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Diagram of the reactor vessel. Gray represents the debris/silica/boron mixture thrown by military helicopters. The green circle is the inverted 1000 ton vessel lid, at approx 15 degrees from vertical.
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From: anonymous (Mon Apr 25 18:54:24 2005) i had to get my russian friend to translate this for me |
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From: lkarlov (Sat Apr 30 09:32:18 2005) I have question about preassurized water reactors. Why do western PWR's have only 2 primary loops? Isn't that dangerous? What if both loops fail? Are there backup? Russian VVER's have up to 6 loops, isn't that better? |
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From: person (Mon May 2 19:29:34 2005) 2 primary loops? i am not too sure if you know what a primary loop is. a primary loop is the loop of water that actually cools the core. the secondary loop gets the heat from the primary loop and turns to steam and then is run through the turbine (the primary loop is pressurized, so it doesn't boil, hence a presurized water reactor) in in thermal reactors the water actally has to go all through the core and between the fule rods to work, so having a backup primary loop doesn't make sence. western reactors have an array of backup pumps for the cooling loops to make sure that in the event of an emergancy they still have coolent. another problem with having alot of loops is that you waste alot of energy that could go through the turbines. although i dont know too much about VVER's i sereously doubt they have six coolent loops. taht would meant that they exchange the heat six times! the most i know of is the CANDU (canadian) reactors that have three cooling loops. |
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From: lkarlov (Tue May 3 03:58:47 2005) I know what a primary loop is. Sorry, my mistake. VVER-1000 doesn't have 6 loops but it does have 4 loops. I don't get something about backup pumps. Are backup pumps connected to primary loop pipes (so main pumps are simply bypassed) or are there other pipes other than primary loop pipes that lead to the core to provide backup cooling? And isn't it safer to have 4 loops, so you have 2 loops online, and in case of emergency you start other loops? |
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From: person (Wed May 4 21:49:25 2005) backup pumps are connected to the primary loop pipes, but there is somthing called high pressure coolent injection, which puts a bounch of coolent from a different line. i think you are asking about how the water in the rbmk reactor goes into 2 seperate turbines, right? i can see how someone would see that as safer... seeing as i am more knowlageable about the reactor itself and not the cooling systems, i dont know, it seems like your right, but i know a guy who runs reactors and is getting a phd in nuclear phisics, im sure he woudl know! ill ask him. i kept thinking you were saying 4 loops in parralel, which wouldn't make more sence because your heat transfer wouldn't be as efficient and it wouldn't be any safer (probly less safe, because there is more to go wrong) |
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From: lkarlov (Thu May 5 12:11:31 2005) Ok, I get it. There are backup pumps installed on primary loops, but there is also additional emergency coolant injection system. no, I wasn't taking about RBMK, I was talking about PWR reactor. Why wouldn't be safer to have more primary loops in PWR reactor? Why the heat transfer wouldn't be efficient then? I get the part where you said that more loops means more equipment meaning that more could go wrong. But this also means that you have more redundant systems, wouldn't you say? |
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From: lkarlov (Thu May 5 12:14:49 2005) Did you mean that if you had more loops, the steam generators wouldn't be getting enough heat to generate enough preassure for the turbines? |
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From: person (Thu May 5 22:31:30 2005) aaa! i think we both dont know what the other is talking about! :D haha, okay... i talked to taht guy who runs the reactors, he said that on the pressurized water reactor he works on, there are two loops that can both cool the nuclear portion of the reactor. they are conected during normal use, but if one of the loops bursts, they can block water to that loop. (in the event of an emergency, one of those pipes bursts, ect, they can block water to those pipes, and the other pipes and pumps are enough to cool the reactor) so this is kind of like having two primary cooling loops. when you said 4 cooling loops, i took that to mean that there were 4 loops that transfer heat to the next one on the list. 1 transfers to 2, 2 to 3, 3 to 4, and 4 to the turbine. if it was that way it could work, but you would be wasting alot of heat energy during the transfers. i think what you mean is that 1 and 2 are used to cool the core. 1 transfers to 3 which runs the turbine. 2 transfers to 4 which runs another turbine. yes i can see how that would be safer, adn as i said abouve, it is used. each of these loops has backup pumps and shutoff valves as well. |
