Talk:Radioisotope thermoelectric generator

message: Hi All:
Nice article, but there's a minor bug in it --
the Soviet US-A RORSATs didn't use RTGs, they
actually used full-blown fission reactors, 
which are a somewhat different breed of animal.
See:
   http://www.vectorsite.net/tarokt3.html#m5
-- for details.  I have made the appropriate 
changes.  Suprised nobody caught that one.
(Also added a bit about use of "plutonium
cells" -- micro-RTGs -- in heart pacemakers.)
gvgoebel
:Thanks for fixing up the RORSAT part of the article. I think I wrote that so its my fault that it wasn't completely truthful. I made some small changes to what you had written to make it sound more 'encylopediac' - like the idiom 'push comes to shove'.--enceladus 22:15, 12 Aug 2004 (UTC)
replies: text: I have moved the RORSAT section to the RORSAT article. It didn't really have any relevance here. Bobbis 00:38, 27 Oct 2004 (UTC)
thread_title:  RORSAT Reactors 

message: The life span section needs to be recalculated using the correct 1/2 life vale of 87.7 y. I'm horrible at math ......--Deglr6328 05:13, 19 Mar 2005 (UTC)
thread_title:  Maths 

message: It's important to distinguish which external links were actually used as sources and which are simply provided for the reader's edification.  I haven't attempted to classify which of the currently listed links were actually used as references, so I just created a new section for external links only.  Somebody should go through and sort the links.  (This is important both for reliability and for potential Featured Article status). --Andrew 17:09, Mar 22, 2005 (UTC)
:All but one link provided information (or a image) that is used in the article, the outlier I moved. I would not like this to become a feature article because of the controversy (scaremongers) that would come to this article. Perhaps we would have to place more information about the safety, concerns and myths-debunks of the 238Pu fuel used first. --BerserkerBen 19:51, 23 Mar 2005 (UTC)
thread_title:  References vs. External links 

message: Is there a good reason why a scientific article in an international forum is still using imperial units?
:Probably because it will have been written using American sources which won't be using metric. Be bold and fix it. Evil Monkey∴Hello 22:48, 24 August 2005 (UTC)
thread_title:  Units? 

message: Suggest adding data about physical and electrical characteristics of certain well-known RTGs. E.g, Pioneer 10/11, Voyager 1/2, Galileo and Cassini probes: mass, size, initial and later electrical output.
Suggest also contrasting RTG output/weight/complexity characteristics with competing space power sources such as batteries, solar cells, fuel cells and nuclear reactors. Joema 06:29, 9 December 2005 (UTC)
thread_title:  Need Info on Specific RTGs, Contrast with other Power Sources 

message: It is known that plutonium 238 degrades by alpha emission. Then, the alpha particles slow down, gain electrons, and form helium gas. Do the pressures created by the helium gas in the small internal space of an RTG ever create problems in the RTG? Polonium 00:50, 18 January 2006 (UTC)
replies: text: Most RTG design diagrams seem to show a gas relief valve, I guess that is where the helium escapes… hum I wonder if that could have been a contributor to that anomaly on how  Pioneer 10 was going off course?  --BerserkerBen 02:10, 18 January 2006 (UTC)

text: I'm no expert, but the article says the contrary: RTGs produce energy mostly by alpha or beta decay. And obviously they do not use use U-238, which is too slow to disintegrate, but rather Pu-238, which has a half-life of 87.74 yr. —Edgar.bonet (talk) 19:46, 11 March 2014 (UTC)
replies: text: Plutonium-238 and Uranium-238 are different things. And Pu-238 RTGs indeed produce their power by decay only. A teeny tiny fraction of those decays are spontaneous fission and that does sometimes release neutrons, but the value is almost certainly below natural background (yes, there is background neutron radiation) and I'd assume especially so in outer space, where all sorts of weird cosmic ray spallation goes on all the time without an atmosphere or a magnetic field to shield it... Hobbitschuster (talk) 14:50, 22 February 2022 (UTC)
thread_title:  Helium Accumulation 

message: A lighthouse needs more that 10 watts of electricity. How can a lighthose RTG wave an electrical power output of 10 watts (they do not use hundreds of RTGs)? 72.139.119.165 19:28, 25 February 2006 (UTC)
thread_title:  Disputed 

