|
So did Legasov's knowledge of the unearthed report mean that when people were dunking on him in episode 1 for his inability to explain how the explosion was possible he knew how but didn't say because he knew it was embarrassing for the state?
|
#
?
May 28, 2019 16:07
|
|
|
|
| # ? Jun 9, 2024 07:04 |
|
|
Chef Boyardeez Nuts posted:So did Legasov's knowledge of the unearthed report mean that when people were dunking on him in episode 1 for his inability to explain how the explosion was possible he knew how but didn't say because he knew it was embarrassing for the state? I think in real-life and the show, at that point Legasov hadn't connected the reactivity rise with a SCRAM to the event yet.
|
|
#
?
May 28, 2019 16:16
|
|
|
Chef Boyardeez Nuts posted:So did Legasov's knowledge of the unearthed report mean that when people were dunking on him in episode 1 for his inability to explain how the explosion was possible he knew how but didn't say because he knew it was embarrassing for the state? He wasn't fessing up to his knowledge of the issues of that type of the reactor, because those issues were a state secret. And he also didn't know that those issues were what caused this specific explosion until the other scientist connected the dots for him with her research.
|
|
#
?
May 28, 2019 16:18
|
|
|
Two technical questions and I apologize if they've been covered already. I've done some reading about "reactor poisoning" but don't really understand it. I understand that it means that there are too much of the wrong sort of isotopes in the core? What are the consequences of that? Does the reaction stop, become uncontrollable, something else? Why were the control rods tipped with graphite? I get that the control rod displaced water, so the portion of graphite slowed neutrons and made more fission occur. But, why do you want your control rod to do that if all the rest of it is boron to reduce the amount of fission?
|
|
#
?
May 28, 2019 16:48
|
|
|
Now I want to go back and rewatch that scene because I recall a reasonably pregnant pause. It would be neat if they built in him rationalizing if whether earning bullet for telling them that a foundational portion of Soviet nuclear was flawed would actually make a difference.
|
|
#
?
May 28, 2019 16:51
|
|
|
Chef Boyardeez Nuts posted:Now I want to go back and rewatch that scene because I recall a reasonably pregnant pause. It would be neat if they built in him rationalizing if whether earning bullet for telling them that a foundational portion of Soviet nuclear was flawed would actually make a difference.
|
|
#
?
May 28, 2019 17:02
|
|
|
ZorajitZorajit posted:Two technical questions and I apologize if they've been covered already. Pretty much. Neutron poisons such as xenon-135 (which is a product of uranium fission via iodine-135) are very good at absorbing neutrons, so they end up interfering with the chain reactivity that makes a nuclear reactor work and reduce the power output. ZorajitZorajit posted:Why were the control rods tipped with graphite? I get that the control rod displaced water, so the portion of graphite slowed neutrons and made more fission occur. But, why do you want your control rod to do that if all the rest of it is boron to reduce the amount of fission? Your guess is as good as mine, but officially it was to stop the water from filling the void left by a control rod's withdrawal. Graphite's also a lubricant, so it might've helped insertion and withdrawal somewhat.
|
|
#
?
