A Closer Eye on Laser Fusion
In August of this year, at the Lawrence Livermore National Laboratory (LLNL) in California, a laser-based fusion experiment saw an 8x jump in fusion output compared to all previous tests.?While this work is exceptionally difficult and the progress is commendable, much of the tech media coverage of this result has conflated two different streams of fusion research. This article is part of a series of articles that I have called the Fusion Energy Oscars. In this article it will be emphasized that “fusion” research does not necessarily mean energy research.
Sword or Plowshare?
The interesting fusion result came from the National Ignition Facility (NIF). NIF was conceived of, built, and operates today for one main purpose: ‘Stockpile Stewardship’ of the American nuclear weapons arsenal.?Funding and administration of NIF is provided by National Nuclear Security Administration (NNSA). The word “ignition” here refers to a self-sustaining fusion reaction within tiny pellets of compressed fuel. Intense laser beams compress fusion fuel to the extremely high energy density states that occur when nuclear weapons detonate. NIF’s primary objective is to regularly produce this ignited state so that it can be better studied. Physics models resulting from this study will be used to manage the present and future stockpile of nuclear weapons.
Big Shot
The result obtained in a single shot this summer is certainly encouraging news for NIF which has not had an easy time approaching its nominal goal. NIF was approved and construction began in 1997, one year after the USA signed the Comprehensive Test Ban Treaty (CTBT). This treaty put an end to underground nuclear testing (atmospheric nuclear tests were banned in 1963).?Victor Reis, assistant secretary for Defense Programs within DOE and the chief architect of the Stockpile Stewardship Program said at the time:
"NIF was designed to produce, for the first time in a laboratory setting, conditions of temperature and density of matter close to those that occur in the detonation of nuclear weapons… without underground nuclear testing."
I have argued in previous posts and articles that plasma physics is hard.?NIF is certainly another case in point. A 1997 National Academy of Sciences review of NIF’s design defined ignition as fusion yield equal to or more than the laser energy input.?For years, NIF results have fallen far short of this criterion. In this summer’s record-breaking shot, 1.9 MJ of laser energy hit the target, and 1.3 MJ of fusion energy was released. Twenty-four (24) years and 6 billion dollars later the National Ignition Facility is on the threshold of ignition!?
And There Was Much Rejoicing
Those in charge of the lab are duly proud of their hard-won progress. LLNL Director Kim Budil said that this summer’s result:
“…opens the door to exciting new NIF applications to support stockpile stewardship, enables us to study robustly burning plasmas for the first time since underground testing ended"
The official LLNR press release stated that, pending peer review, the result represented ‘a significant step toward ignition’. It also included a quote from Jill Hruby, DOE under secretary for Nuclear Security and NNSA administrator:
“These extraordinary results from NIF advance the science that NNSA depends on to modernize our nuclear weapons and production as well as open new avenues of research,”
All fine and good. So where is the popular press picking up the fusion energy angle from??
Say What?...
Interestingly, the Physics Today story on the press release included a slightly longer quote from Hruby:
“These extraordinary results from NIF advance the science that NNSA depends on to modernize our nuclear weapons and production. It also offers potential new avenues of research into alternative energy sources that could aid economic development and help fight climate change,”
Perhaps this last comment, omitted in the official press release by the national lab, is the origin of the baffling emphasis on fusion energy in the press coverage of this latest NIF result. For some reason the popular press immediately conflates the work at NIF with fusion energy research. While we all want good news regarding the battle against climate change…there should be a better effort to keep the news grounded in fact.
Once Upon a Time In The West
There used to be a laser-based fusion energy project at Lawrence Livermore Labs. In the heady early days of NIF, a fusion energy project called Laser Inertial Fusion Energy (LIFE) was proposed as a prototype laser fusion power plant. The goal was to blast up to 17 fuel pellets per second, generate heat with the fusion neutrons produced, and use that heat to power a conventional electric turbine.?But of course, one would need to demonstrate net energy gain for such a scheme to work.?
Keep Your Eye on the Denominator!
Long before net gain, you need to at least break even…and for that to happen the National Ignition Facility had to produce…Ignition. But by the end of 2012, NIF was under great pressure for its failure to Ignite. NIF needed good news. In 2013 a memo by NIF associate director Dr. Ed Moses heralded a NIF test result claiming "scientific breakeven" had been finally achieved, pointing out that the fusion energy released was more than the "energy absorbed by the fuel". This announcement initially received significant fanfare in the press as it implied to many that the key objective had been achieved. What Dr. Moses neglected to emphasize was that was he had introduced a new definition of breakeven.?Since in fact ignition on NIF was far off, LIFE was cancelled in 2013.?Robert McCrory, director of the Laboratory for Laser Energetics, stated:
"In my opinion, the overpromising and overselling of LIFE did a disservice to Lawrence Livermore Laboratory."??
Others would agree. These excellent videos express how this type of con-fusion can be importantly misleading to the public.
Déjà vu all over again?