message: The safety section of the article seems somewhat POV.  For example I have just replaced the paragraph that reads Several tons of plutonium-239 have been released into the atmosphere by over 2,000 nuclear weapon tests. The plutonium-238 used by RTGs is designed to prevent release under the worst possible scenario. It seems to be full of platitudes like this - comparing Pu-238 with Pu-239 is not really reasonable since Pu-238 is radiologically a more dangerous material–ingesting a quantity of Pu-238 would give you nearly 300 times the alpha radiation dose of ingesting the same amount of Pu-239.  And the main reason that atmospheric testing was stopped was because of the amount of radioactive material released into the atmosphere. And what is the "worst possible scenario", how about an RTG falling into the hands of terrorists, the fuel removed, ground into dust and used in a radiological weapon.  Unlikely, but possible.  I suspect that this doesn't happen because of the efforts of security and law enforcement people rather than anything to do with the design of the device.
The section also only addresses spacecraft RTGs, which must be the safest type, since there aren't many of them, no expense is spared in designing, building and looking after them, and unless something goes very badly wrong indeed spend their working life in space.  But not a word about those rotting ex-Soviet RTGs shown in the picture.  Surely that type of RTG must represent a far bigger danger. Jll 10:29, 22 June 2006 (UTC)
thread_title: POV?

message: "They pose a hazard if the wearer is shot in the chest with a gun."-
Just thought i'd point this out... I think getting shot in the chest with a gun has many disadvantages even to those of us without radioactive pacemakers.
I think it meant to other people. like paramedics who'd be unaware of the hazard.--Deglr6328 03:46, 9 October 2006 (UTC)
replies: text: No, I think someone is having fun "They pose a hazard if the wearer is shot in the chest with a gun. The wearer could suffer injury and even death in the case of a gunshot wound to the chest. Multiple stab wounds in the chest may also shorten the life expectency of 238Pu-powered RTG users."  I laughed until I cried a little - fun!  Non-encyclopedic (or unencyclopedic but hilarious nontheless.  —Preceding unsigned comment added by Jonathan888 (talk • contribs) 23:12, 2 October 2007 (UTC)
thread_title: Shot in the Chest?

message: Why doesn't the article mention normal radiation output let's say at 1 meter from the RTG surface when in normal operation? At least for a few RTG types. I haven't found any references for that information, but presumably someone has them. I bet that's far more a concern for those involved in spacecraft assembly than any remotly possible catastrophic launch accident.  —Preceding unsigned comment added by Rnbc (talk • contribs) 15:24, 3 September 2007 (UTC)
replies: text: I don't have a numeric answer for you.  But RTGs are typically fuelled by Pu-238, whose primary radiation output is alpha rays.  They will totally dissipate after passing through a few centimetres of air (alpha decay), and apparently cannot penetrate human skin; elsewhere in this page it's written that Pu-238 would be safe to hold in your bare hands, except that in large quantities its high temperature might burn you.  The story changes dramatically if you inhale or ingest Pu-238 particles, at which point the alpha rays would be in a position to do much more harm.24.222.2.222 12:48, 20 September 2007 (UTC)
replies: text: The decay chain produces gamma emmiters, and since Pu238 decays rather quickly than becomes a problem even after a few months. I've seen values as high as 100rad/year quoted for Pu238-powered pacemakers (ok, at 2cm from the shell, mind you, but then they also don't contain many kilograms of Pu238). Rnbc 11:43, 18 October 2007 (UTC)

text: U-238 and Pu-238 are not the same thing. And Pu-238 decays to U-234, which while yes, in the Uranium-238 decay series is not the same thing as U-238. U-234 while longer lived than Pu-238 is still orders of magnitude shorter lived than U-238 and so you get to its daughters much faster than if you'd started with U-28... Hobbitschuster (talk) 14:47, 22 February 2022 (UTC)
thread_title: Radiation Output

message: *
--Stone 10:15, 30 April 2007 (UTC)
thread_title: New Ref

message: This is from the fuels section:
*For spaceflight use, the fuel must produce a large amount of energy per mass and volume (density).  Density and weight are not as important for terrestrial use, unless there are size restrictions.
This is badly written. It first states that mass and volume are important then in the next sentatnce it says that density (mass and volume) and wieght (basically mass) are not important unless there are size restrictions (volume and/or mass). 
Now mass is probably very important, what's stopping me from editing this is because I'm not familar with the typical cargo hold size for most rockets or space shuttles. Could be most of the time they have some space to spare since they try to slim back so much on the mass.70.132.15.229 (talk) 12:30, 31 December 2007 (UTC)
thread_title:  Baldly writen section, and unsure of correct information. 

message: Are non-stop voyages real? I just read about Voyager 1 launched in 1977, still alive and kicking now some 10 billion miles away from earth, without power replacement. So, who needs oil? Anwar (talk) 18:42, 3 May 2008 (UTC)
replies: text: "Most RTGs use 238Pu which decays with a half-life of 87.7 years. RTGs using this material will therefore lose 0.51 / 87.7 or 0.787% of their capacity per year. 23 years after production, such an RTG would produce at 0.523 / 87.7 or 83.4% of its starting capacity. Thus, with a starting capacity of 470 W, after 23 years it would have a capacity of 0.834 * 470 W = 392 W. However, the bi-metallic thermocouples used to convert thermal energy into electrical energy degrade as well; at the beginning of 2001, the power generated by the Voyager RTGs had dropped to 315 W for Voyager 1 and to 319 W for Voyager 2. Therefore in early 2001, the thermocouples were working at about 80% of their original capacity." (from the article page). So, yes the Voyagers are on *real* non-stop voyages still being powered well and will continue to be so for a good while yet to come ;>)Pomona17 (talk) 11:34, 2 August 2008 (UTC)
thread_title: Non-stop voyage

message: I added two models manufactured by Teledyne Isotopes and used by USAF. I didn't have time to glean more info from the cited open-source document, but I bet someone could! I am surprised at the nearly complete lack of reference to US-built units. Please add more to this article if you can find the info! Highspeed (talk) 05:18, 19 January 2009 (UTC)
thread_title:  U.S. RTG's 

message: The article says: "this isotope [Sr-90] has [..] much lower energy density". In fact Sr-90 has twice the power of Pu-238, most of which is from Y-90 decay. If weight is meant to include shielding etc, the power density may actually be lower for strontium RTGs, but NOT for the isotope itself.  —Preceding unsigned comment added by 87.123.76.165 (talk) 11:16, 22 February 2010 (UTC)
replies: text: I think someone confused Sr-90 bare metal and strontium titanate. The difference is about a factor of two. Hobbitschuster (talk) 14:44, 22 February 2022 (UTC)
thread_title:  Sr-90 power density 

message: In 1964 the CIA wanted to evasdrop on the Chinese testsite at Lop Nor in central Asia. Together with the Indian Intelligence Bureau (IB) they intended to place a RTG powered radio relais station in fall 1965 at the top of Nanda Devi (25.5 kft) in the Himalayan mountains. Unable to do the mission before winter they decided to secure the refrigerator sized device to a rocky outcropping and return for it next year. In spring 1966 they discovered that it had been swept off the mountain by an avalanche.
Several expeditions were unable to locate the RTG again. Today the RTG is still believed several thousend feet below at the ground of an immense glacier the feeds the Ganges river. Another station placed on Nanda Kot (22.5 kft) operated several month until its antennas were covered in snow. This RTG, still at place, melted for itself under the snow a glistening cavern five feet across. This station was recovered. 
It is belived that the missing RTG melted itself to the ground of the glacier and keeps its own cave for some centuries. An Indian goverment report concluded that, once crushed, the 4 pound plutonium would be enough diluted to not pose a serious health risk for the many people who drink from the river Ganges. 
The story was first broken by Howard Kohn in an article entitled "The Nanda Devi Caper" in Outside magazine in 1978. Captain Manmohan Singh Kohli, the IB officer in charge of the project published his account in 2002: Spies in the Himalayas - secret missions and perilous climbs, University Press of Kansas. The latest book and first with extensive accounts from the American mountaineers is by Pete Takeda: An Eye on Top of the World, Thunder's Mouth Press, New York, 2006. 
With Takeda`s book and declassified documents from the Los Alamos National Laboratory a new fact about RTGs was discovered. The Pu 238 RTGs, partly by impurities, partly by alpha-neutron reaction, emitted considerable neutron radiation. Neither the American mountaineers nor the Indians were briefed on this danger for people close to the RTG. One of the Americans sees a link to his cancer.   
On the legendary CIA mission and the recently revealed neutron radiation of RTGs:
Peter Lee: Did A Plutonium Generator End Up in the Ganges?, CounterPunch, June 30, 2008 (On the Web).
-- Carel A. Kraft (talk) 17:12, 7 March 2010 (UTC)
thread_title:  CIA`s Lost Himalayan RTG 

message: The list is about accident involving RTG powered spacecraft, but are also listed RORSAT satellite that didn't used it (as stated in the period). Is there any reason to keep them in the list? 79.17.58.118 (talk) 10:07, 9 January 2012 (UTC)
replies: text: No. Removing it. Kolbasz (talk) 18:27, 2 April 2013 (UTC)
thread_title:  Safety record/edit 

message: I don't see any sources backing up the substantial claims made by the Stirling Radioisotope Generator. Where is this information come from? I've been following SRG development and I'm skeptical of "experimental results demonstrate that an SRG could continue running for decades without maintenance." As far as I know, current SRG development's primary issue right now, and why it hasn't replaced RTG's decades ago,is due to reliability and lack of positive experimental results.
Since I can't back up these claims with literature, than I can't add it. At the same time, the positive claims made (or even its existence) should not be added unless sources support it. In my humble opinion, the whole SRG reads like an advertisement written by people working on the project.  — Preceding unsigned comment added by T59Man (talk • contribs) 17:28, 7 November 2013 (UTC)
thread_title:  SRG issues 

message: http://spirit.as.utexas.edu/%7Efiso/telecon/McNutt_4-16-14/McNutt_4-16-14.ppt
--Craigboy (talk) 09:33, 25 April 2014 (UTC)
thread_title:  Great source on RTGs 

message: This article has a broken link to a PDF hosted on Dropbox and also improperly formatted references for 238Pu. Somerandomuser (talk) 02:19, 12 May 2017 (UTC)
thread_title:  This article requires maintenance 

message: The following passage seems to be duplicated from paragraph 4 in this section:
"The SNAP-27 heat source traveled to the moon in a graphite cask attached to the lander leg from which an astronaut removed it with a handling tool after a successful landing and placed it in the RTG."  SquashEngineer (talk) 15:47, 24 October 2017 (UTC)
thread_title:  Safety Section 

message: Has an RTG to operate on Venus (at 480 °C) been designed / studied ? - Rod57 (talk) 14:13, 29 September 2019 (UTC)
replies: text: You don't need one; solar and wind work. See Landis et al.'s Zephyr concept for a Venus rover. Double sharp (talk) 16:42, 27 December 2023 (UTC)
thread_title:  Has an RTG to operate on Venus (at 480 C) been designed / studied ? 

message: source: BBC. Onanoff (talk) 10:06, 11 January 2021 (UTC)
thread_title:  More on use in Soviet lighthouses 

message: I assume all RTGs using  that have ever been actually employed used some inert form of the stuff and not something utterly stupid like bare Strontium metal or Strontium Oxide or Strontium Carbonate (which significantly dissolves even in weak acids and is in a certain equilibrium with soluble versions even in a H2CO3 solution that forms when it comes into contact with water)... But of course I do not know it for a fact. Could this be spelled out clearer with sources? A lot of the danger from orphan sources with  depends on the chemical mobility of the Strontium. For Titanate or Zirconate or other forms it is relatively low. But for native metal it is basically through the roof. Yes, a malicious actor could through chemical processes extract Sr-90 in a more mobile form even from the chemically inert forms - but they'd have to a) know about it b) know where the Sr-90 is c) be able to get it and to it (remember: Those are by definition in remote places even if "lying openly on the ground" d) have the required shielding / remote handling / whatever capabilities or e) be desperate /stupid / suicidal enough not to care about radiation exposure during "manufacture". So yes, an "abandoned" Sr-90 RTG is not zero risk, but that is true for all of them. And unlike Actinides, Sr-90 does not have a critical mass, so the worst a malicious actor could do is a "dirty bomb" and not an actual nuclear explosive (yes, even Pu-238 has a critical mass. It may be impossible to actually build a "Pu-23 bomb", but what do I know?). Hobbitschuster (talk) 14:42, 22 February 2022 (UTC)
replies: text: Not a direct answer to your question, but may I suggest adding sources (https://www.url.com tags) to your recent additions? Between the lack of sourcing, and the tone of the additions (e.g. , , other phrasing that suggests that these are opinions and not facts), editors may be concerned about original research and may eventually remove the material unless it is cited and the tone reworked a bit. Hope this helps, thanks. –Novem Linguae (talk) 18:38, 22 February 2022 (UTC)
thread_title:  Sr-90 RTGs 

message: While there are pictures of glowing red pellets and spheres the temperatures are never mentioned other than the vague "A half-gram sample of 210Po reaches temperatures of over ." --Marc Kupper|talk 05:34, 25 June 2023 (UTC)
replies: text: What do published sources say?  Surely how hot the pellet gets depends on how fast you suck the heat away from it; if it's well-insulated, the temperature will climb beyond all practical limits - decay energies in the millions of electon-volt range would be equivalent to temperatures in the tens of millions of degrees. --Wtshymanski (talk) 02:45, 26 June 2023 (UTC)
thread_title:  What is the temperature of the radioactive sources? 

message: for rates of neutron generation by Pu238 vs. Pu238 dioxide. 
In subsection "Fuels/Pu248" it says:
"
However, plutonium(IV) oxide ...(with) natural ... oxygen emits neutrons ... ~2.3x103 n/sec/g of plutonium-238. This ... is relatively high compared to ... plutonium-238 metal. The metal containing no light element impurities emits ~2.8x103 n/sec/g of plutonium-238. These neutrons are produced by the spontaneous fission of plutonium-238.
"
The rate stated for PuO2 is _lower_ than the rate stated for pure Pu, despite the text being pointedly about the rate being higher, and a ratio of 5:1 is mentioned below this. So, one of the two numbers must be wrong.
jimswen (talk) 07:48, 4 March 2024 (UTC)
thread_title:  Self-contradictory numbers?