the status quo is maintained, then it would be very ill-advised to initiate a change to the status quo that would allow them to catch up.  At the moment, the United States is the country with an advantage. As noted in the article,

    The U.S. has by far the greatest archive of test data, having conducted 1,032 nuclear tests. Russia conducted 715 and China only 45.

    Beyond that, we have the ability to conduct tests with conventional explosives that mimic what goes on in the initial stages of a nuclear explosion, and superb diagnostics to extract a maximum of data from those tests. Perhaps more importantly, we have an unrivaled above ground experimental, or AGEX, capability. I refer to machines like Z at Sandia National Laboratories, or the NIF at Livermore, which are far more capable and powerful than similar facilities anywhere else in the world. Those who say they can’t access physical conditions relevant to those that occur in exploding nuclear weapons, or that they are useless for weapon effects or weapon physics experiments, either don’t know what they’re talking about or are attempting to deceive.

    As far as the NIF is concerned, it is quite true that it has so far failed to achieve its fusion ignition milestone, but that by no means rules out the possibility that it ever will. More importantly, the NIF will remain a highly useful AGEX facility whether it achieves ignition or not. Indeed, before it was built, many of the weapons designers showed little interest in ignition. It would merely “muddy the waters,” making it more difficult for the diagnostics to precisely record the results of an experiment. The NIF could access weapons-relevant conditions without it. In fact, in spite of its failure to achieve ignition to date, the NIF has been a spectacular success as far as achieving its specifications are concerned. It is more than an order of magnitude more powerful than any previously existing laser system, its 192 laser beams are highly accurate, and its diagnostic suite is superb.

    Another problem with the resumption of testing is that it will lead to the development of weapons that are much more likely to be used. Once the nuclear genie is out of the bottle, it will likely prove very difficult to put it back in. For example, again quoting the article,

    John S. Foster Jr., former director of Lawrence Livermore National Laboratory and chief of Pentagon research during the Cold War, said the labs should design, develop and build prototype weapons that may be needed by the military in the future, including a very low-yield nuclear weapon that could be used with precision delivery systems, an electromagnetic pulse weapon that could destroy an enemy’s communications systems and a penetrating weapon to destroy deeply buried targets.

    The commonly heard narrative at DOE goes something like this: “We need to develop small, precise, penetrating nuclear weapons because they will be a much better deterrent than the existing ones. Potential enemies are unlikely to believe that we would ever use one of the high yield weapons that are all that remain in the current arsenal. They would be far more likely to believe that we might use a small bunker buster that would minimize the possibility of significant collateral damage.” The problem with that narrative is that it’s true. We would be far more likely to use such a weapon than the ones in the current arsenal, and there would be no lack of voices within DOE and DoD calling for its use if an appropriate opportunity ever arose.

    I can understand the agitation for a resumption of testing. It’s a lot sexier to make things that go boom than to serve as custodians for an aging pile of existing nukes. Unfortunately, the latter course is the wiser one. By resuming nuclear testing we would really be unilaterally surrendering a huge advantage, playing into the hands of our enemies and destabilizing the nuclear landscape at the same time.