Subcritical Thorium Reactors: Dr. Rubbia’s Really Bad Idea

The Telegraph (hattip Insty) turned the hype level to max in a recent article about the potential of thorium reactors.  According to the headline, “Obama could kill fossil fuels overnight with a nuclear dash for thorium.”  Against all odds, this is to happen in three to five years with a “new Manhattan Project,” and a “silver bullet” in the form of a new generation of thorium reactors.  The author is so vague about the technologies he’s describing that it’s hard to avoid the conclusion that he simply doesn’t know what he’s talking about, and couldn’t be bothered to spend a few minutes with Google to find out.  I’ll try to translate.

It’s claimed that thorium “eats its own waste.”  In fact, thorium is very promising as a future source of energy, but this is nonsense.  Apparently it’s based on the fact that certain types of thorium reactors actually could burn their own fuel material, as well as plutonium scavenged from conventional reactor waste and other transuranics, much more completely than alternative designs.  This is certainly an advantage, but the fission products (lighter elements left over from the splitting of uranium and plutonium) would still be highly radioactive, and would certainly qualify as waste.  Such claims are so obviously spurious that they play into the hands of opponents of nuclear power.

It is also claimed that “all (thorium) is potentially usable as fuel, compared to just 0.7% for uranium.”  In fact, thorium is not a fissile material, meaning that, unlike uranium 235 (U235), which is the 0.7% of natural uranium the author is referring to, it cannot sustain a nuclear chain reaction on its own.  It must first be converted to a lighter isotope of uranium, U233, which is fissile.  In fact, the U238 that makes up most of the rest of the leftover 99.3% percent of natural uranium is “potentially usable as fuel” in that sense as well, by conversion to plutonium 239, also a fissile material.

The author is vague about exactly what kind of reactors he is referring to, lumping Dr. Carlo Rubbia’s subcritical design, which depends on a proton accelerator to provide enough neutrons to keep the fission process going, and molten fluoride salt reactors, which do not necessarily require such an accelerator.  He claims that, “Thorium-fluoride reactors can operate at atmospheric temperature,” which they certainly could not if the goal were to generate electric power.  I suspect that what he means here is that, unlike plutonium breeders, which require a high energy neutron spectrum to produce more fuel than they consume, thorium breeders could potentially use “thermal” neutrons that have been slowed to the point that their average energy, when converted to a “temperature,” would be much closer to that of the other material in the reactor core. 

In any case, the design he seems to be so excited about is Dr. Rubbia’s “energy amplifier,” which, as noted above, would be subcritical, requiring a powerful, high current proton accelerator to keep the fission process going.  It would do this via spallation, a process in which a copious source of the neutrons required to keep the reaction going would be provided via interaction of the protons with heavy nuclei such as lead, or thorium itself.  This is the process used to produce neutrons at the Oak Ridge Spallation Neutron Source.  Such reactors could easily be “turned off” by simply shutting down the source of neutrons.  However, the idea that they would be inherently “safer” is dangerously inaccurate.  In fact, they would be an ideal path to covert acquisition of nuclear weapons.  Thorium reactors work by transmuting thorium into U233, which is the isotope that fissions to produce the lion’s share of the energy.  It is also an isotope that, like U235 and Pu239, can be used to make nuclear bombs. 

The article downplays this risk as follows:

After the Manhattan Project, US physicists in the late 1940s were tempted by thorium for use in civil reactors. It has a higher neutron yield per neutron absorbed. It does not require isotope separation, a big cost saving. But by then America needed the plutonium residue from uranium to build bombs.

“They were really going after the weapons,” said Professor Egil Lillestol, a world authority on the thorium fuel-cycle at CERN. “It is almost impossible make nuclear weapons out of thorium because it is too difficult to handle. It wouldn’t be worth trying.” It emits too many high (energy) gamma rays.

