Reasoning about Nuclear Energy

I try to present facts and logic and solutions rather than just opinions.

Please send any reasoned disagreements to me. If your facts and logic are convincing, I'll change my mind !       

Nuclear in general

Stuart Gary's "Fusion vs fission: clean, green nuclear energy technologies explained"

Why nuclear energy is bad:

From former US Navy nuclear technician on reddit 5/2017:

I eventually changed my mind on [favoring nuclear power], however, for essentially one reason. I don't think humans are ready for the long-term responsibility of waste storage. The US government is the most powerful organization humans have ever created, and they're responsible for the regulation and ultimately, the handling of a very large quantity of nuclear waste products for the foreseeable future (and much, MUCH longer) ... yet they can't even pass a budget for even a single year. If our most powerful human institutions can't plan even one year ahead, we have no business creating substances that require us to be responsible for their safeguarding for millennia.

I've been called "anti-science" or even a Luddite for pointing this out on Reddit in the past. I can only assure you that this isn't the case. You'll have to take my word for it that the Navy isn't typically in the habit of training Luddites to operate nuclear reactors on board their submarines, and people that "just don't understand science" don't make it through Naval Nuclear Power School. And while I understand the dangers of climate change as well, I don't think trading one long-term problem for another is the solution. I think we just have better options at this point. I'm 100% behind further research into fusion, and even thorium fission reactors, but I think our best bet, for now, is renewables and more research. Maybe one day we'll find the solution to rendering the waste completely inert, but until then, building more nuclear capacity or continuing to operate at current levels makes no more sense than taking up smoking on the assumption that lung cancer will be cured before it kills you.

The video [posted by someone else] says that we've yet to build a deep storage facility for nuclear waste, but this isn't technically true. We've yet to complete it, but one is currently being built in Finland. Even this ambitious project, the only of its kind (that I'm aware of), which has long been touted as the ultimate "long-term" solution for the waste problem, has its problems.

I'd encourage anyone who's actually interested in this topic to watch the excellent documentary on Onkalo (the storage facility in Finland) and the problems with the long-term storage of nuclear waste products in general: Into Eternity.

From Wikipedia's "Economics of nuclear power plants":

[Decommissioning:] In the United States, the Nuclear Regulatory Commission (NRC) requires plants to finish the process within 60 years of closing.


The cost of the Fukushima disaster cleanup is not yet known, but has been estimated to cost around $100 billion.


In terms of nuclear accidents, the Union of Concerned Scientists have stated that "reactor owners ... have never been economically responsible for the full costs and risks of their operations. Instead, the public faces the prospect of severe losses in the event of any number of potential adverse scenarios, while private investors reap the rewards if nuclear plants are economically successful. For all practical purposes, nuclear power's economic gains are privatized, while its risks are socialized".
Stefan Nicola and Julie Johnsson's "Nuclear Decommissioning Surge Is Investor Guessing Game"

From Jerry Taylor's "Nuclear Energy: Risky Business":

[Published 2008, but some points still valid today.]

... electricity markets have a very peculiar pricing mechanism that makes it harder for nuclear to maximize returns compared to gas-powered or other plants. In essence, there are two electricity markets: a market for base-load power (electricity sold 24-hours a day) and a market for peak power (electricity sold as needed during peak demand periods like hot summer days). Much of the demand for new power - and thus much of the profit available to investors today - is found in the peak market. But nuclear power plant construction costs are so high that it would take a very, very long time for nuclear facilities to pay for themselves if they only operated during high demand periods. Hence, nuclear power plants are only profitable in base-load markets. Gas-fired power plants, on the other hand, can be profitable in either market because not only are their upfront costs low but it is much easier to turn them off or on unlike nuclear.


... investors in new nuclear power plants are making a multi-billion dollar bet on disciplined construction schedules, accurate cost estimates, and the future economic health of the region. Bet wrong on any of the above and the company may well go bankrupt. Bet wrong on a gas-fired power plant, on the other hand, and corporate life will go on because there is less to lose given that the construction costs associated with gas-fired power plants are a small fraction of those associated with nuclear plants.


Investors are also wary of nuclear plants because of the construction delays and cost over-runs that have historically plagued the industry. For instance, the Areva/Siemens nuclear power plant being built for TVO in Finland - the first nuclear power plant to be built in a relatively free energy market in decades - once scheduled to be operational within 54 months, is now two years behind schedule and 60% over budget. Nor have these construction delays had anything to do with regulatory obstruction or organized public opposition.

If nuclear power plants are so uneconomical, how then to explain the blizzard of permit applications for the construction and operation of new nuclear power plants that the Nuclear Regulatory Commission has received? Easy: These applications cost little and oblige utilities to do nothing. Industry analysts maintain that federal approvals will not translate into actual plants without a federal promise to private equity markets that, in case of default by power plants, the taxpayer will make good on the full sum of all bad nuclear loans.