May 28, 2019 17:16
|
|
|
ZorajitZorajit posted:I've done some reading about "reactor poisoning" but don't really understand it. I understand that it means that there are too much of the wrong sort of isotopes in the core? What are the consequences of that? Does the reaction stop, become uncontrollable, something else? it means there is too much of some neutron absorbing substance in the reactor, which slows down the reaction. think of it like not enough oxygen being supplied to a combustion engine. the presence of a reactor poison "chokes" the fission reaction. isotope byproducts from the fission reaction can build up in the reactor and have to be managed ZorajitZorajit posted:
from a reddit thread: quote:The control rods and the safety rods of an RBMK reactor are inserted into the reactor core from above, except for 24 shortened rods which are inserted upwards and which are used for flattening the power distribution. A graphite rod termed a 'displacer' is attached to each end of the length of absorber of each rod, except for twelve rods that are used in automatic control. The lower displacer prevents coolant water from entering the space vacated as the rod is withdrawn, thus augmenting the reactivity worth of the rod. The graphite displacer of each rod of all RBMK reactors was, at the time of the accident, connected to its rod via a 'telescope', with a water filled space of 1.25 m separating the displacer and the absorbing rod (see Fig. 1). The dimensions of rod and displacer were such that when the rod was fully extracted the displacer sat centrally within the fuelled region of the core with 1.25 m of water at either end. On receipt of a scram signal causing a fully withdrawn rod to fall, the displacement of water from the lower part of the channel as the rod moved down- wards from its upper limit stop position caused a local insertion of positive reactivity in the lower part of the core. The magnitude of this 'positive scram' effect depended on the spatial distribution of the power density and the operating regime of the reactor.
|
|
#
?
May 28, 2019 17:20
|
|
|
Chef Boyardeez Nuts posted:So did Legasov's knowledge of the unearthed report mean that when people were dunking on him in episode 1 for his inability to explain how the explosion was possible he knew how but didn't say because he knew it was embarrassing for the state? Pretty sure he didn't know. He even says "Even when I saw the reactor was exposed I still didn't put them together" It was only after the painstaking recreation that it appears he realizes what happened.
|
|
#
?
May 28, 2019 17:22
|
|
|
ZorajitZorajit posted:Two technical questions and I apologize if they've been covered already. "Reactor poisoning" is referring to buildup of Xenon-135 in the core. Xe-135 is a fission product, meaning it's one of the elements the Uranium splits into. It is also a strong neutron absorber, which means it reduces the reaction rate in the same way the control rods do. But when it absorbs a neutron, it becomes Xe-136 and is no longer an absorber. When a reactor has been running at a steady power level for a long time, Xe-135 is being created at the same rate its being converted to Xe-136. But when a reactor was running at high power and is reduced to low power as the one at Chernobyl was before the explosion, there's too much Xe-135 in the core making it difficult to sustain a reaction. At that point the reactor is "poisoned" and should be shut down for several hours to allow the Xe-135 to decay naturally before restarting it. At Chernobyl they kept trying to increase the power by removing control rods and disabling safety systems. Once the reaction rate spiked, the Xe-135 converted to Xe-136 increasing the reactivity further. So it's another factor besides the positive void coefficient causing the reactor power to increase uncontrollably. I don't understand the control rod tips as well, but my understanding is that the graphite tips are already in the middle of reactor when the rods are fully retracted, and the purpose is to increase the effectiveness of the control rods by having the retracted ones increase reactivity. But the reactor is very large and the rods move slowly. The graphite tips moving into the bottom of the reactor caused the power in that part to spike, and then the rods jammed at the beginning of the accident. The changes made to the other RBMK reactors after the accident were not to replace the graphite tips, just to upgrade the motors and make the rods move faster during a SCRAM.
|
|
#
?
May 28, 2019 17:36
|
|
|
Arrion posted:I don't understand the control rod tips as well, but my understanding is that the graphite tips are already in the middle of reactor when the rods are fully retracted, and the purpose is to increase the effectiveness of the control rods by having the retracted ones increase reactivity. But the reactor is very large and the rods move slowly. The graphite tips moving into the bottom of the reactor caused the power in that part to spike, and then the rods jammed at the beginning of the accident. The changes made to the other RBMK reactors after the accident were not to replace the graphite tips, just to upgrade the motors and make the rods move faster during a SCRAM.  (from here https://engineering.stackexchange.com/questions/25006/how-did-the-rbmk-control-rod-design-cause-an-increase-in-reactivity-when-moved-d) Here's a handy graphic explaining it. The normal position is position II on that graphic. You can see how when it goes from position II to III the graphite tip passes through the fuel element layer, which would increase power as more neutrons are moderated. So then you get the steam flash boiling which jams the rod in the position where it's actually increasing the speed of the reaction instead of reducing it. Edit: Fixed graphic. CainFortea fucked around with this message at 18:42 on May 28, 2019 |
|
#
?