What Lillestol is referring to is the fact that, in addition to U233, thorium reactors also produce a certain amount of U232, a highly radioactive isotope of uranium with a half life of 68.9 years whose decay does, indeed, release potentially deadly gamma rays.  It would be extremely difficult, if not impossible, to remove it from the U233, and, if enough of it were present, it would certainly complicate the task of building a bomb.  The key phrase here is “if enough of it were present.”  Thorium enthusiasts like Lillestol never seem to do the math.  In fact, as can be seen here, even conventional thorium breeders could be designed to produce U233 sufficiently free of U232 to allow workers to fabricate a weapon without serious danger of receiving a lethal dose of gamma rays.  However, large concentrations of highly radioactive fission products would make it very difficult to surreptitiously extract the uranium, and it would also be possible to mix the fuel material with natural or depleted uranium, reducing the isotopic concentration of U233 below that necessary to make a bomb.

With subcritical reactors of the type proposed by Rubbia, the problem of making a bomb gets a whole lot easier.  Rogue state actors, and even terrorists groups if we “succeed” in coming up with a sufficiently inexpensive design for high energy proton accelerators, could easily modify them to produce virtually pure U233, operating small facilities that it would be next to impossible for international monitors to detect.  There are two possible pathways for the production of U232 from thorium, both of which involve a reaction in which a neutron knocks two neutrons out of a heavy nucleus of Th232 or U233.  Those reactions can’t occur unless the initial neutron is carrying a lot of energy as can be seen in figure 8 of the article linked above, the threshold is around 6 million electron volts (MeV).  That means that, in order to produce virtually pure U233, all that’s necessary is to slow the incoming spallation neutrons below that energy.  That’s easily done.  Imagine two billiard balls on a table.  If you hit one as hard as you can at the other one, what happens when they collide?  If your aim was true, the first ball stops, transferring all its energy to the second one.  The same thing can be done with neutrons.  Pass the source neutrons through a layer of material full of light atoms such as paraffin or heavy water, and they will bounce off the light nuclei, losing energy in the process, until they eventually become “thermalized,” with virtually none of them having energies above 6 MeV.  If such low energy neutrons were then passed on to a subcritical core, they would produce U233 with almost no U232 contamination. 

It gets worse.  Unlike Pu239, U233 does not emit a lot of spontaneous neutrons.  That means it can be used to make a simple gun-type nuclear weapon with little fear that a stray neutron will cause it to fizzle before optimum criticality is reached.  And, by the way, a lot less of it would be needed than would be required for a similar weapon using U235, the fissile material in the bomb that destroyed Hiroshima. 

We’re quite capable of blowing ourselves up without Rubbia’s subcritical reactors.  Let’s not make it any easier than it already is.  Thorium reactors have many potential advantages over other potential sources of energy, including wind and solar.  However, if we’re going to do thorium, let’s do it right.

Contaminated Food…

First eggs, and now meat. I have a suggestion; could I and some of the other more reckless and foolhardy members of society be given access to irradiated foods? Far be it for me to suggest that everyone’s food be irradiated. The self-appointed protectors of society would pour out of the woodwork with mounds of studies “proving” the harmful effect of irradiation, more or less the same way they “proved” that childhood vaccines cause autism. Just access. That’s all I ask. Where’s the harm? If I kill myself by eating those terrible irradiated foods, young taxpayers will have one less mouth to feed.

Cold Fusion and ARPA-E

According to it’s mission statement, the Advanced Research Project Agency – Energy (ARPA-E) is supposed to have more or less the same role within the Department of Energy as DARPA has for the Department of Defense. Quoting from the statement:

ARPA-E focuses exclusively on high risk, high payoff concepts – technologies promising genuine transformation in the ways we generate, store and utilize energy.

A statement of objectives on the ARPA-E website elaborates on this theme:

To focus on creative “out-of-the-box” transformational energy research that industry by itself cannot or will not support due to its high risk but where success would provide dramatic benefits for the nation.

Apparently the source selection guys who picked the first round of 37 projects to be funded by the new office never got the word. Read over the list, and you’ll find they have a distinctly incremental, chewed over flavor.   There are projects to train bacteria to produce biofuels, projects to make better batteries, projects to do a better job of removing CO2 from flue gas, etc.  All very interesting, but the chances that any of this stuff will be “transformational” are vanishingly small.  One project area that really is “high risk, high payoff” and potentially transformational is remarkable by its absence – cold fusion.