Nuclear supporters often counter that construction costs would be a lot lower if regulators didn't impose insanely demanding safety standards, byzantine and time-consuming permitting processes, or endless public hearings, any one of which could result in the plant being stopped in its tracks. Investors would also be more likely to invest, we're told, if there were a high-level waste repository in place or more political support for nuclear power.

I would love to tell that story. I do, after all, work at the Cato Institute, and blaming government for economic problems is what keeps me in business. But what stops me is the fact that those complaints are not echoed by the nuclear power industry itself.


Given all of this, how do France, India, China, and Russia build cost-effective nuclear power plants? They don't. Government officials in those countries, not private investors, decide what is built. Either these governments build expensive plants and shove them down the market's throat - or they build shoddy plants and hope for the best.

Nuclear energy may well be safer, in terms of deaths per year, than other forms of energy. Solar installers fall off roofs, wind-generator maintenance people fall off wind-generators, coal miners die from accident or illness. Of course, there are some deaths in the uranium mining and processing and transportation industries. And some people died from the accidents at Chernobyl and Fukushima.

Nuclear energy may emit less greenhouse gas than solar energy ? Seems unclear. For example, if you look in Wikipedia's "Life-cycle greenhouse-gas emissions of energy sources", you find three sets of numbers, the first showing utility-scale solar emitting 4x as much GHG as nuclear, second showing solar PV emitting about 3x as much as nuclear, third showing solar PV emitting 1/2 as much as nuclear. And in the first set of numbers, emission for solar PV has a range (min to max) of 10x and nuclear has a range of 30x. So I'm not sure what to think.

Nuclear energy may well be better than coal energy, which directly pumps pollutants (including CO2, acid-forming chemicals, radioactive materials, particulates, mercury and other metals) into the air, leaves toxic ash/sludge afterward, and often involves massive environmental damage from mining, and health damage to miners. But "at least we're better than COAL" is not a ringing endorsement.

Some new nuclear reactor designs may fix some of the problems with current nuclear power plants. But we're not using those new designs yet, and may not be for a couple of decades to come. Many of these "new" technologies or designs have been studied or prototyped for 40+ years now, and still haven't become commercial. MSR experiments were done at ORNL in 60's, thorium has been studied by US in 60's and many countries since 70's and operated in Germany in the 80's (THTR-300), fusion has been worked on with big money since the 70's. We'd probably be better off investing in new renewable energy technologies rather than new nuclear technologies.

Use of nuclear energy may well be necessary for decades to come. Only certain types of renewable energy (geothermal, tidal) can serve as "baseline" (continuous, dependable) energy, until some storage mechanism (pumped hydro, stored heat, flow batteries, etc) is used along with variable renewable sources (solar, wind, etc). But there continues to be great progress made on development of new storage and improvement of solar photovoltaic power. Other technologies (wind, hydro, etc) don't have as much room for improvement, and still others (nuclear, coal) offer the chance of improvements in safety or pollution but maybe not efficiency or cost.

Shauna Theel's "Myths And Facts About Nuclear Power"
Wikipedia's "Economics of nuclear power plants"
Ian Sample's "Fukushima two years on: a dirty job with no end in sight"
Mark Cooper's "The Economic Failure of Nuclear Power ..." (PDF)
The Economist's "Half-death"
Joe Romm's "Why James Hansen Is Wrong About Nuclear Power"
Mark Diesendorf's "Renewable energy versus nuclear: dispelling the myths"

CANDU from discussion on reddit 5/2017:

There are a few reasons why we don't see more:


They are also really expensive to run. The maintenance costs are huge; there are so many subsystems to maintain. Which feeds into the tritium problem.


CANDU reactors are not perfect. It costs $300M to fill a CANDU reactor with D20. And in CANDU reactors, fuel gets shuffled around a lot and that can add to proliferation risk in a different way than what you mentioned with H3.


LFTR (Liquid Flouride Thorium Reactor) from discussion on reddit 1/2014:

I think one of the biggest problems is not feasibility, but cost. Development of new nuclear power systems is extremely expensive and comes with incredible amounts of regulation. Power companies already have proven designs and don't have a lot of incentive to invest in unproven designs that will take decades to be profitable, assuming that there isn't some inherent flaw being overlooked that ends up making the idea infeasible. It's not a big conspiracy, just economics.


To add: LFTR would require a complete rewrite of the regulatory rulebooks. The NRC is very familiar with PWR designs and even sodium fast-reactors. But molten salts? They haven't the slightest idea. It is too different.

Then there is the reprocessing issue. As it stands now it is a no-no. Not in law but by regulation. Getting the well-understood PUREX processing going for current nuclear waste is damn near impossible. LFTR requires a brand-new fluoride volatility Uranium separation system, a vacuum distillation step to recover the salt, plus possibly a pyroprocessing step to keep the actinides out of the waste stream. The NRC hasn't the first idea how to regulate any of that. Again, because it is too different.

You would have to build it all (reactor, reprocessing, power systems, etc) small-scale and test it for years, then have the NRC write the regs, then you could finally scale up the thing for commercial power.

It is a technology that is in its infancy and decades away from commercial production if it was to be pursued. But if we ever figure out how to build and operate it cheaply ... sheesh ... we wouldn't need anything else. Medium-lived waste stream with inexhaustible fertile material.


Based on the way the NRC has been lately, it would take them over a decade just to figure out how to make rules for a LFTR even with unlimited resources. Of course this includes all the anti nuclear lawsuits that will hold up the process.


Most of the obstacles facing LFTR are not in fundamental physics, however they are more political or cultural in nature. Most of the nuclear industry as well as most nuclear engineers are trained to handle solid fuel elements. LFTR's, on the other hand, operate primarily in the fluid phase like a chemical plant, at much higher temperatures. As a result, much of the actual day-to-day skills of nuclear engineers do not translate. Besides the fact that light water reactors and LFTR's both rely on nuclear fission, the technologies are very different from the engineering perspective.


The biggest issue with the technology that I can see is that it doesn't seem to offer any massive benefit over modern reactors, at least in the near term (the fuel supply issue makes it more tantalizing in the really long (100+ years) run, though).

One compelling advantage that it seems to offer versus a modern light-water thermal reactor. It seems much, much harder to catastrophically break the primary plant, thanks to the lower pressures involved. On the flip side, it seems to have more potential for lower level radiological problems, but as long as those can't make hundreds of square miles uninhabitable, that may be a good tradeoff.

The big disadvantage that I see in the LFTR is the inability to recover from some types of plant casualties gracefully. For instance, a steam rupture or other massive, secondary-induced over-power transient could cause the coolant to freeze, which would easily drop an entire loop, and possibly put the entire plant into a complete loss of coolant flow (and potentially dead-heading and then burning out your pumps, making it totally impossible to recover from). The answer to that seems to be just dumping the combined fuel/coolant mixture into an unmoderated holding tank, which seems like it would work, but breaching your primary containment boundary is hardly a good solution to a reactor plant casualty, imho.

In short though, it seems like every other thought-out form of nuclear power: possible, viable, but not without some risks, and not nearly the panacea that its proponents make it out to be.

From Edwin Lyman (expert on nuclear terrorism and nuclear safety, works at UCS, doctorate in physics) on reddit 3/2014:

[About LFTR:] We are aware that there are many types of reactor designs other than light-water reactors, the current standard. These concepts all have advantages and disadvantages relative to light-water reactors. However, most competitors to light-water reactors share one major disadvantage: there is far less operating experience (or none at all). Molten-salt reactors, of which the LFTR is one version, are no exception. The lack of operating experience with full-scale prototypes is a significant issue because many reactor concepts look good on paper - it is only when an attempt is made to bring such designs to fruition that the problems become apparent. As a result, one must take the claims of supporters of various designs with a very large grain of salt.

With regard to molten-salt reactors, my personal view is that the disadvantages most likely far outweigh the advantages. The engineering challenges of working with flowing, corrosive liquid fuels are profound. Another generic problem is the need to continuously remove fission products from the fuel, which presents both safety and security issues. However, I keep an open mind.

From /u/theskepticalheretic on reddit:

We built one in the US at Oak Ridge national laboratory in TN. The reactor experienced multiple accidents, some fatal, and was primarily an experiment in the feasibility of the design. The biggest challenges to widespread adoption are techniques used to make the components, chemical separation of 'neutron sinks' (daughter products that slow to stop the reaction like protactinium), and the construction materials. Further, the medium used to move the heat for power production is nasty, nasty stuff. Molten salt is highly corrosive, making containment of the heat transfer medium very, very difficult (which was coincidentally what many of the facility accidents involved).

From /u/cark on reddit:

[About thorium in general:]

... there is the issue of supply chain. Getting from uranium ore to the uranium pellets used in nuclear plants is a whole industry. Much R&D went into that. It is also a profitable industry.

The startup cost for a new supply chain is enormous. You need the ore, the thorium extracted, then conditioned, and on top of that you need the power plants to sell it to. A bit of a chicken and egg problem if you will. To make any of it commercially viable. Each of these steps requires costly R&D, then a lot of hardware investment.

Public funding is often required for such high cost research. For the uranium supply chain, there was a will. Not so much for thorium.

From /u/whatisnuclear on reddit:

[About why don't we have thorium power:]

The main reason is momentum. Nuclear energy isn't like software in that you can just have rapid transformations overnight. The industry moves at a snail's pace in innovation these days. It's so hard to even make small changes to conventional reactors with all the people suing and all the regulators being extra careful to protect the public. The Navy developed light water reactors to propel submarines as a war-time need. This development transferred over to industry and we've kinda been stuck with it. Forays into advanced reactors were made. The USG spent a lot of money on liquid-metal cooled reactors, but they became politically unpopular and very over-budget and were eventually axed by Congress. Smaller efforts were made to develop molten salt reactors that are good with Thorium. Reasons for their cancellation have been quoted as:
  1. The existing major industrial and utility commitments to the LWR, HTGR, and LMFBR (AKA other advanced reactors).

  2. The lack of incentive for industrial investment in supplying fuel cycle services, such as those required for solid fuel reactors.

  3. The overwhelming manufacturing and operating experience with solid fuel reactors in contrast with the very limited involvement with fluid fueled reactors.

  4. The less advanced state of MSBR (thorium) technology and the lack of demonstrated solutions to the major technical problems associated with the MSBR concept.

Source: AEC's "An Evaluation of the MSBR" (PDF) (1972)

Nuclear innovation takes a very long time, lots of money, and very serious commitment. It's just not popular enough to get these in current democratic societies.
From /u/Versac on reddit:
It's not my specialty, but last I heard there still wasn't a good answer to the problem of neutron embrittlement without unacceptably compromising operating temperature, just to name one issue. I suppose I'm confused as to why you're attributing the lack of commercial thorium to industrial momentum when there are still significant technical issues. This is still experimental technology.

From /u/DropBear25 on reddit:

Nuclear engineer here - it never ceases to amaze me how often people keep repeating this idea that thorium is this magic bullet fuel and even worse that it would all just magically be ok if not for evil governments wanting to make plutonium. The engineering challenges to make a profitable thorium have not been overcome. End of story. It's a totally different reactor fuel cycle that requires special designs to be functional, the practicalities of which would be a huge investment. You have the potential to create some really nasty transuranic isotopes as part of the fuel cycle and also major sinks for neutrons which if not dealt with properly mean your reaction isn't sustainable.

Tinkering with it in government-funded test reactors is one thing, a profitable commercial reactor is something else. And if you're the person trying to fund these things you're going to go with the design that has a proven track record. I'm working on the new UK reactor and it's going to cost an estimated £16B to build, and that's for a reactor that's already largely designed and was only an evolution of standard pressurised water reactor technology in the first place. These things aren't cheap.

I'm all for science advancement and the above is the exact reason why public funding of this stuff is important because it shouldn't be all about the bottom line when you're talking about the future of civilisation, but people seriously have to stop oversimplifying the rhetoric on thorium.

From /u/bigmike827 on reddit:

Oh look, OP has stumbled upon Thorium. You know, OP, 5 years ago I found similar numbers and watched similar documentaries. I decided Thorium and nuclear would save the world and that I should dedicate my life to helping in the effort. 4 years later and hundreds of hours of studying I finally got my degree in nuclear engineering. I'm still all for nuclear and how it will ween us off coal, petroleum and natural gas, too. But f*ck thorium. F*ck the people who want it to happen. F*ck the people obsessed with it and f*ck the people halting research and development. Thorium is next to impossible to control, next to impossible to burn efficiently, and next to impossible to refine.

Nothing short of a perfect reactor made of next-next-next-gen materials would be able to make Th useful, let alone efficient.

So please, OP, don't let the idea of thorium make you hopeful. We'll have perfected fusion before we can handle thorium and molten salt reactors.

From /u/whatisnuclear on reddit:

[Why do we hear about thorium all the time (at least on reddit):]

Ooh I can totally answer this with my non-nuclear knowledge. My buddy Dave sent me this book once that explains why stories like the Thorium one stick. It says that to have a sticky message, the message should be:
  1. Simple: "Put this fuel in a reactor and all problems of nuclear go away"

  2. Unexpected: "Hey there's a energy source that solves all our problems that you've never heard of!"

  3. Concrete: "All you have to do is switch fuels from uranium to thorium!"

  4. Credible: "Tons of national lab scientists actually proved it works in the 60s"

  5. Emotional: "The only reason we don't do it is that the powers that be are holding it back, but we can fix this!"

  6. Story-filled: "We only don't have it because it can't make bombs" is a common story (albeit false)

As you can see, Thorium fits all the needs of a sticky story. Everyone knows we have an energy problem so when this pops up, it captures people. As I've written a lot, most of these one-liners are nuanced and often misconceived.

From /u/Hypothesis_Null on reddit:

> Why aren't we using one of the many more efficient
> and safer reactor designs (including thorium) ?

A short and incomplete answer is that we've made essentially one type of reactor for commercial use for the last 50 years. That's 50 years of operating hundreds of plants, that have let them identify points of failure and design redundancies and minimum tolerances to make them safe.

Right now building a nuclear plant is a very risky proposition just from an economics standpoint. And that's building a reactor you know will work. There are hundreds of problems that could be run into building the first commercial version of something like a Thorium plant. Other reactor designs can be more efficient - and at first glance you'd think that would provide some economic incentive to try the new models.

But this is where nuclear's prime advantage works against itself, so to speak. The cost of running a nuclear reactor is almost entirely running all the personal and safety mechanisms and general operation. The fuel cost is a very tiny fraction of operating costs. This is good, because it means fluctuating fuel prices don't really impact electricity prices, like they can with coal and oil. But it also means that a more efficient plant doesn't give much of a profit advantage.

TL;DR The current type of reactor we have comes with 50 years of experience, making them 50 years safer and 50 years more predictable. Because fuel costs are so tiny compared with the overall cost of running a nuclear reactor, a design with more efficient use of fuel doesn't really add to the bottom line enough to justify the risk.

From /u/dizekat on reddit:

Pretty much any thorium breeder reactor design could just as well run off depleted uranium instead (which costs nothing, i.e. a lot cheaper than thorium), getting similar mileage. So if someone's focussing on thorium in particular, it is a BS conspiracy theory.

The reason those reactor designs aren't used are complex, mainly having to do with fuel costs being only a small fraction of reactor operational costs; if you reduced fuel costs to zero but increased maintenance by a few percent due to more corrosive environment, you'd be worse off. Reducing costs is all about using materials that are least corrosive and most chemically straightforward (and for which there exists experience), hence boiling water trumps everything. Yes, you can set up a reactor that will need less uranium and/or could use thorium; the advantages of such are very easily negated by even a minor increase in failures requiring maintenance.

Stainless steel in hot water is a very well-studied topic. Materials in a mixture of fluorides of half the elements from the periodic table are not, not to mention that it is far more complex chemically than water. Materials in molten sodium are not either, but at least you don't have half the periodic table attacking your pipes.

From /u/choppedbeef on reddit:

If you're asking why we aren't switching over to thorium today, cost and technology are the two main prohibiting factors. If a business were to build a new reactor today, they would likely want to choose a well-understood design that they knew they could get NRC approval for, that operators and engineers have experience with, and that uses a fuel that can be obtained through an existing supply chain.

If you're asking why humanity decided to pursue U-238 water-cooled reactors instead of LFTRs early in the developing of nuclear power, the short answer is that it is much easier to obtain material for nuclear weapons from the waste products of a U-238 reactor than from those of a thorium reactor.

From /u/whatisnuclear on reddit:

> Are these advantages of Thorium over Uranium true ?
> 1- Thorium reactors can't melt down as catastrophically.
> 2- Thorium can't be turned into nuclear weapons in the
> same way that Uranium can.
> 3- We have lots of Thorium basically just sitting
> around as it was a byproduct of mining or something.
> 4- The moon has lots of Thorium so it would be ideal
> power generation technology for a lunar base.

Those are almost all the points we answered on our Thorium Myths and Misconceptions page.

TL;DR is:
  1. Low pressure reactors like Thorium-MSRs and a bunch of uranium fueled advanced reactors have major benefits over conventional water-cooled reactors in passive safety. If you put thorium in a regular reactor, it would be basically as catastrophic.

  2. False. It needs a different mechanism but it can definitely be turned into a nuclear weapon.

  3. True. Also true for Uranium. We can run the entire USA on pure nuclear for 200 years using the depleted uranium sitting around as cold-war enrichment tails if we used breeder reactors. So, it's an advanced nuclear thing, not uniquely a thorium thing.

  4. Haven't looked into it. Definitely possible. But a lunar base will probably start small. A nuclear submarine powers itself for a good 30 years on one small batch of fuel so it may not be necessary to set up mining infrastructure on the moon for the first few lunar bases.

From /u/totallylumberjacked on reddit:

> Why would a MSR be cheaper than an
> existing fission reactor ?

With a pressurised water reactor the fuel coolant needs to constantly be under like 100 bar of pressure. The architecture of the plant and the safety systems is all centred around what happens in the unlikely (but non-zero) chance that containment is lost. For example, the containment building is about a thousand times larger than the actual reactor itself because of the volume change from water to steam. The reactor casing needs to be 8 inch thick Hastelloy cast in one piece, no chance of welding. And the engineering tolerances are necessarily extreme.

Contrast this with an MSR system. At ambient pressure, so the reactor vessel can be far thinner and manufactured in a factory to be shipped out to where it's needed. A clean salt loop is run through the reactor out to a heat exchanger, where it then uses a steam turbine basically identical to something you'd find in a coal or gas power station. And because this type of design can be made in a factory, that means standardisation and economies of scale, compared to the current clusterf*ck of nuclear where seemingly every new plant (outside of China anyway) is individually designed, all special snowflakes with insane cost overruns.

Physics Central's "Thorium Nuclear Power"
Nick Touran's "Myths and Misconceptions about Thorium nuclear fuel"
Wikipedia's "Liquid fluoride thorium reactor"
Wikipedia's "List of thorium-fueled reactors"
Noel Wauchope's "Don't believe thorium nuclear reactor hype"
Physics Stack Exchange discussion
Jan Beranek's "Exposing the thorium myth"
ThorCon page explaining some of the technical issues
Union of Concerned Scientists Statement on Thorium-fueled Reactors (PDF)

Richard Martin's "China Details Next-Gen Nuclear Reactor Program"


Most of this applies to "big" fusion, a big reactor producing heat to drive a steam plant and electric generator, similar to today's fission and coal power plants.

If we ever get a huge breakthrough and someone invents a non-thermal fusion process that produces electricity directly, that would change everything.

Problems with fusion power:

From /u/Rannasha on reddit 10/2015:

Barring any unprecedented breakthrough, we're still very far (read: decades) from using nuclear fusion in a commercially viable manner.

We can already do fusion in experimental reactors. That's not new. We can also do fusion in a way that more energy is produced than is used in H-bombs. The problem is combining the two :)

A nuclear fusion reaction is rather hard to achieve and the essence of the problem is one of scale: The larger and more extreme the setup, the higher its efficiency. Current experimental reactors are too small to produce more energy than they consume. So the goal is to make a reactor that is bigger and operates at even higher temperature and pressure to go beyond the threshold of "Q = 1" (Q is the ratio between output and input energy, if Q > 1 then more energy is produced than consumed).

The current big project is ITER, this is planned to be the first fusion reactor to achieve Q > 1. The design goal is to reach Q = 10. But targets for continuous operation are only in the order of magnitude of hundreds of seconds (several minutes). Large parts of ITER and supporting infrastructure are currently being built in southern France. The project is scheduled to have its first plasma operations inside the reactor in 2020 and start fusion reactions in 2027.

But these are just schedules and delays can't be excluded since there is a lot to figure out still. The conditions inside the fusion plasma will be unlike anything we've made so far and even though magnetic fields will be used to prevent the fusion plasma from touching the vessel walls, making a reactor vessel that can withstand such stresses and still allow for energy to be extracted is a challenge, to say the least.

And while ITER is designed to generate more energy than it consumes, it's still very much an experimental device, set up for scientific purpose and not commercial application. The followup to ITER, called DEMO, is a prototype of a potential commercial plant built on the same principles as ITER, but slightly larger. Its very tentative schedule has first operation starting in 2033, with an upgrade/expansion already planned afterwards and the second, final phase of operation starting in 2040. But this very strongly depends on whatever we learn with ITER. And DEMO is still a demonstration model, not something that will be mass-produced.

Next to ITER and DEMO, which will use a technique called "magnetic confinement fusion" in a "tokamak reactor", there are several other avenues being explored. The donut-shaped tokamak reactor has an alternative in the so-called stellarator, which also uses magnetic fields to confine the plasma. In addition to magnetic confinement, fusion has been achieved using inertial confinement, which essentially involves a fuel pellet being forced to implode due to exposure to lasers, causing the outer layers being pushed inwards and confining the fusion reaction in the inner layers of the pallet.

All these techniques work, but none work at an efficiency that allows for commercial application. Currently tokamak reactors are in the lead when it comes to scientific attention, as evidenced by the ITER megaproject, but the jury is still out on what'll end up winning the race.

You hear cold fusion being mentioned from time to time as an easy and affordable alternative that does not involve effectively putting the sun in a small box and hooking it to the powergrid. In the late '80s there was some buzz about scientists allegedly finding fusion reactions taking place in conditions close to room temperature.

However, these findings were quickly disproven. These days, there's still a fringe community that revolves around the notion that cold fusion is possible in the way that was described back then. They also use the term "Low Energy Nuclear Reaction" (LENR). From time to time, some news article appears claiming a new device delivering practically free energy using something related to cold fusion / LENR.

Unfortunately, there has been no independent scientific proof of such a device actually delivering on its promises. When tests are being published, they're often of very poor quality, done by people affiliated by the creator or done without the researchers having full access to the device (At one point a test report described a cable being attached to the device without the researchers being allowed to see where the cable lead or to unplug it).

So for now, cold fusion / LENR is fringe activity that is riddled with scammers and people that are a bit too trusting. If cold fusion or something similar would be possible, it would be the holy grail to solve the energy puzzle. Because while "regular" nuclear fusion is a perfectly achievable process, actually getting useful power out of it is a large challenge it's unlikely that it will be the source of widely available, virtually unlimited clean energy this century.

From discussion on reddit:

Why is fusion such a big deal when we already have fission-based power plants?

From /u/crnaruka:

The short answer is that fusion power can potentially give us energy more efficiently than what is achievable using fission, it relies on a far more abundant source (hydrogen vs. uranium), and most importantly it avoids the risk of catastrophic meltdowns and the hassle of dealing with mountains long-lived radioactive waste. For this reasons fusion could truly be the definitive solution to the world's energy needs, producing almost unlimited energy in a fairly safe manner. The problem is just getting the damn thing to work ...

Now let's look at these potential benefits a bit more closely. The most striking advantage of fusion when compared to fission is that fusion can give you a much bigger bang for your buck (more energy per mass of inputs). ...

Another major advantage of fusion over fission is when it comes to safety and waste management. Carrying out controlled fusion is actually very, very, hard, which is why there is still not practiced on a mass scale. Essentially for fusion to occur at all, conditions need to be just right, or else pretty much nothing will happen. However, from a safety standpoint, this situation presents an advantage. Unlike nuclear fission where runaway reactions can lead to a meltdown, this simply couldn't happen with fusion. In addition, the reaction products are far more easily manageable for fusion power than is the case for fission. The reason is that while fission produces a sludge of long-lived radioactive waste, fusion generally only results in the production of helium (which is utterly inert), and some tritium. While tritium is radioactive, its short half-life (~13 years) makes its handling far more manageable.
From /u/VeryLittle:

This is spot on. Everything about the fuel is cleaner and safer.

The components and waste don't stay dangerously radioactive as long. The fuel is literally hydrogen - you can get it from water. It's not like turning a mountain upside-down to get uranium ore.

In plasma confinement reactors your reactor won't melt down. If there's a breach the plasma expands and cools and the reaction ceases. As you said, the only major risk is a tritium leak. Since it's hydrogen it forms water, and you don't want people drinking tritiated water. While it's harmless outside your body, beta decays inside your body are bad news.

One thing that can be said for fission though is that the "sludge of long-lived radioactive waste" is often the only source of a lot of those isotopes on earth, and many of them have useful applications. Traditional fission reactors can produce Molybdenum-99 which has a half-life of days and produces Technetium-99m. That 'm' means it's metastable and spits out a gamma ray, so it makes a great radioactive tracer for medical imaging. It works like an X-ray, except the gamma rays are originating inside your body. There's really no other source for this stuff, and with such a short half-life it can't effectively be stockpiled.

From /u/Hypothesis_Null on reddit:

Fusion does not give us limitless energy. It gives us a way to release energy from a very abundent fuel source.

It still takes expensive facilities, and people, performing constant operation and maintenance, to produce a limited amount of power at each power station. And this power still has to be delivered using a network of wires and substations that also have limitations and also need maintenance.

Nuclear Fission Reactors, many of which which have been operating for over four decades now, do the exact same thing. Average price of electricity is ~$0.10/KWH, of which 1-3 cents is profit. Of the $0.08/KWH in cost and operations, about 1-2 cents go towards the actual fuel cost.

Considering how much more difficult fusion is than fission, it seems reasonable to assume that a fusion plant's operation will not be cheaper than a fission plant's operation for similar levels of power generation.

So if we are generous and assume the costs are all the same, minus the cost of fuel, then Fusion power will cost $0.08 cents per kilowatt-hour.

Think of the world-changing possibilities with prices like that!

Oh, actually there really aren't many. Space travel may get denser fuel for ships large enough to warrant a fusion-reactor. And proliferation won't be an issue so the technology can probably be shared and implemented more freely.

But no, we don't magically get an Iron-man Super Power Source that lets us air-condition the outdoors and turn Lead into Gold just for the h*ll of it.

At least no more than we already have with fission power. Fusion will only give us so much energy as we can build power plants, and staff them with technicians, and maintain them all, to produce it.

Which is why I find people obsessing over Fusion - as though it will solve all of our problems - perplexing to say the least. It's a power source with more abundant fuel. It doesn't radically changed the economics of what power sources are, or what we can feasibly do with them. If Fusion is imagined to be so great, we should be pushing for fission, which is almost nearly as great, and has already existed for half a century and powers a fifth of the US grid.

But somehow nobody goes after that.


Fusion removes one bottleneck - the fuel bottleneck. But since fuel isn't currently even close to providing a bottleneck for fission, if a scale-able Fusion plant was delivered to the world today, it wouldn't change much of anything. Materials, skilled labor, and economic demand would keep Fusion behaving pretty much the same way Fission does now.


... Fusion reactors aren't going to be utterly without radioactivity either. Depending on what kind of fusion and what materials they use in construction, the activated products might be shorter lived or less dangerous, but when dealing with nuclear products, it's more a question of proportion than absolute amounts.

From /u/kirime on reddit 5/2017:

Not cheap and certainly not that clean, at least in the foreseeable future. The only things in which fusion is undeniably better than fission is safety and abundance of potential fuel.

The main problem is that deuterium-tritium fusion produces a huge amount of fast neutrons, ~hundred times more than fission for the same power, and those neutrons make the insides of a reactor highly radioactive and greatly reduce the lifespan of any equipment and materials inside the vacuum chamber. Also, tritium itself is radioactive.

So, even if DT fusion is cleaner than typical fission, it still uses radioactive fuel and produces tons upon tons of radioactive waste. Aneutronic reactions exist, but their energy requirements are several orders of magnitude higher than those of DT and they often use more exotic fuels.

And fusion certainly won't instantly make energy free. The cost of nuclear fuel is just a few percent of the total cost of fission energy, the rest is equipment and construction cost. Fusion reactors are far, far more complex and expensive than fission ones, and their fuel isn't free either. Unless the prices will go down much further than expected, thermonuclear energy is going to be more expensive than nuclear, not otherwise.
From /u/edemdee on reddit 5/2017:

Yes you're correct, fusion produces many energetic neutrons which decrease the lifetime of reactors compared to fission reactors. However the materials are radioactive for SIGNIFICANTLY less time than fission. We're talking 50-100 years for fusion while ~1000 years for fission. Not to mention fission reactor produce waste instead so you're actively creating more radioactive material while fusion has no radioactive waste by product. So I would say that this isn't necessarily the MAIN problem with fusion.

Okay yes tritium is radioactive. But, compared to plutonium/uranium for fission, tritium is nothing. Tritium is much more difficult to weaponize and much less radioactive. I think saying that both have radioactive fuel and radioactive waste so they're equally bad is pretty misleading.

Last, there's really no way to tell how much a commercial power plant would cost because we're nowhere near building one. Yes, as I mention elsewhere, ITER, the biggest reactor being built, has astronomical costs but it's also being built on cutting-edge science and being somewhat mismanaged. The cost of building cookie-cutter reactors once the science is all figured out will be much less. Less expensive than fission reactors? I'm not sure, I don't think anyone knows for sure. So it's a little pessimistic to dismiss fusion as definitely being more expensive than fission. That's like saying the car will be more expensive than the carriage and isn't viable when we haven't even gotten the model T yet.

While you raise good criticisms of the field, they're hardly deal breakers in my opinion.
Re: "building cookie-cutter reactors": we've been using fission reactors for 60 years and still haven't managed to do this for them.

From /u/jjs2424 on reddit 5/2017:

> ... how will we USE all of this energy ?
> Will we just use it like we do a fission reactor,
> using the excess heat to generate steam ? ... Or, is
> there some way to use the plasma to generate electricity ...

There are two basic answers, but things are much more complicated for a fusion reactor.

1- Use heat generated by the reaction to generate steam or another hot fluid.

2- Extract energy from the reaction in the form of electromagnetic energy (light, x-rays).

The problem with no. 1 in magnetically-confined fusion is getting the heat from inside the reactor to outside the reactor. This is easy in fission reactors (just circulate a coolant that absorbs energy from neutrons through the reactor).

In magnetically-confined fusion, the reaction requires generating a plasma in a vacuum vessel, so exposing coolants directly to the reaction is out. You could heat up the reactor walls with neutrons, but all solid materials we know of would be physically damaged by highly energetic neutrons and/or become radioactive through neutron activation.

For now the best solution to that problem is to use liquid metal walls (like liquid lithium) inside the reactor to capture the neutrons. This liquid metal would need to flow continuously. Making this work is tricky.

Number 2 is possible if you switch to fusion reactions which do not produce significant quantities of neutrons and instead release most of the energy in the form of photons. Problem is that all the candidate "aneutronic" fusion reactions require much better heating and confinement of the plasma when compared to deuterium and deuterium-tritium fusion, and we still haven't cracked those two reactions.

From /u/Wendelstein7-X on reddit 2/2016:

> When do you think fusion power
> will become a reliable source of energy?

According to the EFDA Roadmap it is planned that the demonstration reactor DEMO should produce first electricity 2050 (as usual: if everything works as expected). It will just be a prototype. After this one can start producing reactors on a large scale. So, the time when fusion power will become a reliable source of energy then depends how fast further reactors can be build. But roughly I would say, not before 2060.


Fusion reactors will always be big devices, so you will unfortunately probably never see a Mr. Fusion for your car. The reason is that a fusing plasma loses energy through its surface area (residual contact with the walls) and produces energy through in its volume. The larger your device, the better the ratio of volume to surface is, just like penguins are larger near the poles than the equator to compensate for the higher heat loss there.


[Re: using fusion reactor as a source of helium:]
The amount of fuel fusion consumes, and hence the amount of helium produced, is very small. The helium we produce will be used in the reactor.

From someone on reddit 3/2016:

[Compared to thorium fission,] two of the big unsolved problems with fusion power are tritium contamination and the creation of a fairly large variety of heavy, long half-life isotopes because of the extremely high energy neutrons flying off the fusion reaction. Even though there is almost definitely less radioactive material being produced in a mass/volume sense, the radioactive material is much more chemically diverse and thus harder to separate out and store safely.

So it's still to be seen which is safer. Neither technology will see the light of day before 2050 anyway, so it's still well up in the air. A lot of it depends on implementation details, not fundamentally the process itself.

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