359 – Modern Fission Reactors

(average: 4.11)

Guest: Jacopo Buongiorno   Host: Markus Voelter   Shownoter: Andy Joiner

In this episode we take a look at newer generations of fission reactors, those that are currently being developed or researched. Our guest is Jacopo Buongiorno of MIT. We discuss some of the high-level goals of these new reactors, such as increased safety and efficiency, and then look at a few of the interesting new designs and how they realize these goals. We also briefly cover some of the policy arguments around keeping fission in the mix for combatting climate change.



Jacopo Buongiorno | Nuclear Science and Engineering | MIT | Advanced Nuclear Technology | Reliability | Decarbonization | Fission | Fusion | Nuclear Power Plant | Primary Energy Source | Turbine | Electric Generator | Grid | Condenser | Reactor Core | Uranium | Nuclear Binding Energy | Chernobyl | Meltdown | Cooling | Intrinsically Unstable | Radioactivity | Decay Heat | Redundancy | Passive Safety | Control Rods | Irradiated | 3-Mile Island | 3-Mile Island | Retrofitted


29 Responses to 359 – Modern Fission Reactors

  1. Teagle says:

    Really enjoyed to podcast. I appreciated the structure and you guys going down to the basics.

    I did keep expecting to hear thorium mentioned but maybe I thought that was more significant to the future of nuclear than it really is.

    I really didn’t mind the policy discussion. I think it’s impossible to decouple from the subject at large and actually important to inform the public of the reality of the technology.

  2. Markus says:

    I think thorium was mentioned as one of the molten salt reactors. But I am not 100% sure.

  3. Volker says:

    Very interesting. From all other sources talking about forth generation fission reactors I always understood that burning the existing nuclear waste was one of the most important advantages. Markus, maybe you want to put final repositories on your list for future episodes? I never really understood why there is so much resistance against having one close to your home as I imagine that they are very safe for some centuries. But aren’t they an expensive problem for millenia?

    Thanks for the great job you’re doing with omega tau!


  4. Martin says:

    Great episode with a good overview on the new technologies and developments. It once again confirmed to me that developments take very long time, considering that many of these topics are on the table for centuries. I also think that the technology will be essential in reducing the CO2 emissions, however, I found the reasoning concerning nuclear waste a bit too easy. Most of the listeners will have the technical background to understand the subject and there is no need for “political BS-talk” around the key aspects. But a simple “the cost play no significant role” as a solution to the waste question is a bit too easy. The subject is not only debated politically, but also technically. And unfortunately, too many mistakes were made in the past in this regard, also by scientists. It would be really interesting to have an episode on this topic specifically to also understand the problem in detail. As far as I know, there are also concepts to treat nuclear waste and produce elements that are much less radioactive and have much shorter half-life times? Anyhow, very interesting episode which I enjoyed tremendously.

  5. Markus says:

    Hi Martin,

    yes, I agree, I got the same impression that Jacopo wasn’t sufficiently technical/serious there. And I agree, some of his formulations were to glib. I didn’t want to challenge him there too much though, because we had a time limit and I wanted enough time to get to the technical stuff. I agree 100% that we should try to get an episode on waste management. I will try to find experts there … help is appreciated :-)


  6. Olaf says:

    There where in the past 3? years on Arte/3Sat at least two features about these points. One from an swiss? author about storage (Comparing Swiss, US…) and one about the thorium-reactors and why they lost against uranium. Unfortunalty I erased the disks with the records two month ago. But perhaps they are in the mediathek.

  7. Alex says:

    I too, would highly interested in an episode on the nuclear waste problem, since for me it is still the most difficult problem to tackle.
    In my opinion another point, which was only briefly mentioned was the availability of uranium, but I don’t have any knowledge in this area. For my outside perspective isn’t it just changing from one finite resources to the next, even if it could help with the CO2-Problem. Could it be, that we will run headlong in the next energy problem and should rather invest the scientific and industrial resources to renewables?

    But I must say, this episode did quite change my perspective on nuclear energy quite a lot. Thanks for that!


  8. Steve says:

    Loved the episode with a very good overview of the different reactors. Provided a real insight in the various reactors. I have been following the mixed salt reactors and the micro reactors with much interest for a while. I first got interested after hearing a podcast back in 2014 where Kirk Sorensen who is a co-founder of FLIBE (see https://flibe-energy.com/) presented a good overview of the history and the work being done on mixed salt reactors, see https://www.peakprosperity.com/kirk-sorensen-an-update-on-the-thorium-story/

    Would indeed love to have a future episode on the waste management and the work that is being done in Sweden and Finland to make the management of Nuclear waste possible.

    Keep up the great work

  9. Lewis Foster says:

    First time listener today and really really enjoyed it. You both came across as really nice, smart people genuinely enjoying the conversation. I did find it slightly amusing that at the end Markus sounded really tired. The closure and thanks to the guest could have been better but I think it was just the mental exhaustion of the discussion. I’ll be back for more!

  10. Markus says:

    A brief peek behind the scenes. I am not sure that I was actually tired, I don’t remember. But the reason why the ending is sometimes a bit strange is that before we end, I often discuss procedural stuff with my guests, such as whether they want to listen to the preview before I publish and such. During editing, I cut this stuff out, and the remainder then sometimes sounds strange in terms of the flow of the conversation. This was probably the case here as well.

  11. Rico says:

    On the issue of how nuclear can help with GHG emissions: I firmly believe it can’t and we shouldn’t go down that path. Nuclear power is extremly expensive compared to solar and wind. Even the direct costs are not competitve anymore, let alone the hidden costs that are caried by society (e.g. no legal need for insurance covering accidents, waste handling, etc). Solar can be produced at nearly 1ct per kWh. No nuclear power plant will be able to match that.
    Then there is the fact that humanity has not shown the ability to handle this technology in a safely manner. We have major accidents every 20 years which is just not an acceptable rate. And all other previous accidents were thought to be impossible. Nuclear is simply not safe and we have only been lucky that no major accident has happened in an area with a high population density. Although Fukushima was close, given another wind direction, the Tokyo metro would be another place today.
    So no, nuclear is not the way forward. Good news is, we are perfectly able to match all of our power demand with renewables.

    On the topic of waste: I strongly disagree with notion that we simply design “safe” containers, then dump them somewhere, close the hole and don’t have to deal with it anymore. There is science dealing with the question on how we can mark the waste so that future societies are able to spot the dangerous waste. There is no way for us to prove (in a scientific acceptable way) that our process of storing nuclear waste is safe in 1000 yrs or more. History shows us that we weren’t even able to do that for a few decades.

  12. Markus says:

    1) You say that nuclear cannot help with GHG emissions. But then you don’t explain why and pivot to …
    2) Price. Honestly, I have heard both, from both parties. It’s really hard to find out the “objective” truth, I suspect it depends on which costs you include. I will certainly also do an episode on solar in the near future I hope.
    3) Safety. I just disagree. I am sure already now climate change has caused more harm than the nuke accidents. And it will become much worse in the future.
    4) I admit that we didn’t cover that topic adequately. Wasn’t the idea either. But I am actively working on trying to organize an episode on this subject.

  13. Hey Markus,
    Thanks for this episode. I was really curious about it, as I saw it, especially as the nuclear-lobby is rising to a new level (they found out that climate-activist with shallow technical knowledge are perfect influencers at these “social”-platforms).
    As you already mentioned, you didnt feel like going hard on Jacobop and therefore I was missing some technical details but especially the risk assessment could have been much more in the focus.
    Nuclear Energy is a genius power source BUT ONLY if your willing to accept a “Super-GAU”. This is not neglectable by any redundancy or technical solution in the construction design (if everything goes wrong, it happens) and therefore is the main-issue. If not, we would have been using it already without any doubts.
    Therefore I would like to encourage you, as already mentioned by others, to do an interview about “nuclear risk assessment (2-split: nuclear waste and grid support). I will also try and contribute to tue preparations. Thanks in advance

    Maybe 3 more interesting aspects:
    – nuclear energy is told to be cheap but nobody knows how cheap. There is no real price transparency (especially including subsidies) as there are no laws requiring it. This always leaves room for doubt for both sides. Fact is, nuclear power plants (NPP) have always tried to produce for good margin (see hinkley point C) and therefore never in the interest of people and never close to their “real” price neglecting societal costs.
    – NPP are told to be grid supportive as they would be able to react fast on grid frequency drops. But in reality they are not used for it. As high pressure changes effects the all over stability of the construction materials (fatigue), connected to a high risk (nuclear accident etc)
    – MOST IMPORTANT: there are only a few big players in the business because of the high complexity of the technology and the costs concerning safety regulations. Revenues are therefore not distributed widely and the market entrance barrier is very high. Therefore its not a technology to help our current societal challenge (inequality) and fight power poverty.

    If you are interested in a talk about “modeling the energy transition to a 100% renewables” I would be keen to get you in contact with my colleagues from the RLI.

  14. Julian Endres says:

    Thats why big NPP dont go along with renewables in case of emergency.

  15. Markus says:

    Thanks Julian. Again, risk management was not the focus. The goal was to discuss some of the newer reactor designs. But I do agree that risk management is important. As a first step I will do something about nuclear waste. I already have on of the two guests I’d like to have on the episode confirmed.

  16. Markus says:

    Not sure I understand your comment in relation to the diagram.

  17. David Stevenson says:

    Great to hear an English language episode, I’ve missed you! Great subject, great interview, the tech aspects seemed pitched just at the right level, for me. Thanks Markus.

  18. Skip says:

    All the above comments have merit and for this listener and glider pilot (aka wing-nut) I would add that the interview was among the most important and educational non-aviation OT presentations to date. Why? Because this is the future of climate preservation for the planet and our species, imperfect as they are.

    And, Markus, you need never apologize for “too long” an episode.

    Rating: 5+

    Thank you,

  19. Jason Leaahy says:

    National Nuclear Laboratory and Leicester University UK are developing a method of extracting americium from plutonium nuclear waste and turning the americium into nuclear batteries that can power electronics on space ships for 400 years, recently a deal was signed with the South Korea Space Agency. NNL press release https://www.nnl.co.uk/blog/2019/05/03/uk-scientists-generate-electricity-from-rare-element-to-power-future-space-missions/
    Bristol University and spin off firm Arkenlight UK is developing radioactive carbon-14 NDB (Nuclear Diamond Batteries) from the graphite blocks in old retired nuclear power stations which can be used for a variety of applications including IoT, pacemakers, smoke alarms, sensors at the top of volcanoes, tv remotes. Great interview with Morgan Boardman Bristol Uni and Arkenlight https://newatlas.com/energy/arkenlight-nuclear-diamond-batteries/
    If you make an ep about atomic batteries he will be a good guess to interview. There should be an ep this year of Fully Charged Show on youtube with Dr Helen Czerski about NDB which was delayed in 2020 due to covid-19. I think Robert Llewellyn (actor who plays the android Kryten in classic tv sci-fi comedy Red Dwarf which is still being made, latest ep Mar 2020 check if you can watch old and new series in Germany on iTunes, Netflix, Google Play and Amazon) in the Fully Charged Show said 75% of UK Gov subsidies to the power sector is for nuclear with most of the money spent on storing nuclear waste so converting it into atomic batteries could save billions of pounds a year.

  20. Valerio Oddone says:

    Very nice episode. I liked the technical details and I agree that nuclear energy is in spite of all problems the best compromise fore the base load. The risk we take into account is way lower than the risks of the increasing CO2 levels and nuclear energy proved for decades to be by some orders of magnitude safer than coal, even if you include fatalities from the Chernobyl accident (which is quite silly since we have no nuclear power plants with positive vacuum coefficient left).

    I hear for the first time that fast reactors are loosing of interest, and I understand the argumentation that uranium is just to cheap at the moment.
    Still there were and are some successful fast reactors to mention, like Phenix in France (250MW and 37 years of operation) or BN-600 in Russia (540MW and in operation since 1980). Several companies are investing new projects, see Terra Power, Flibe Energy, and the indian FBR-600 (in construction). It would be nice to have a second episode on these technologies, as well as about thorium reactors, as mentioned by others.

  21. Felix says:

    As always, great content and indeed very relevant! In my opinion, when talking about fission, one needs to consider the mining of uranium or other raw materials. From what I know, it’s a very dirty process (regarding the environment in general and especially the ground water in the mining region) and it is only rarely even brought up as an argument. Everybody talks about nuclear waste but nobody realizes that acquiring the stuff in the first place is quite a big problem already. Of course, at the moment there is probably no way around fission but we should definitely strive towards a future that is less dependent on exploiting our soil (like with coal, gas and oil).

  22. Markus says:

    Long long term I totally agree.

  23. Peter says:

    While the physics and engineering of nuclear power plants looks good on paper and sounds superficially convincing in a podcast, the safety aspect never seems to work out in real life. I might be wrong but my impression is that almost none of the existing reactors seem to have worked without any incidents, some of which were supposed to be impossible from the design. Some were because of manufacturing flaws, some due to human error, or other unplanned external causes. Many running facilities and companies were also involved in rather severe cover-ups.

    For example, the pebble bed reactor — that I think that Jacopo described as inherently safe — was developed in Germany as the AVR experimental reactor and then built as the THTR-300. Actually operating it was such a disaster that is was decommissioned after only a short while.

    One of the questions was about making sure how the reactor is automatically/passively cooled. But the important point there is that one has to guarantee that for a long time, not just for an hour but actually up to months, depending on the reactor type. If I remember correctly, that was one of the problems in Fukushima.

    I hope that in the future episode on nuclear waste you will also discuss the remains of decommissioned nuclear reactors. To my knowledge, not even one of those in Germany is fully disassembled yet.

    Now I also visited Jacopo’s website. He is “TEPCO Professor of Nuclear Science and Engineering”. Does that stand for “Tokyo Electric Power Company”? Then I’m not surprised by his rather optimistic (naive?) attitude. Would have been nice to know from the outset.

  24. Markus says:

    The nuclear waste episode will not cover decomissioning. That’s another topic. But may be another interesting episode. Would you have suggestions for guests?

    Yes, the TEPCO thing. I realize Jacopo was biased. I knew that before. But it is very hard to find people who know what they are really talking about, who are deep in the technology and engineering, who are not in favor of that technology. Is he “biased” because he has the job? Does he have the job because he genuinely believes in the approach? Hard to untangle. And that professors are sponsored by (related) industry is rather normal in the US. With this I don’t want to say that I couldn’t possibly have found a less biased person. But it’s really hard.

  25. Ralph Benton says:

    Even as a fan of nuclear I am dismayed at the scale of a serious accident. In a nutshell, when a nuke plant goes wrong, it goes very very wrong. While Jacopo is correct when he says that no one would operate a reactor as unsafe as Chernobyl, that implies that everyone assumed Fukushima was a safe design. Now that we know PWR reactors aren’t as safe as the designs he describes, we assume that nextgen reactors will be safe. Yet history, complexity, and statistics suggest that another massive failure is inevitable. When that failure occurs, we will be left dealing with another multi-generational clean up that leaves large areas uninhabitable.

    Obviously losing 100 or 1000 sqkm to radiation is better than losing 1,000,000 (or more) to sea level rise. But we should not think that we will never experience a catastrophic nuclear disaster.

  26. Philipp Huber says:

    Can we have a specific discussion about Thorium in molten salt reactors?
    This seams to be a silver bullet! Too good to be true?
    + extreme inherent walk-away safety (stops reacting if too hot, stops reacting if too cold)
    + burns nuclear waste and transforms it to much less waste which is only radioactive for 300 years instead 10000+ years.

    – molten salt containment not completely solved yet because of high working temp?

  27. Andrew Cowenhoven says:

    As a long-time nuclear power skeptic I found myself swayed by the episode. This was mostly from the unescapable fact that Markus stated at the outset: we, as a society, will never “conserve” our way out of this environmental mess we are in. Where does that leave us? We need more discussions like this.

  28. Penultimate says:

    The guest’s authoritative tone is actually borne of hubris and 20/20 hindsight. Of course he has designed out all PAST possible accidents, any moron can do that. But he has NO way of foretelling all FUTURE possible failure modes, any more than the designers of Three Mile Island or Chrnobyl or Fukushima. Every one of those was born of something completely unforeseen, or deemed a “small probability”. This guy is not preternaturally smarter than all of them just because he happened to be born last. A tsunami hitting the reactor? Absurd! Any engineer who demanded they account for such a thing would be fired. BUT IT HAPPENED. Nuclear warships are tolerable because we need relatively few of them, there are ENOUGH highly motivated and smart people to run the things, and the risk of operating them way out at sea is worth it. But as long as power plants are run by guys with C averages in engineering from the University of Delaware, they will be too dangerous.

  29. Marc says:

    I am not convinced. Nuclear may be the stop-gap measure (incurring lots of technical debt) we may need to halt the climate catastrophe in the near future. Apart from that, it has proven to be a way to dangerous method to boil water.

    But wouldn’t it be interesting to have a followup episode then about the relative cost of (slowly) killing people and the environment by means of fossil fuel (how many death/decade through pollution etc.) vs. the more spectacular human and environmental cost caused by the well known nuclear accidents and the long term issues of waste treatment and storage?

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