They’re taking a very dim view of the situation at the website of Cold Fusion Times. Their take:

Corrupt individuals within the US Patent Office and elsewhere continue to cover up cold fusion applications and other alternative energy inventions. ARPA-E and the DOE tricked scores of cold fusioneers to waste their time on proposals that went into the waste basket. For what reason? It is unethical that this has continued from the crash of the Exxon Valdez through the present disaster in the Gulf of Mexico. People around the world now believe that those involved in this coverup festering since 1989 should finally be held accountable.

I can understand the frustration, but that sort of hyperbole is both counterproductive and wrong.  I have seen no evidence that any of the individuals involved in the selection process are corrupt, or that there has been a “cover up.”  Orthodox energy scientists and bureaucrats would have nothing to “cover up,” because they simply don’t believe in cold fusion.  There was no attempt to “trick” anyone.

What we are really seeing at ARPA-E is hidebound conservatism, ignorance of what has been going on in the cold fusion community, and the time-honored reticence of bureaucrats in all ages to stick their necks out and risk ridicule by supporting anything unconventional.  I wouldn’t describe ARPA-E’s failure to fund a single one of the many cold fusion proposals it received, and its singularly bland choice of awards, as “corrupt” or ”trickery.”  A more appropriate adjective that comes to mind might be “pathetic.”  These people have utterly and completely failed to grasp exactly what it is their organization is supposed to be doing. 

“High risk, high payoff?”  Get real!  Let’s hope they do better next time.

2009 Colloquium on Lattice-Assisted Nuclear Reactions (LANR) at MIT

Canadian Thistle…

…attracts butterflies (and goldfinches after it goes to seed).

Global Warming Update

It was the best of times. It was the worst of times.

The Death of the Global Warming Movement?

Shikha Dalmia thinks so. The issue has been politicized to the point that the zealots on both sides have conflated science with ideology. They speak as if the question of whether significant global warming will happen (or not) depends on who wins the ideological debate. In the end, of course, the earth will warm (or not) regardless of who makes the best speeches. The probability, and the evidence, that it will are not insignificant. Under the circumstances it seems foolhardy to continue the uncontrolled dumping of greenhouse gases into the atmosphere.

“Stealth” Fusion Progress

It didn’t take us long to master the destructive force of fusion, but taming it for more constructive applications, such as electricity production, has been harder than anyone imagined back in the day when a popular slogan was “online by ‘79.” Right, maybe in 2079 with any luck. We know of two scientifically feasible ways to get more energy out of fusion than it’s necessary to put in to ignite the fuel materials; magnetic fusion, as in ITER, or inertial confinement fusion (ICF) as at the National Ignition Facility (NIF). The problem with both approaches is not the science, but the engineering challenge of building reactors capable of generating electricity anywhere near as cheaply as the alternatives. At the moment, the chances that we will be able to do so any time in the foreseeable future seem remote.

If anyone around today lives to see the dawn of the era of fusion energy, it will probably be because some exceptionally clever researcher has hoodwinked Mother Nature and discovered how to finesse his way past the Coulomb barrier that usually keeps atomic nuclei too far apart to come within the range of the fusion-enabling strong force. Several promising candidates are already in the field, and one of them, Tri-Alpha Energy, has apparently managed to attract $50 million in private research funding. The company hasn’t revealed the nature of its approach, but it is apparently inspired by the work of Prof. Norman Rostoker of UC Irvine. One can get a broad hint from this paper co-authored by Rostoker and Tri-Alpha entitled, “Colliding Beam Fusion Reactors.” Rostoker is an emeritus professor who has been publishing papers since the 50’s, some co-authored with fusion superstars such as Nicholas Krall and Marshall Rosenbluth. Octogenarian physicists don’t often pull off such miracles, but you never know.

If he or someone else ever does manage to pull the fusion rabbit out of the hat, it would potentially put an end to our worries about energy for a very long time. It could also enable pure fusion weapons. Let’s keep our fingers crossed that it doesn’t.