So here we are in 2021, and NIF still is yet to break even. But apparently the old swapping-out-the-denominator-in-the-energy-ratio trick is alive and well.?In this APS article we again see a scientist at NIF being creative with the definition of ignition and break even.?While it is perfectly legal to define ‘ignition’ anyway one chooses, it is also perfectly confusing. The article’s author seems to have missed the switch, claiming incorrectly that the 2021 test released, "for the first time", more energy than the fuel capsule absorbed. No. Dr. Moses correctly made that correct, yet misleading claim 8 years ago.?
Runaway Chain Reaction of…Bravado?
This oversight may seem small or semantic. But the article goes on to claim that the NIF result “takes commercial fusion-energy reactors a step closer to reality”. Go team! Perhaps the huge appetite for good news regarding carbon-free renewable energy is coloring the tech news coverage. The hype surrounding fusion energy lately has loosened the purse strings for research after many lean decades. Since money is a too convenient proxy for success, perhaps fusion research just seems more successful even to a relatively tech-savvy press corp. There is feedback at work here that could be unhealthy. We just described examples of trained scientists whose…enthusiasm?…helps drives a cycle. I’ll talk about this cycle and its pitfalls in a later article.?In the meantime, I’m looking for straight shooters. My kingdom for an honest skeptic!
O Brother, Where Art Thou?
While researching for this article I did find one articulate and credentialed scientist unafraid to provide reasoned critiques of NIF.?In 1995 Dr. Stephen Bodner published a paper suggesting that NIF might never ignite.?Using the most accepted definition of ignition, he is still correct.?When NIF recently approached the threshold of ignition, the New York Times quoted Dr. Bodner:
“It demonstrates to the skeptic that there is nothing fundamentally wrong with the laser fusion concept,”
It would seem there has been a change of heart…
Where Have All the Skeptics Gone??
Curious, I reached out to Dr. Bodner. It was a pleasure to discuss issues with someone who spent his career sincerely dedicated to the fusion energy cause. He continues to be influential (and skeptical!) in retirement. While he is truly impressed regarding NIF’s progress, he still believes the NIF approach is not suitable for fusion energy applications. I recommend reviewing Bodner’s broad-stroke description of the path to laser fusion power plants.?
Giant Leaps
While the APS article may be correct that the NIF result is a small step towards a fusion-energy reality, in the following sections I feel it is necessary to highlight some of the giant leaps that are still required.
Broken Records
NIF has had significant improvement in performance of late. This summer’s fusion yield jumped 8x from the previous record and 25x results from 2018. This is the good news.
The bad news is that one would need another jump of 100x or more to hope to build a power plant. On this graph indicating NIF’s recent progress, the bar representing the fusion yield necessary for a power plant would over 10 feet high! Worse news: Dr. Bodner and others believe that such very high gains are only expected from so-called direct-drive targets. Direct drive is where lasers hit a spherical fuel pellet directly. NIF, mimicking dynamics within an H-bomb, uses ‘indirect-drive’ where lasers hit the inside of a metal can that surrounds the pellet. ?
Lemonade Stand Economics
There is more bad news. NIF has done less than 200 ignition experiments in the last 10 years, whereas a power plant would take approximately a million shots per day! ?Like the cost of sugar when kids set up a lemonade stand, the cost of ingredients at NIF is quite a shock. For a power plant to be profitable, the fuel pellets would have to cost less than $0.10 each. Instead, the targets used at NIF literally have a pure diamond crystal globe inside a tiny golden can with double-glazed windows on each end, etc. These indirect-drive targets are estimated to cost 10’s of thousands of dollars…each.?
Nice Shootin’ Tex!
In a reactor, targets would have to be fired at great speed into the center of the fusion chamber. Simultaneously blasting lasers through both open ends of the tiny golden cylinder needed for indirect-drive makes precision targeting/focusing far more difficult than with direct drive. Neither would be easy.
Summary
This table summarizes just some of the giant leaps required to NIF’s physics, engineering and operations before a laser based fusion energy power plant can be considered.?While these numbers are daunting, it should also be emphasized that NIF isn’t even on a path to fusion energy. Nor should it be. NIF is focused on weapons research. Failing to make this distinction is counterproductive to the fusion energy effort.
Thanks only to honest and detailed discussions with a constructive skeptic, I have recently come to believe there may be a path forward for laser fusion energy. But I was also convinced that this path should not go through a weapons lab or use indirect-drive targets. For laser fusion energy to become a reality, it can not be an afterthought or a feel-good cover-story. It would require a dedicated facility funded only after open discussion of the giant leaps still needed in this area. Scientists and journalists committed to the long-term prospects of fusion energy would do well to avoid the temptation of feeding short-term fusion hype.?The journey to fusion energy will be difficult enough as it is without needless obfuscation of facts.
Professional Partner
3 年Excellent writing style, learning here and thank you. We better not hold our breath, and the hype out there is not helping. Is there any chance of some "breakthrough" new shooting or particle or long shot? Thank you for sharing.
Physicist at General Fusion
3 年Thanks for writing this excellent piece!
Radically rethinking how proteins and food are made. ?? Born at 317 ppm CO2
3 年Peter, thank you for the wonderful explanation so that even a biologist can follow.
Director of Product Management for Data Center Products
3 年Agree. We don’t need to establish energy independence by finding more ways to blow ourselves up. The research seems promising but the challenges are also palpable.