Talk:Pebble-bed reactor

message: The company in South Africa that is developing the PBR always appear to gloss over the safety concerns in an attempt to minimize them in the eyes of the public.  I personally think this technology is viable, but when playing with nuclear power, one shouldn't ever downplay the risks.  
There is a strong likelihood that this Wikipedia article is being modified by a public relations company, or an expert in PR.   —Preceding unsigned comment added by ObseloV (talk • contribs) 04:57, 21 January 2009 (UTC)
replies: text: I agree that the language is not impartial. The content is informative, however.  I don't know how much traffic will come from today's New York Times story, but I might put up a neutrality dispute sign and see what shakes out. - Cwmagee (talk) 05:22, 25 March 2011 (UTC)
thread_title:  "Written like an advert" 

message: I just tried to access reference 9 but it appears to have 404d...
87.112.74.244 (talk) 11:46, 3 January 2008 (UTC)
thread_title:  Reference 9 is missing 

message: In section Pebble_bed_reactor#Safety_features, it says:
Later problems with the AVR reactor resulted in a small release of radiation to the public.
I really think we need a citation for this event to clarify just how safe or unsafe these reactors are. I would also like to see information on exactly how "small" it was, if that information can be found.
The best reference I found in Googling is at the end of a page on how  pebbles circulate within the reactor, but it is still very vague, and not a very authoritative source. Another potential reference is Reactor Watchdog Project's info page on PBMR, which has more detail, but also comes from a site with an obvious anti-nuclear spin.
It is also mentioned in THTR-300#Decommissioning, but I don't see a citation there either.
Different sources identify the event as happening in 1986, 1988, or May 4, 1985. 
        Correct is May 4, 1986  —Preceding unsigned comment added by 80.137.39.188 (talk) 10:00, 14 October 2010 (UTC)
replies: text: Check Dr. Moormann's paper http://hdl.handle.net/2128/3136 Jrincayc (talk) 13:16, 18 November 2008 (UTC)

text: For the AVR, the best resource is probably "Decommissioning of the AVR Experimental Nuclear Power Plant, Disassembly of Plant Components and Entombment" by Arbeitsgemeinschaft Versuchsreaktor AVR in Nov 1991, available on the NEA cdrom http://www.nea.fr/abs/html/nea-1739.html.  In it it states that the releases off site were less than 1 μSv/a from the exhaust air, 3.5 mSv/a at the edge of the fence when the plant was operating, and 0.42 mSv/a at the edge of the fence at worst when the plant was shutdown (due to some stored radioactive waste). Jrincayc (talk) 04:51, 27 November 2008 (UTC)
replies: text: The initial quotation was incorrect.  The AVR had no problems.  It was the THTR that had the pebble problem.  I would imagine there's a decommissioning white paper on the THTR out there that discusses the incident, but I cannot find anything in English. 70.162.2.55 (talk) 06:36, 3 December 2008 (UTC)
thread_title:  Citation needed on public radiation release 

message: Articles like this give me the impression that potentially, a shaman would need merely mix a powdered mineral containing unenriched uranium with a pure lampblack in order to make an ever-burning fire.  (Though some ill might have befallen some villagers burned with it, he can scarcely be blamed for the judgments of the gods)  Is it plausible for people to have made reactors this way in Neolithic times? Wnt (talk) 22:06, 7 August 2008 (UTC)
replies: text: Rather implausible.  You might be able to do it with natural uranium, but you would need pure uranium, not uranium ore.  See Chicago Pile-1 and Natural nuclear fission reactor Jrincayc (talk) 04:02, 17 November 2008 (UTC)
thread_title:  Neolithic nuclear reactors? 

message: A pile of "spent" pebbles will still get hot, right? It seems like if the issues with cesium and strontium leaking out could be resolved, one could dump them in a sea with circulation issues to circulate the water by heating the depths. 65.46.169.246 (talk) 15:07, 16 March 2011 (UTC)
replies: text: It is unlikely that water cooling will be necessary to cool this type of spent fuel.  Pebbles have relatively low power densities and are designed for high temperatures.  A better idea is to keep them away from possible corrosive environments like saltwater.Ajnosek (talk) 18:18, 19 August 2011 (UTC)
thread_title:  burial at sea to disrupt thermoclines 

message: What are the typical dimensions of the pebbles used in such reactors? This should be included in the text of the Design section, as now it seems one can only roughly deduce their size by looking at one of the pictures. —Centrx→talk • 05:21, 18 November 2008 (UTC)
replies: text: The pebble diameter for the AVR, THTR, HTR-10 as well as for the planned PBMR in South Africa and the planned HTR-PM in China are all 6cm. There is a lot of experience in manufacturing and handling as well as experimental data about the 6cm diameter pebbles due to the AVR and THTR program. There isn't really any benefit to changing this diameter in terms of reactor physics and thermohydraulics, but it would cause a significant amount of work in getting new reactors designed and licensed. --129.69.25.217 (talk) 12:36, 20 January 2009 (UTC)
thread_title:  Dimensions of the pebbles 

message: Section "Safety Features", final paragraph contains the text "The graphite is the moderator for the reactor, and are strong containment vessels", which defies grammar and seems meaningless.  —Preceding unsigned comment added by 212.159.59.5 (talk) 18:33, 27 February 2009 (UTC)
thread_title:  Textual error? 

message: There's a scattering of [citation needed] markers -- any chemists out there who can assist? E.g.:
* in 'Containment', this might be appropriate for "Pyrolytic carbon can burn in air when the reaction is catalyzed by a hydroxyl radical (e.g. from water)". Is there a Chemistry Wikipedia group that could help? ThomasNichols (talk) 11:46, 6 October 2009 (UTC)
thread_title:  Cleaning up citations 

message: Reference 6 returns a 404 error mostly in German.  Some sleuthing may be required to find the correct new link.  —Preceding unsigned comment added by 65.160.229.33 (talk) 17:01, 14 March 2011 (UTC)
thread_title:  Reference 6 missing 

message: The article emphasizes at various spots that there are no control rods in this reactor design; however, later, it states:
"All the control rods were removed"
How does that fit together?
Intrr (talk) 19:14, 26 March 2011 (UTC)
thread_title:  Control rods: Article contradicts itself 

message: I would have to say that the statements about graphite burning are the results of original research.  There are no citations regarding this. It was just presumed that because it was a form of Carbon that it would readily burn.  
In fact, graphite is not combustible, or only slightly combustible at high temperatures.  There is also pyrolytic Carbon that is also used in making TRISO fuel elements that is only combustible at high temperatures.  Some actual research should be done on the subject regarding just how combustible graphite is under the temperature conditions in the reactor.
Tyrerj (talk) 06:00, 23 January 2015 (UTC)
replies: text: Chernobyl. That is all.178.15.151.163 (talk) 15:12, 9 August 2016 (UTC)
thread_title:  Combustible graphite 

message: The article says: "it is difficult to re-use pebble-bed reactor waste for nuclear weapons"
Since it is impossible to make nuclear weapons from reactor "waste", that really makes no difference.  Reactor waste contains Plutonium.  However, it is what is called reactor grade Plutonium.  If you read Wikipedia, you will find that there is more than one isotope of Plutonium and that only Plutonium-239 is desirable for making weapons.  Plutonium that contains over 10% of Plutonium-240 is simply not suitable for making weapons.  The Plutonium in reactor waste not only contains more than that much 240 but also contains 241 and 242.  I suggest that you do some research instead of repeating incorrect anti-nuclear propaganda.
Tyrerj (talk) 06:27, 23 January 2015 (UTC)
thread_title:  The myth of using spent reactor fuel for nuclear weapons 

message: "In spite of the limited amount of radioactivity released (0.1 GBq 60Co, 137Cs, 233Pa)a commission of inquiry was appointed. The radioactivity in the vicinity of the THTR-300 was finally found to result 25% from Chernobyl and 75% from THTR-300."
This is incorrect and probably a lie coming from an editor who should know the final report of that commission. It rejected all claims coming from anti-nuclear-power-activists regarding the 75 % as unfounded. It actually states that the activity in the vicinity coming from the plant was so small that it could not be measured and was not detected by the installed measuring stations and estimated it based on the measured emissions(!) of that week using a distribution model to be less than 1 Bq / m² of soil surface at maximum (while the immissions(!) coming from Chernobyl in that area at that time being around 10000 Bq / m²).
The final report of that commission:
https://www.landtag.nrw.de/portal/WWW/dokumentenarchiv/Dokument?Id=MMV10%2F561%7C1%7C0
Jwalter (talk) 08:24, 31 May 2016 (UTC)
thread_title:  THTR-300 - Commission and 75 % of activity 

message: Project Timberwind used particle-bed reactor designs - are they considered pebble-bed reactors ? - Rod57 (talk) 17:40, 15 April 2021 (UTC)
replies: text: I still don't know - but PB reactors seem to use 60mm diam 'pebble' elements, each containing many 1 mm diam coated fuel particles. - Rod57 (talk) 09:53, 9 October 2021 (UTC)
thread_title:  Does pebble-bed include particle-bed 

message: There seems to be a problem with the sketch of the reactor. Where does it come from? There's no source listed.
Here's what I found disturbing: the arrows that illustrate gas circulation and these arrows suggest that the cooling gas is forced down the pebble bed and then down through the heat exchanger which is the opposite of natural gas circulation due to temperature and density changes. Without pumping, the gas would heat and rise in the reactor and cool down and fall in the heat exchanger. This natural circulation seems like a fail-safe for the pumps. Also, forcing the flow down through the pebble bed could cause convection heat bubbles to form - the hotter the area, the more it would resist the forced downwards flow (the opposite would happen in the exchanger, though there the linear structure and coolant flow make it much less relevant). 
- not signed by User:78.11.145.7 06:18, 26 July 2021‎‎
: The sketch may be based on similar in  which has comments that also question the direction of gas flow. - Rod57 (talk) 09:00, 9 October 2021 (UTC)
replies: text: has a more detailed diagram that also shows gas flow down in the chinese HTR-10, so I guess down is correct. That blog refs China 210 MWe pebble bed reactor starts construction April, 2011 which has more refs. - Rod57 (talk) 09:48, 9 October 2021 (UTC)

text: AVR reactor says its helium coolant flows UP through the core. - Rod57 (talk) 18:08, 9 October 2021 (UTC)
thread_title:  Reactor sketch - gas circulation direction?