May 28, 2019 17:53
|
|
|
Okay. I think I get it. Reactor poisoning happens when too much by-product isotope slows down the reaction by absorbing neutrons. The by-product will decay on its own if the reactor is shut down. But when the reactor is pushed to produce more power, that also gets rid of the poison, and without the poison now even more power is being produced. The control rods had carbon because the difference in moderation between carbon and boron is greater than that between water and boron. I'm still not sure when you would ever want to retract the carbon (position II in the diagram in the link), but I'm also not a Soviet nuclear plant worker who doesn't see graphite on the ground. VVVVVV: Okay, that makes sense. Instead of the control being between position IV and position III, the reaction is controlled by moving between II and III. ZorajitZorajit fucked around with this message at 18:57 on May 28, 2019 |
|
#
?
May 28, 2019 18:37
|
|
|
ZorajitZorajit posted:The control rods had carbon because the difference in moderation between carbon and boron is greater than that between water and boron. I'm still not sure when you would ever want to retract the carbon (position II in the diagram in the link), but I'm also not a Soviet nuclear plant worker who doesn't see graphite on the ground. The positions aren't really a linear thing. The idea is that at III the control rod is actually increasing the reaction rate so it's like an accelerator. By transitioning between III and II you're in control of how fast the reaction is going. Since the water in the RBMK reactors is used to absorb neutrons it doesn't moderate the reaction so much as slow it down. So it's almost like driving heel/toe, with II as the brakes and III as the accelerator. Position IV is full shutdown. One of the flaws here is that it has to get from brakes to full acceleration before it can get into shutdown mode. Which combined with other stuff they were doing for the test and just standard soviet safety culture turns it from a problem to be concerned about to explosion. Also IIRC neutron absorption and neutron moderation are different. With absorption the neutron just stops. Moderation causes the neutron to lose some energy by bouncing off, which allows it to interact fully with other fuel atoms, which is what causes the reaction to speed up.
|
|
#
?
May 28, 2019 18:49
|
|
|
The RBMK also had the unique void coefficient characteristic in which at certain control rod depth you would see a increase in power output instead of a decrease. This caused a near miss incident in a Leningrad power plant but due to the compartmentalized nature of the Soviet energy industry this design flaw was not communicated to other plants. Given the economic conditions of the Soviet Union and also the inability to make high tolerance components it's not surprising that the USSR went this route in the design of the nuclear plants.
|
|
#
?
May 28, 2019 19:12
|
|
|
Okay, so, Chernobyl happens in the states today and venture capital funds roof cleanup "biorobots." What do you name your app and how do you gamify it?
|
|
#
?
May 28, 2019 19:29
|
|
|
very carefully
|
|
#
?
May 28, 2019 19:33
|
|
|
So the graphite is radioactive because it's got lots of particles of radioactive uranium (or whatever) isotopes in pores inside it, right? The graphite itself is not an unstable isotope of carbon?
El Jeffe fucked around with this message at 19:38 on May 28, 2019 |
|
#
?
May 28, 2019 19:34
|
|
|
ZorajitZorajit posted:Okay, so, Chernobyl happens in the states today and venture capital funds roof cleanup "biorobots." What do you name your app and how do you gamify it? TaskRoentgen
|
|
#
?
May 28, 2019 19:36
|
|
|
El Jeffe posted:So the graphite is radioactive because it's got lots of particles of radioactive uranium (or whatever) isotopes in pores inside it, right? The graphite itself is not an unstable isotope of carbon? Neutron bombardment of graphite (Carbon) turns into a radioactive material. When the Chernobyl reactor containment shield buckled it flung burning radioactive chunks of graphite all over creation. https://www.sciencedirect.com/science/article/pii/S0022311518302538
|
|
#
?