Fusion Reaction

The Great Disappearing Oil Trick

Oil spills that fit the narrative never go away. Oil spills that don’t fit the narrative just disappear!

ITER: Throwing Good Money after Bad

According to the journal Nature, European nations hope to redirect more than €1 billion (US$1.25 billion) earmarked for research grants to make up a budget shortfall at the experimental ITER fusion reactor.  In an article that appeared in the July 7 issue, the editors note,

The proposal has alarmed scientists, who say that it will rob researchers of vital funds at a time when governments are planning to scale back domestic research budgets in response to the global economic downturn.

This is surely an understatement.  If I were a European scientist, I would be screaming bloody murder.  Like the International Space Station, ITER is a white elephant whose potential benefits will never come close to justifying the cost of building it.  It’s projected cost has tripled since it was estimated in 2001.  The fond hopes of the aging scientists who have devoted their careers to the pursuit of magnetic fusion energy will not be realized.  Like the International Space Station, ITER’s real effect will be to serve as a huge financial vacuum cleaner, soaking up billions in research money that could be much better spent elsewhere, including in the field of fusion energy research itself.

The problem with magnetic fusion, at least in the form represented by ITER, is that, while it is scientifically feasible, it will never be able to compete with alternative methods of producing electric power in terms of cost.  There are certainly hundreds of reactor design studies out there that claim the opposite, but, as the future will demonstrate if ITER is ever built, they are all wrong.  Among other things, the cost of a tritium economy has been grossly underestimated.  Tritium is a heavy form of hydrogen whose nucleus contains two neutrons in addition to the usual single proton.  Mixed with deuterium, another heavy isotope of hydrogen with a single extra neutron, it will be an essential fuel material in reactors such as ITER.  Deuterium occurs naturally, and is relatively common.  In other than trace amounts, tritium does not.  It must be produced artificially.  In order to produce the quantities necessary to keep a reactor like ITER running indefinitely, it will be necessary to surround the burning plasma with a thick layer of lithium.  Fast neutrons produced by fusion in the burning plasma can then produce the necessary tritium in nuclear reactions with this material. 

However, there is a slight problem.  Tritium is highly radioactive, with a half-life, the time it takes for half of any given quantity to undergo nuclear decay, of something over 12 years.  In spite of the fact that hydrogen is a notoriously slippery substance, passing with ease right through some types of metal, it will be necessary to control and contain kilograms of this material in a working magnetic fusion reactor.  In addition to its intrinsic radioactive hazard, tritium must also be carefully guarded to keep it from falling into the wrong hands.  For example, if terrorists were able to secure enough special nuclear material to build a nuclear bomb, they could potentially greatly increase its explosive yield by using tritium in the process known as boosting.  All this, not to mention the legal challenges that NIMBY’s are sure to mount to avoid living next to such an objectionable material, is unlikely to be cheap.

This and other potential show stoppers will insure that magnetic fusion reactors like ITER will never be able to compete economically.  Don’t believe me?  Wait and see.  It would be much better to use the increasingly scarce research dollars now being used to fund this particular white elephant on smaller projects, including fusion research projects, where it could do some real good.  Who knows.  They might even result in the discovery of a way to finesse Mother Nature after all and build fusion reactors that don’t need tritium and are economically competitive.

ITER

Tony Hayward sans Sackcloth and Ashes

The media in the U.S. have been making a big fuss about a sighting of BP CEO Tony Hayward at a yacht race. Apparently he’s supposed to be walking around in a circle hitting himself on the forehead with a board like the monks in Monty Python’s “Life of Brian.” I don’t blame him. He seemed to take the self-righteous hazing he endured at the hands of our grandstanding politicians with a good grace. Rep. Joe Barton, who apparently hasn’t learned that it’s a breach of protocall to refer to McCarthyism by its proper name if it’s for a good cause, actually dared to apologize for the public flogging. However, he quickly got back into line after a judicious jerk on his choke chain. As for Hayward, it seems to me that watching a yacht race is not really a mortal sin. He deserves a break, and hitting himself on the forehead with a board probably won’t significantly slow the flow of oil into the Gulf.