Nuclear Con-Fusion

At Consumer Energy Report, Andrew Holland writes Why Nuclear Fusion is Worthy of Further Research and Government Investment, which is yet another article about the promise of nuclear fusion. He makes a good summation of what we have been told about fusion since the 1950s:

Fusion is a technology that holds great promise in meeting our energy needs. By fusing together two hydrogen isotopes – deuterium and tritium – enormous amounts of energy can be produced, as predicted by Einstein’s equation, E=MC2. The heat from this reaction creates steam to spin a generator just like any other electricity power plant. Since deuterium comes from ocean water, and tritium can be bred from lithium, fusion holds the promise of providing a nearly inexhaustible supply of energy, with no pollutants, no greenhouse gases, and no radioactive waste. There is no threat of a nuclear meltdown like there is with the nuclear fission reactors of today.

This is the same process that powers the sun, and it could completely revolutionize the energy system when commercialized. However, the problem is that it is fiendishly hard to initiate a reaction anywhere other than under the tremendous gravitational force of a star. Scientists have not been able to confine the heated plasma on earth in such a way that it creates a reaction that generates more power than it put in – a term called “ignition” or “energy gain.”

Mr Holland has returned from a conference where everyone requires a lot more funding.

Critics of fusion often say that it is the energy of the future and always will be. However … there have been plans for new machines that could lead to breakthroughs, but persistent budget cuts have prevented new advances.

Even so, scientists at the conference seemed convinced that they are on a pathway to achieving ignition with energy gain over the next decade or two. These predictions are dependent upon the level of government funding – not an easy or guaranteed thing at this time – and some scientific breakthroughs. The ITER project in Cadarache, France promises to achieve energy gain when it is operational by the end of this decade.

Now, with all respect to Mr Holland, reading this opus (couldn’t resist) didn’t change my opinion in the slightest. In January 2012 Tom Murphy dealt with the problems of Nuclear Fusion and concluded that after sixty years, fusion was “the definition of hard.” I wrote Hot and Cold Running Fusion back in March 2012, and quoted Ugo Bardi:

Now, of course, it is impossible to say that tokamaks will never produce useful energy. But look at the figure at the beginning of this post. Doesn’t it make you wonder? It looks like we are just making the same machine bigger and bigger, in the hope that, eventually, it will work.

I did find something new while scanning the comments. I expected that someone would suggest LENR/cold fusion instead (which happened), that someone would suggest solar energy instead (which happened), and that someone would insist that hot fusion would never amount to anything (which also happened). I didn’t expect that anyone would still endorse the very old Project Plowshares idea of exploding hydrogen bombs in underground chambers, an extension of which is the also very old PACER concept. What was new was that Maury Markowitz cited fears of fusion radioactivity in his provocative article, Why fusion will never happen:

… boy do we need fusion! It’s unlimited, safe, clean, and cheap. It’s the perfect source of power. Except it’s not, well, any of those things.

Markowitz claims that deuterium and thorium are expensive to obtain, and that tritium doesn’t last very long. Markowitz claims that fusion reactors will create a lot of radioactive waste, which I’ve never heard mentioned before. Markowitz claims that if the liquid lithium barrier should ever catch fire, the tritium could burn with oxygen, evaporate and fall as radioactive rain. In footnotes, Markowitz cites The Trouble With Fusion, an 1983 article by MIT Prof Lawrence Lidsky, who then switched from fusion research to fission research. From a 2002 obituary:

“Larry Lidsky was one of the smartest people I ever met,” said Professor Jeffrey P. Freidberg, head of the MIT Department of Nuclear Engineering. “He was often way ahead of his time in delivering insightful and crucial analysis of the prospects of both fusion and fission power. In the fusion area, Professor Lidsky was one of the earliest engineers to point out some of the very, very difficult engineering challenges facing the program and how these challenges would affect the ultimate desirability of fusion energy. As one might imagine, his messages were not always warmly received initially, but they have nevertheless stood the test of time.”

So what did Lidsky say? A PDF of the Trouble With Fusion is available, and Lidsky essentially makes a case for yet-to-be-designed, neutron-free fission reactors instead of large fusion reactors emitting heavy neutrons:

The most serious difficulty concerns the very high energy neutrons released in the deuterium-tritium (D-T) reaction. These uncharged nuclear particles damage the reactor structure and make it radioactive. A chain of undesirable effects ensures that any reactor employing D-T fusion will be a large, complex, expensive, and unreliable source of power. That is hardly preferable to present-day fission reactors, much less the improved fission reactors that are almost sure to come.

