Talk:High-temperature gas-cooled reactor

Outlet Temperature
I changed "of 1000C" to "up to 1000C". My understanding (from discussions with my Professors) is that they've basically given up on getting 1000C and are shooting for more like 900. I'll try to find a reference. wagsbags 13:23, 21 August 2007 (UTC)


 * The issue is that in order to achieve 1000C average temperature, you'd need zones in the reactor with significantly higher temperatures. If, and that is a HUGE "if", we can recreate the German Triso particle quality, the maximum local core temperature is limited to 1200°C. Both current HTR designs (PBMR, which will is IMHO snakeoil, and the Chinese HTR) are skirting that limit, and their average outlet temperatures are around 850°C. There is nothing you can do about it.


 * Once you start designing an HTR reactor, the average outlet temperature starts to drop. I usually assess the progress of such paper reactors by checking their average outlet temperature... —Preceding unsigned comment added by 129.69.25.217 (talk) 18:48, 31 January 2008 (UTC)

Graphite moderation
Wasn't Chernobil of similar construction and wasn't that one of the design flaws which eventually led to Chernobyl Disaster? I mean, Helium is lighter then air. Loss of pressure in containment vessel would allow intake of air and burning of graphite, releasing radionuclides into atmosphere. —Preceding unsigned comment added by 147.91.1.41 (talk) 10:20, 25 October 2007 (UTC)


 * No. This reactor has absolutely NOTHING to do with RBMK reactors of Russia. Reactivity excursions are physically impossible with HTRs. And air and water ingress are some of the standard accident analysis necessary for these reactors. Both are fairly harmless to the reactor since the core consists of trillions of micro containments made from silicon carbide: The fuel particle.
 * Air and water does not react with the SiC barrier at these temperatures and doesn't degrade these fuel particles. Additionally, the core itself is very, very weakly radioactive. If all graphite within the reactor were to be pulverised and spread throughout the HTR building, the maximum occupational radiation exposure within that building would be 0.14mRem/year. That's another word for fuckall. —Preceding unsigned comment added by 129.69.25.217 (talk) 18:57, 31 January 2008 (UTC)


 * AFAIK, it was the combination of graphite moderator and water coolant which made the RBMK a death trap. Most British reactors are graphite-moderated, but use CO2 coolant (see Magnox and Advanced gas-cooled reactor). --GCarty (talk) 17:14, 9 June 2008 (UTC)


 * The AGCR, the HTGR, and other reactors like this are gas-cooled but graphite moderated. Helium or nitrogen or carbon dioxide doesn't act as a moderator. Chernobyl had a graphite moderator and water coolant. The water acted as a moderator, too. So when the water boiled off, moderation was lost, and things became dicey. If the helium is lost from an HTGR, there's a decrease in heat transfer efficiency, but it's nothing that needs to be immediately worried about, at least beyond the plant. Smaller HTGRs (10 - 150 MW or so) with steel reactor shells, graphite particle fuel (prismatic/pebble bed) and convective vessel cooling often can just be walked away from in the event of a loss of coolant as the natural convective action of the air flowing over the shell will carry away the decay heat. For larger reactors, within a few days from the complete, limiting depressurization fault, some other form of cooling should be provided to prevent an outgassing of particles due to the decay heat. But even if no one did anything, there would only be a small radioactive release. British AGCRs use metal fuel, so there are some more modalities with that than with standard HTGRs. Katana0182 (talk) 15:06, 20 November 2009 (UTC)

Suggest move to High Temperature Gas Cooled Reactor
I suggest this page be moved to 'High Temperature Gas Cooled Reactor'. INL in the US is no longer referring to the NGNP project reactor as a VHTR, but rather as a HTGR.Katana0182 (talk) 20:40, 28 March 2010 (UTC)

I'm fine with moving it, but I think perhaps 'High Temperature Reactor' might be better since it is more inclusive, i.e. the AHTR and liquid salt cooled design variants could also be discussed under HTR and I think they fit in since they are 'proposed' to use a lot of the same technology. It might also be prudent to mention the names historically used along with varius experiments and experimental programs that could be included, i.e. PBMR, Gtmhr, HTTR, AHTR, VHTR, HTR-10 etc... That being said, I think VHTR has been used enough in the past to at least warrant a mention. I am not sure though that the proposed NGNP design is settled enough yet to make many assumptions, and until they actually reach criticality, will continue to view it as a paper exercise. I of course am not volunteering to do this work, so take my recommendation as you please, and if you decide to rename it, please put in a wiki rediriect from the names of the original constituent articles. Lcolson (talk) 18:32, 30 March 2010 (UTC)


 * I agree with the idea of a major reorganization. I think HTGR is the most common name/concept, and most of the information here can and should be moved to a HTGR page.  However, VHTR should also have its own page.  Although VHTR is essentially a type of HTR, VHTR is specific to the GenIV reactor forum.  In my opinion, the VHTR name is tied to a design capable of especially high temperatures and/or the thermal-chemical sulfur-iodide hydrogen production.


 * I also like Lcolson's idea of creating a HTR page. Perhaps information on liquid salt variety can be put there, and contrasted with HTGRs.  Or perhaps it can stay on the VHTR page.  Ajnosek (talk) 03:50, 12 July 2011 (UTC)

OK, so the Move probably explains why we now have Very High Temperature Reactor redirecting to this article that now doesn't clearly explain the concept or differences. Is VHTR still used ? Has its meaning changed (gas cooled or not, temperature target) ? - Rod57 (talk) 21:08, 9 October 2021 (UTC)
 * This article was moved from 'Very-high-temperature reactor' to 'High-temperature gas reactor' in May 2021 by User:Jadebenn with comment 'Article only talks about HTGRs'. Here  As it happens, I agree with the move.   Molten salt and gas cooled reactors are sufficiently different things as to deserve their own pages.  Indeed, we have a molten salt reactor page. But the article *did* (and does) contain material on molten salt reactors.  I am simply going to remove the molten salt reactor material to keep the content in line with the title. - Crosbie 02:48, 10 October 2023 (UTC)
 * For what it's worth, VHTR is more of a classification of reactor than type. I moved the article because (at least at the time), it only talked about HTGRs and so felt misnamed. VHTR might deserve its own article, as it's a more umbrella term for any reactor design producing a sufficiently hot output temperature (of which HTGRs are one of the more common designs). – Jadebenn (talk &middot;&#32;contribs &middot;&#32;subpages) 03:55, 10 October 2023 (UTC)

High Temperature vs. Very High Temperature
My field is Electronic Engineering so I am not really an expert. My understanding is that there is a distinction between a HTGR such as the prototype built at Fort Saint Vrain Colorado that used steam generators and steam turbines (Rankine cycle) for power generation and a VHTGR such as the new proposal from General Atomics that use the gas coolant directly to drive a gas turbine (Brayton cycle). Combined cycle would also be possible for the VHTGR. Tyrerj (talk) 15:19, 9 December 2011 (UTC)

Breeder reactor
Can this (very high temperature reactor) be used as a breeder reactor? — Preceding unsigned comment added by 70.241.21.7 (talk) 20:51, 23 March 2012 (UTC)

Why is AGR not a HTGR?
Outlet temperatures in the table are as low as 700C. The UK's CO2 AGR fleet has outlet temperatures of 640C. That's lower, but not that much, and its still double that of a typical water-cooled design. The lede states that VHTGRs are 750 and up, so it would seem (assuming that's accurate) that HTGRs overlap and have some lower lower bound. So what is the definition that makes one a HTGR and the other a M(medium)TGR? Maury Markowitz (talk) Maury Markowitz (talk) 12:29, 12 December 2023 (UTC)