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From: lkarlov (Fri May 6 01:56:05 2005) Yes, now I know what were you talking about. The way you described wouldn't be efficient (1 to 2, 2 to 3, 3 to 4....) |
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From: person (Fri May 6 19:55:00 2005) thats why i wanted to draw a picture, but it is kind of hard to do that over the interne! |
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From: sen (Sun May 7 19:09:50 2006) The idea behind the two primary loops and two SECONDary loops is to contain contamination and radiation within the sheilded vessel... you have two primary loops which contain the moderator or coolant, which transfers its heat through a sort of "boiler," furthermore that steam is then transferred outside the shielded vessel to the turbines. If you were to have JUST the primary loops the steam from those loops would be very highly contaminated, and as such contaminate your entire engineroom, including the turbines... not a very good idea. Although, I know of at least one boiling water reactor that exists, and yes, the entire turbine area is contaminated, making for some very tricky maintenance... I believe that it is a U.S. reactor also, where though I am unsure. |
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From: Matt (Mon May 8 00:12:22 2006) Fascinating. Thank you for a REAL discussion. It's nice to get actual information without all the filler-babble. |
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From: random person (Fri Dec 8 20:54:46 2006) I wish that you could translate the words. |
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From: TRANSLATOR!!!! (Wed Mar 28 18:53:00 2007) I'm russian and I can translate that!!! You're in luck!!!! Below the green circle it says (in red) place where was active zone, I'm not that good but I know what that means!!!!, I swear to God, no fingers crossed promise! |
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From: npj.ru/arioch (Fri Apr 27 07:20:53 2007) RBMK scheme in much detail - but in russian http://reactors.ru/rbmk/03_rbmk.htm "Enhanced RBMK" scheme - http://www.iae.lt/inpp_en.asp?lang=1&subsub=29 To add to this picture. "Cx" stands for "scheme" - the internal codename for part of the constrauction. Say, "Sceme E" was a lid with its steam tubes and control rods. At the top there are Nothern and Southern Barrel-Separators Gray is just "Debris" Numbers are numbers of technical rooms - compare to Fig.5 at http://www.kiae.ru/rus/inf/chnpp/pr_fcm.htm "ÏÐÊ" maybe sttabds for "under-reactor rooms" "HBK" - dunno |
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From: Scott (Fri May 11 12:12:57 2007) Why didn't they draw the lava/fuel? |
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From: dtebar@mad.scientist.com (Tue Aug 28 23:45:56 2007) I saw a Nova documentary where Gorbachev says that the engineers were worried that the melted fuel may get to a level below where there was a pool of water because this could have ignited it in a worse explosive way! Is this true? --DTebar |
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From: wildespace (Sun Sep 16 11:03:09 2007) Yes, it's true. They drained that water away, so the threat passed away. |
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From: sebastian (Fri Jan 4 15:05:48 2008) how did they drain the water away? are there detailed reports on the things that happened under the reactor? |
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From: Scott (Fri Oct 2 12:00:31 2009) If I recall correctly one or more Soviet firefighters (perhaps military) had to volunteer to dive into the radioactive pool under the reactor and manually open a valve to drain away the water--resulting in the death (and it was always certain that they would die) of the volunteers. I could be wrong though, it has been quite awhile since I read an actual account of the accident and clean-up. |
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From: gracejames7@aol.com (Mon Jan 4 09:04:25 2010) For the discussion going on about Cooling loops-the design of Pressurized Water Reactors is infinitely less dangerous than Graphite Core Reactors like the ones at Chernobyl. Usually they are refered to as having 3 loops because they count the loop from the cooling lake or towers through the main condensor. If plant design at Three Mile Island was similar to Chernobyl the spread of contamination would have been as bad or worse. There are currently 69 PWRs and 35 BWRs operating in the US for power generation,also 30 or so research and test reactors. I work in BWRs and PWRs frequently during re-fuleing |
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