Lidsky notes the challenges in obtaining fuel and in working with lithium, but seems to dismiss one of Markowitz’s concerns, noting that tritium is only weakly radioactive and does not linger in the body. Lidsky does, however, note that there will be so much radioactivity inside a fusion reactor that maintenance workers will not be able to service it. Repairs would have to be carried out by robots (who after stealing our jobs will conquer the world).

Lidsky was hardly the only one to criticize fusion, there have been many criticisms and many rebuttals back and forth, but the issues usually seem to boil down to complexity and cost. MSM articles on fusion, though, rarely mention radioactivity at all, implying that fusion reactors are actually much cleaner and safer than the fission reactors that have failed often enough to engender widespread opposition.

Advertisements

Tags: , , ,

3 responses to “Nuclear Con-Fusion”

  1. Maury Markowitz says :

    Just got a pingback, so…

    “Project Plowshares idea of exploding hydrogen bombs in underground chambers, an extension of the PACER”

    Yeah, who ever thought someone would be bringing that one back from the dead? I’ve recently updated the PACER article on the Wikipedia, significantly, so you might want to head over there to see the reasoning against this. Among the obvious problems with lots of bombs, etc., there is also the prediction that it would cost ten times as much as a fission reactor. So, as in my article, what’s the point?

    “yet-to-be-designed, neutron-free fission reactors instead of large fusion reactors emitting heavy neutrons”

    Indeed… in fact, many of the articles complaining about fusion research are written by other researchers who are actually arguing for their own version to be funded. That was the case here, as well as other examples like Hirsch and Forward.

    The problem is that each of these has a different design that they’re pushing, and their arguments often apply against the other alternate designs. So if you take the union of all the arguments, apparently no system could work!

    It is also worth mentioning that this particular solution, aneutronic fusion, is even more difficult than existing approaches, but orders of magnitude. People in the “mainstream” approach quickly point out several of these problems if you ask them, and some of them essentially sound insurmountable.

    “Markowitz claims that fusion reactors will create a lot of radioactive waste, which I’ve never heard mentioned before”

    This requires some explanation, and perhaps I should have spent more time on this.

    In a fission reaction, 211 MeV of energy are released. Of this, only 4.8 MeV is in neutrons. So only about 2% of that is in neutrons.

    In comparison, a D-T fusion reaction releases 17.6 MeV, of which 14.1 MeV is in the neutron, representing over 80% of the reaction energy.

    So what that means is that for a reactor to generate any given amount of real-world power, say 1 GWe, a fission reactor will be releasing 40 times less neutrons.

    So far so good?

    So what happens to those neutrons? In a fission reaction, the majority of them end up back in the fuel. Some of those keep the chain reaction going, while a few escape. In the case of a fusion reactor, practically none end up in the fuel and the vast majority escape. If everything goes right we’ll try to capture most of these in the lithium, but to get there they’ll have to go through the vacuum wall.

    Any escaped neutrons that impact with the metal cause mechanical damage to it, and can induce radioactivity. This is why reactors have limited lifespans, on the order of a decade or so. When that happens the old metal is taken out and buried.

    Now in theory the problem in the fusion case, neutron for neutron, isn’t any worse than the fission example. But the problem is the relative numbers. To make that 1 GWe fusion reactor, we’re going to be releasing HUGE numbers of neutrons – like every one the world has seen in the last decade, per day. So what happens is that the reactor breaks down very quickly and has to be replaced, and that metal is buried.

    That’s not to say that the stuff is seriously dangerous, like spent fission fuel, but any sort of practical reactor design would be creating enourmous amounts of this stuff. And that’s why all of these critics are pushing for aneutronic fusion. This avoids this problem, but only at the cost of being potentially impossible.

    Like

  2. Robert Steinhaus says :

    It would make a difference to introduce practical commercial versions fusion technology 50 years earlier than now appears feasible. Fully 2 billion people today are without access to electricity, and a clean practical version of fusion that requires no science and technology breakthroughs to build could be important to uplift the lives of billions while helping mankind to practically solve our planetary climate problems.

    PACER Fusion … [Remainder deleted. You are promoting PACER all over the net, but exploding underground nuclear bombs seems like a far worse incarnation of mountaintop removal, hydraulic fracturing and mining tar sands.]

    Like

%d bloggers like this: