Talk:Traveling wave reactor

NPOV dispute - History

I feel that selected language in the "History" section does not meet Wikipedia's Neutral Point of View (NPOV) guidelines.

Specifically the bolded selections in the following:

• In 2010 a group from Terra Power applies for the patent EP 2324480 A1 following WO2010019199A1 "Heat pipe nuclear fission deflagration wave reactor cooling" where in order to be accepted calls the traveling or singular wave "deflagration" as it is moving with about 1-4 inch per year, and introduces the heat pipe cooling already applied in space reactors built at LANL and INL since 2000, or even earlier, using the flaws and weaknesses of USPTO.

While the debate about the strengths and weaknesses of the USPTO is certainly a subject that deserves discussing (perhaps on the USPTO's Wikipedia page!), I do not feel that this page is an appropriate venue for that topic. If the original editor feels that Terra Power exploited a loophole in the USPTO that allowed them to file for a patent on something without meeting the accepted prerequisites for a legitimate patent filing, the language here does not read as being neutral regarding this subject. I suggest changing the paragraph to something such as:

• In 2010 a group from Terra Power applied for US patent EP 2324480 A1 following WO2010019199A1 - "Heat pipe nuclear fission deflagration wave reactor cooling". This patent filing uses the term "deflagration" to refer to a traveling wave or singular wave that moves approximately 1-4 inches per year, and introduces a heat pipe cooling system strongly resembling one already applied in space reactors built at LANL and INL since 2000 or earlier. This patent filing is potentially controversial as it could be seen as a form of "patent trolling" or causing a "chilling effect" on further research into this technology, as the patent could prevent development of similar technology by competing organizations. The patent was technically filed to cover the design of the cooling system, but the inclusion of the reactor technolgy in the filing, despite not actually existing in a demonstrable real-world form, gives the patent owners a potential degree of patent coverage of the reactor technology as a whole. No legal challenges or court rulings currently exist on this patent filing.

Various talk posts below state that the company is a patent troll, and that patents such as the above one could have a chilling effect on future development of Breeder Reactor work/patents, however the language regarding this needs to remain neutral, and should include citations to credible sources such as scientists, journalists, or lawyers who have publicly stated/discussed concerns regarding patent filings such as this and their effect on the industry. Even then, any additional language should strive for neutrality, and not take a stance on the legitimacy or morality of such patents. While nobody doubts the existence of patent trolls, and there is much discussion to be had regarding the strengths and weaknesses of the USPTO, this is not an appropriate place to have such a discussion.

Further language could be added to elaborate on the patent filing and its potential effects on subsequent research in this field, however it may potentially need its own heading at that point to clarify that this was a subject of controversy. The language should cite references to credible sources (news articles, trade publications, scientific journals, etc) that indicate the patent was created in the monetary interest of certain individuals/organizations, not for the purpose of protecting research but for the purpose of imposing licensing fees on future uses of this technology, and the language should attempt to show clear and credible evidence (through citations) that the patent filers do not intend to further develop the technology, only to sit on the patent until someone else develops this technology.

If you have questions on Wikipedia's NPOV policy, please read over https://en.wikipedia.org/wiki/Wikipedia:Neutral_point_of_view for clarification of Wikipedia's Neutral Point of View policy.

Illuminerdi (talk) 14:06, 4 September 2014 (UTC)Illuminerdi

Good catch. I think you make a legitimate point here. I would go further, and say that the language about the cooling system resembling something else, and the language about the patent being potentially controversial should be removed until and unless there is a reference for it. In other words, remove it now and add it back in when & if an editor adds the language and the reference at the same time. In fact, does the potential controversy of Terra Power belong here at all? Terra Power's research, publicity (which is greater than a single TED talk), and activities (particularly in Asia) do have bearing on the history of the concept, but this controversy (if it exists) might be better placed in the article about the company or it's parent company. That is, until & unless a good reference can show that the controversy (if it exists) has impacted this history of this concept. James Cage (talk) 15:19, 4 September 2014 (UTC)

Removed the offending passage, as the patent has been withdrawn. Lfstevens (talk) 20:23, 14 October 2015 (UTC)

Notability

Please expand/rewrite this stub. I would expect much public interest in the topic in the coming weeks. Traveling wave nuclear reactors were presented to the American Nuclear Society this year, and they were in the news last week (see my references). The concept is not new, but I found no Wikipedia entry mentioning them. It could be made a subsection of Breeder_reactor. I'm no expert on nuclear, so someone else will need to write the entry. Thanks. DuBois (talk) 01:38, 20 August 2008 (UTC)

This article is based on rather promotional and speculative theoretical discussions and a "preliminary design" of a reactor by a commercial entity that has never been constructed or tested. The "technology" is not a technology because it doesn't exist, and has all the credibility of cold fusion research at Utah universities of a few years ago. It is unclear that this is sufficiently notable to warrant an article in Wikipedia. Mervyn Emrys (talk) 01:59, 27 February 2009 (UTC)

Its theoretical existence and publication before a working prototype has been developed may be a means of extorting license fees rather than actually furthering the state of the art. The company carrying the patent has been described as a patent troll. As such, although the invention may not work in reality, it may work as a chilling effect on breeder reactors.Kgrr (talk) 16:50, 6 March 2009 (UTC)

Hi folks. This reactor was featured in the September 2009 edition of Nuclear News, the trade magazine of the American Nuclear Society. It's generating lots of buzz, so there's a new version of this page up now. Check it out. Ntouran (talk) 01:32, 22 October 2009 (UTC)

Gravity waves

"The traveling wave reactor is proposed for the generation of gravitational waves with nuclear reactions" I don't believe that the TWR and the apparatus described in this article have anything in common except for their name. I going to be bold and will remove it from the article.

Here is what I cut: The traveling wave reactor is proposed for the generation of [[gravitational wave]]s with nuclear reactions<ref>[http://www.drrobertbaker.com/docs/AIP;%20HFGW%20Nuclear%20Generator.pdf Generation of Gravitational Waves with Nuclear Reactions]</ref>.

Kgrr (talk) 16:41, 6 March 2009 (UTC)

Press Release?

IMO, the majority of this article reads more like a press release from Intellectual Ventures than an encyclopedia articles, particularly the following:

... These problems are mostly accepted as a given, but not by a group of researcher­s at Intellectual Ventures, an invention and investment company in Bellevue, WA. The scientists there have come up with a preliminary design for a reactor that requires only a small amount of enriched fuel--that is, the kind whose atoms can easily be split in a chain reaction. And while government researchers intermittently bring out new reactor designs, the traveling-wave reactor is noteworthy for having come from something that barely exists in the nuclear industry: a privately funded research company.

As it runs, the core in a traveling-­wave reactor gradually converts nonfissile material into the fuel it needs. Nuclear reactors based on such designs "theoretically could run for a couple of hundred years" without refueling, says John G­illeland, manager of nuclear programs at Intellectual Ventures.

Wave of the future: Unlike today’s reactors, a traveling-wave reactor requires very little enriched uranium, reducing the risk of weapons proliferation ...

--68.115.172.154 (talk) 14:16, 25 June 2009 (UTC)

Those four paragraphs were copied verbatim from the Technology Review article linked to in the references section. I've reverted them accordingly. — Xaonon (Talk) 17:50, 30 June 2009 (UTC)

The "Conceptual Design" paragraph reads still like an advertisement for TerraPower! TerraPower is in an ongoing process to design TWRs that improves on present-day reactor technology while keeping them safe, affordable, and sustainable as a long-term clean-energy power source. —Preceding unsigned comment added by 87.145.3.110 (talk) 21:15, 5 January 2011 (UTC)

Nuclear reactions

The article is lacking any hint on what the reactions and material would be that would provide the fission process. Plutonium 239? How could it be processed _inside_ the reactor with enough purity to enable the continuation of fission? Looks like a science fake to me. --Edoe (talk) 08:56, 11 September 2009 (UTC)

It burns plutonium 239, produced by bombarding uranium 238 with neutrons from enough uranium 235 to make enough P-239 to sustain the reaction on its own. It seems theoretically possible; that it was first introduced in 1958 and hasn't been pursued seriously until now makes me think it has difficulties in realization that haven't been overcome.RussellBell (talk) 03:26, 27 June 2010 (UTC)

Not a science fake, though the details in this article are a bit thin. I'll provide some nuclear fuel cycle details and an experienced editor can put them into proper Wiki format for me if you wish.

0.7% of natural uranium metal is "fissile" uranium-235, which today fuels most of the world's nuclear reactors.

99.3% of natural uranium metal is uranium-238, which does not easily fission and cannot sustain a nuclear chain reaction. However, when U238 captures a neutron it undergoes two radioactive decays and transmutes into plutonium-239, which is easily fissioned by neutrons of any energy. In this sense Pu239 is called a "fissile" isotope (can sustain a nuclear chain reaction) while U238 is a "fertile" isotope (cannot sustain a nuclear chain reaction but can be used to breed a fissile isotope in the presence of neutrons).

When a nucleus of plutonium-239 or uranium-235 fissions, it typically releases two fission fragments and 2 or 3 neutrons. On average, U235 releases about 2.4 neutrons per fission, while Pu239 releases on average about 2.8 neutrons per fission IF the fission is triggered by "fast" (energetic or un-moderated) neutrons. Since a stable fission chain reaction is sustained when each fission event releases neutrons that lead on average to 1.000 successive fission events, there are 1.4 neutrons left over in a typical U235 reaction or 1.8 neutrons left over in a "fast neutron" Pu239 reaction. In a conventional water-moderated reactor, most of these excess neutrons are absorbed by hydrogen in the water, or diffuse ("leak") out of the reactor core and are lost. In a breeder reactor, of which the Traveling Wave Reactor (TWR) is one specific type, there is typically little or no moderator, so a large fraction of fissions take place with "fast" neutrons, increasing the average neutron yield per fission and reducing the number of neutrons absorbed/lost. It is possible then in certain fuel geometries, that for each Pu239 fission on average 1.0 neutrons are used to sustain the stable chain reaction, more than 1.0 neutrons are captured by U238 to form new Pu239 nuclei, and less than 0.8 neutrons are absorbed or lost. In this sense any breeder reactor, including a TWR, "creates more fuel than it consumes" because it turns a non-fissile isotope (U238) into a fissile isotope Pu239. There is no "perpetual motion machine" here, the fuel is U238, which must be periodically re-supplied, then transmuted by neutrons into Pu239, then consumed by fission. Conventional reactors cannot run on U238 alone, because too many neutrons are absorbed in the water to breed as much fuel as the reaction consumes. Most conventional reactors use fuel that consists of about 3% fissile U235 and 97% fertile U238. Conventional reactors consume most of their U235 and convert a small fraction (typically 1% to 2%) of the U238 to Pu239; then the fuel is considered "spent" because the accumulating fission fragments begin to absorb too many neutrons to continue the chain reaction. A TWR, or any breeder reactor, can run much longer than a conventional (water-moderated) reactor, and can produce much more energy from the same mass of nuclear fuel, because a much larger fraction of the U238 is converted to Pu239 and fissioned in a breeder reactor before the accumulated fission fragments build up to the point where the fuel must be removed from the core. This is especially true if the "spent" fuel is reprocessed to remove the neutron-absorbing fission fragments, and then reformulated into a mixture of the bred Pu239 mixed with the un-transmuted U238 and some fresh U238 to make up the balance. Since a breeder reactor produces more Pu239 than it consumes, in principle such a reactor can run for its entire life on U238, a very inexpensive and abundant material compared with the conventional fuel enriched in fissile U235 that most reactors use today. (Remember natural ore has 99.3% U238 and only 0.7% U235). Reprocessing the "spent" fuel and putting it back into the reactor would also obviously greatly reduce the volume of radioactive fuel waste left over for disposal. In this sense a breeder reactor with fuel reprocessing can "eat its own waste"--but not entirely-- there is always the small fraction of the fuel mass in fission fragments that get kicked out of the cycle during each reprocessing step. Some of these fission fragment isotopes are highly radioactive-- some are dangerous-- some are extremely valuable for medical and scientific research even though they are dangerous. It is not clear whether they will ultimately be considered "waste" or "valuable industrial radioisotopes." This depends largely on how they are handled during reprocessing and whether there is sufficient commercial market to justify the expensive purification processes needed to separate them.Kenricci (talk) 08:14, 9 March 2011 (UTC)

One inserted correction: The exess neutrons in a light water reactor are NOT absorbed by the water, some isut enough are absorbed by U238 to produce Plutonium which (usually) produce more than half te energy close to emoval of the fuel element. Usually when "burnt out" there is a little more Plutonium than U235! Heawy water reactors consume less neutrons and can thus use fuel with lower enrichment, BUT are often less stable then light water reactors. (In Sweden one small reactor was closed down when better stability computations became avaible (Ågesta) and one was never compleated (Marviken)Seniorsag (talk) 12:55, 7 September 2016 (UTC)

As pictured, the zone where fission occurs seems very thin. I don't understand why it isn't losing too many neutrons into the already-burnt zone to continue the chain reaction.

Kirk Sorensen has a discussion of spent fuel, and the potential value it contains: http://energyfromthorium.com/2011/01/05/is-nuclear-waste-really-waste/

—WWoods (talk) 21:18, 9 March 2011 (UTC)

This is what Bill Gates invested in...

Right? 99.32.60.170 (talk) 21:22, 17 February 2010 (UTC)

The company that started this project, Intellectual Ventures, is Nathan Myhrvold's, the former chief technology officer at Microsoft and the person Bill Gates identified as the smartest man he ever met.RussellBell (talk) 03:26, 27 June 2010 (UTC)

Speculative Technology

See the following for the first Wikipedia entry on the PS3: http://en.wikipedia.org/w/index.php?title=PlayStation_3&oldid=276259

The Traveling Wave Reactor technology (and the current Wikipedia page about it) is much less speculative... And Traveling Wave is a possible solution to the world's climate and energy problems, so it is certainly more worthy of discussion than an entertainment system. (Oh, and there even is a direct quote from Sony's Marketing) --157.161.33.81 (talk) 11:34, 20 February 2010 (UTC)

Problems, Waste

The nature and quantity of the waste material remaining ought to be discussed in more detail. This is a major advantage of this type of design over traditional nuclear plants, but there is still nuclear waste produced. Its nature and quantities and how it would be handled need to be discussed.

Nuclear power with minimal waste and no nuclear proliferation issues? Lower fuel costs? Safer? This plant promises to solve most of the major problems plaguing nuclear power. So what are the problems in moving this from the drawing boards to construction? Do new materials need to be developed? Processes that remain uncertain? What remains to be done? —Preceding unsigned comment added by R Stillwater (talk • contribs) 07:00, 21 February 2010 (UTC)

Agreed. Without a discussion of the waste products and management of these, this is a silly article. Hermanoere (talk) 16:06, 25 September 2013 (UTC)

Controlling the Reaction Rate

How is the rate of the reaction controlled once it is started? Does it have to burn until the fuel is exhausted, e.g. over several decades? How can the reaction rate be slowed down or stopped? Can it be speeded up? (Thanks to friend RLP for posing these questions) Lbeaumont (talk) —Preceding undated comment added 13:31, 25 February 2010 (UTC).

Allegedly this design moves fuel between zones, rather than arranges it in the first place so that it burns continuously without manipulation for its entire life (the 'candle' model). If so, then they can manipulate the fuel in such a way as to control its rate of burn. Doubtless they have to have some way to stop the reaction in case of earthquake or a riotous mob taking over the facility... which they could do by flooding it with neutron absorbers.RussellBell (talk) 03:26, 27 June 2010 (UTC)

Why does it progress at such a slow rate in the first place? Cesiumfrog (talk) 12:46, 29 April 2010 (UTC)

The reaction requires 'ignition': the conversion of U-238 to P-239 by neutrons provided by enriched uranium. I imagine they could do this quickly but it's probably cheaper and safer to do it slowly.RussellBell (talk) 03:26, 27 June 2010 (UTC)

Re-using their own fuel

At the end of the article is a sentence: "TWRs are also capable, in principle, of reusing their own fuel. The used metal fuel from TWRs will still contain a high fissile content. Recast and reclad into new driver pellets without separations, this recycled fuel could be used to start fission in additional TWRs, thus displacing the need to enrich uranium altogether."

Can someone expand on this? This sounds suspicious, kinda like perpetual motion or something that's in violation of one law of physics. 208.38.1.1 (talk) 19:08, 25 February 2010 (UTC)

Only had a quick scan through the article but I think that the reactor wouldn't be able to burn all the fuel it produces (probably P 239 or something like that) so you end up with a mixture of waste and fuel (with the fuel probably only making up a small amount if the reactor does anything like what it say it does). So you reprocess the stuff and remove the waste ending up with much less metal than you started with but some thing that could be used as one of these driver pellets and therefore don't need to add enriched uranium only more depleted uranium. However this does raise the question of how can the power plant not burn this fuel and still burn depleted U as it doesn't leave much room to maneuver unless they have some tech up their sleeve we don't know about —Preceding unsigned comment added by 212.9.109.152 (talk) 23:49, 22 March 2010 (UTC)

Uranium is about 99.3% 238, .7% 235. Bombs and other nuclear power plants use U-235, enriched to about 90% for bombs, 4% for power plants. U-238 can capture a neutron (produced by starting with enough U-235) then decay into Plutonium, P-239, which is also usable for bombs and power. Breeder reactors already do this but require stopping the reaction, taking out the P-239, and processing it. The advantage of the TWR (if it really works) is that it burns the P-239 it produces in place, which would be a huge advantage over 'regular' breeder reactors. I would think that this would mean that it shouldn't leave any uranium or plutonium behind, except a little at the end of its life when there's too little to sustain a reaction. But the information we have is short on details.RussellBell (talk) 03:26, 27 June 2010 (UTC)

See my comment above under "nuclear reactions" concerning the form of the waste. Originally, the TWR concept was intended to leave the fuel fixed in place, while a "fission burn wave" slowly moved through the fuel. Edward Teller was particularly fond of this model, because it was inspired by his work on the hydrogen bomb. He wanted to design a reactor that worked like an ultra-slow-motion fission bomb, consuming the nuclear fuel in 100 years instead of in 10 microseconds. Several of Teller's papers, including his last paper published posthumously in 2005, extol this idea. Unfortunately, there is no known geometry that confines the neutron flux well enough to make this concept feasible. The recent admission by the TerraPower group that they decided "to move fuel through the burn wave instead of having the burn wave move through the fuel" is an implicit acknowledgment that they have not found a true TWR solution. The solution they have chosen is more accurately called a "breed-and-burn" reactor core design, a type of breeder reactor that can sustain its reactivity by U238 refueling and by fuel shuffling without fuel reprocessing--although of course most nuclear engineers would acknowledge that even if you CAN run your breeder reactor without ever reprocessing the waste, that does not mean you SHOULD. Rather, the TWR group has also acknowledged recently that they believe their fuel cycle should be closed by a fuel reprocessing step, since the first pass through the "burn wave" will not actually consume more than about 10% or 20% of the U238 in the fuel. Sorry my comments here are missing references. If you are interested enough to reply to this, I'll add some later.Kenricci (talk) 08:35, 9 March 2011 (UTC)

It would be good if the "Travelling wave vs. standing wave" section were changed to a discussion of "Reactor core configurations". It currently seems to be a fragment of an argument that's not presented anywhere in the article. It would be great to have some numbers for percentage of potential fuel that's activated, percentage of fuel burnup, percentage of waste products burnup, and mass of residual fuel and waste per unit of electricity generated. Densely (talk) 18:49, 7 December 2011 (UTC)

speed of reaction a potential neutron bomb ?

There is something i wonder here, it should work with used fuel rods. Those left overs where never designed, to be chemically in some kind of balance. So their makeup of uranium and plutonium, is rather something statistic balance, but never mentioned to be a perfect mix. Now what would happen if such a device would use a non perfect mix. Will the traveling wave, dimm like a candle burning out. Or instead could it suddenly flame like a neutron bomb ? Dont get me wrong if this idea works it could be nice, but i wonder how safe it really is. —Preceding unsigned comment added by 84.107.161.119 (talk) 13:54, 22 March 2011 (UTC)

This reactor, just as any reactor, will need to control its reactivity. Typical light water reactors will need to enrich the U-235 to 5%, which is more than enough positive reactivity to reach criticality, because they will lose U-235 as they operate. To compensate for the extra reactivity, the reactor will need negative reactivity to operate at the desired power level. Typically this is done with control rods or burnable poisons. The TWR however is a breeder reactor, which means that it produces more fuel than it burns. So you are right that as the reactor operates, the changing composition of the fuel will add reactivity. However, changing the composition of a reactor is a extremely slow process, especially compared to let's say, the added reactivity of pulling a control rod out. In addition, such a reactivity addition (in properly designed reactor) will lower reactor power in a mechanism known as a negative reactivity feedback. In order words, the changing composition of the reactor core will not create an uncontrolled reactivity excursion, but nevertheless, just as any reactor, the total reactor reactivity should be designed as to not allow large positive reactivity events. Ajnosek (talk) 02:20, 6 December 2011 (UTC)

Blow-up modes

The preprint of the paper by Rusov et al. (see external links section) says (see p. 41 for a summary) that the TWR wave can experience blowup (no wiki article about this kind of blowup it seems). 86.127.138.234 (talk) 22:40, 28 January 2015 (UTC)

Quoting from the abstract of the Rusov paper, "Some variants of the possible stability loss due to the so-called blow-up modes (anomalous nuclear fuel temperature and neutron flow evolution) are discussed and are found to possibly become a reason for a trivial violation of the traveling wave reactor internal safety."MartinTheK (talk) 22:58, 30 November 2015 (UTC)

References

Define LWR

Someone used the acronym LWR, but failed to define it initially. Please do so. - KitchM (talk) 18:45, 18 February 2016 (UTC)

What? - KitchM (talk) 18:39, 7 September 2016 (UTC)

LWR = Light Water Reactor, meaning liquid water is used to both cool the reactor and moderate the speed at which neutrons move through the core. https://en.wikipedia.org/wiki/Light-water_reactor — Preceding unsigned comment added by 73.11.101.117 (talk) 16:06, 2 November 2016 (UTC)

Where does the "travelling wave" distinction come from?

In the overly simplified "burn like a candle from one end to the other" model, burning starts at one end of the pile of fertile fuel, forms fissile material, burns fissile material, leaves fission product behind, and eventually gets to the other end. I see the red/green/black/blue graphic (copied below) portraying much the same model but as a "candle" burning from the inside out.

As explained further along in the article: [Only for Terrapower's design(?)] That is not quite right. Fuel rods will be frequently shuffled around to keep the various radiation densities more uniform throughout the core.

So now instead of a cylindrical shell of fission activity with a gradually increasing mean radius, the various shaded green squares will be frequently shuffled around, evening out the instantaneous distribution of color and bringing to (my) mind the question "What wave?".

Same question from a different initial direction: What exactly distinguishes a TWR from any other breed/burn reactor with operators hyperactively shuffling its rods?

This is the animated gif I refer to. I copy it here in case it is removed from the article before someone reads this comment.

Numeric simulation of a TWR. Red: uranium-238, light green: plutonium-239, black: fission products. Intensity of blue color between the tiles indicates neutron density

https://commons.wikimedia.org/wiki/File:Laufwellenreaktor.gif#/media/File:Laufwellenreaktor.gif

Why liquid metal?

What about liquid metal suggests it as the better/best coolant for this reactor?

Or is liquid metal even the best candidate? — Preceding unsigned comment added by 2601:1C2:1201:7860:10A4:665A:C0DE:9CD7 (talk) 07:56, 8 May 2017 (UTC)

Dubious

Article currently reads in part TWRs differ from other kinds of fast-neutron and breeder reactors in their ability to use fuel efficiently without uranium enrichment or reprocessing.

The animation, on the other hand, starts out showing the sixteen squares in the centre as Plutonium-239. This has presumably been provided by reprocessing. There is no other available source.

And the only ways around this would be to use either U-235 (as HEU) obtained by enrichment, or U-233 obtained by reprocessing fuel from other Thorium reactors. So the Thorium/Uranium fuel cycle, however the reactors are designed, needs fissile material from the Uranium/Plutonium fuel cycle to get started. That's why the (often-repeated) claim that this class of reactor somehow avoids the need for enrichment or reprocessing is quite frankly deceptive.

This has two important implications. One is that if this class of reactor really avoided the need for both reprocessing and enrichment, that would reduce proliferation concerns. But it doesn't. It needs one or the other.

The other thing is, this need of an initial fuel load is a very important limiting factor on the use of Thorium at present. It is why India has a three-stage plan. They hope to switch to Thorium (of which they have lots) in stage 3. But first they need stages 1 and 2 to build up their inventory of fissile material in order to provide the initial fuel loads for the stage 3 reactors.

The travelling wave reactor is not exempt from this need for an initial fuel load, as the animation shows quite clearly. Andrewa (talk) 16:42, 2 September 2020 (UTC)

I agree that the claim is dubious. To start a chain reaction, you need a critical mass of fissile (not just fertile) material. ---Avatar317^(talk) 21:28, 2 September 2020 (UTC)

From what I understand, the reactor is able to produce the material to "initiate" another reactor, so in theory what really is needed is a small amount of fissile material to start an entire nuclear program. There is a huge amount of plutonium in storage around the world. For example, Japan alone has over 10 tons of plutonium. --Ita140188 (talk) 23:53, 2 September 2020 (UTC)

True if the reactor is configured as a breeder, which is possible, but not essential to the concept. However, enriched or reprocessed material is essential. Also true that Japan has a stockpile of Plutonium. But India is still building theirs up, in order to switch to Thorium once this is done. Andrewa (talk) 18:33, 13 March 2022 (UTC)

I understand the same: there is the need for radiactive material only to initiate the reactor. — Preceding unsigned comment added by 186.26.113.114 (talk) 01:31, 15 September 2021 (UTC)

And this is exactly the sort of (very common) lack of understanding that the article currently reflects, and that Wikipedia should address not perpetuate. For a start, U-238 and Th-232 are both radioactive (I assume radiactive is a typo). So radioactive material is needed throughout the operation. Andrewa (talk) 18:33, 13 March 2022 (UTC)

Possible Problems

To get a better picture of the subject, it is worth to read the German version of the article as well. More stuff there, especially "Possible Problems". Btw, do Bill Gates and TerraPower know the German version? 87.185.222.87 (talk) 14:50, 25 February 2021 (UTC)