May 28, 2019 19:40
|
|
|
ZorajitZorajit posted:Okay, so, Chernobyl happens in the states today and venture capital funds roof cleanup "biorobots." What do you name your app and how do you gamify it? Literally just toreba crane game but with chunks of graphite instead of Naruto headbands
|
|
#
?
May 28, 2019 19:45
|
|
|
etalian posted:Neutron bombardment of graphite (Carbon) turns into a radioactive material. Oh neat. What carbon isotope is it then? I'm only seeing C-14 mentioned in that paper at first glance. Or is it not even carbon anymore?
|
|
#
?
May 28, 2019 19:48
|
|
|
El Jeffe posted:Oh neat. What carbon isotope is it then? I'm only seeing C-14 mentioned in that paper at first glance. Or is it not even carbon anymore? graphite, which during operation, becomes radioactive due to the neutron activation of carbon and the various other impurities inherent within the material
|
|
#
?
May 28, 2019 19:51
|
|
|
El Jeffe posted:Oh neat. What carbon isotope is it then? I'm only seeing C-14 mentioned in that paper at first glance. Or is it not even carbon anymore? Yes basically the neutron absorption over time as well as the inate processed graphite chemistry means the moderator material will become highly radioactive over the life of the plant.
|
|
#
?
May 28, 2019 19:53
|
|
|
etalian posted:When the Chernobyl reactor containment shield buckled it flung burning radioactive chunks of graphite all over creation. Speaking of burning things, the latest episode had those soldiers burning the crates. I was just sitting there all  at it. Why in the gently caress would you burn ANYTHING that close to the fallout exclusion zone? Just add more loving particulates you're breathing in which may be carrying alpha emitters.
|
|
#
?
May 28, 2019 19:56
|
|
|
CainFortea posted:Speaking of burning things, the latest episode had those soldiers burning the crates. I was just sitting there all vodka ration provides protection
|
|
#
?
May 28, 2019 20:01
|
|
|
CainFortea posted:Speaking of burning things, the latest episode had those soldiers burning the crates. I was just sitting there all making soldiers burn toxic bullshit is a pretty common hazard of being a soldier the crates are presumably not that bad since they're being shipped in from outside, not manufactured on site, and they're probably burning everything to dispose of it rather than ship anything away from the site
|
|
#
?
May 28, 2019 20:11
|
|
|
etalian posted:vodka ration provides protection Not even a joke, according to the showrunners' research. So little was commonly known about radiation back then in the USSR, it was honestly believed among commoners that this helps. It helped with so many other things, right? 
|
|
#
?
May 28, 2019 20:16
|
|
|
CrazyLoon posted:Not even a joke, according to the showrunners' research. So little was commonly known about radiation back then in the USSR, it was honestly believed among commoners that this helps. It helped with so many other things, right?   
etalian fucked around with this message at 20:26 on May 28, 2019 |
|
#
?
May 28, 2019 20:23
|
|
|
|
|
#
?
May 28, 2019 20:25
|
|
|
luxury handset posted:making soldiers burn toxic bullshit is a pretty common hazard of being a soldier Well, sure. I just would be walking around with my breath mask all the time and not burning things.
|
|
#
?
May 28, 2019 20:39
|
|
|
CainFortea posted:Pretty sure he didn't know. He even says "Even when I saw the reactor was exposed I still didn't put them together" Remember there were hundreds of people collaborating in the background to figure this out. Legasov's reaction I think is meant to represent the scientists who knew about the flaw coming the conclusion that this might be the cause over time. Even though the report was suppressed, there were still a fair number of scientists who were working on this that knew about it from the investigation work on past incidents. As for the problem itself, no one had ever contemplated that it would result in a Chernobyl-like event. It took some time before enough information was put together about happened in the lead up (most notably, the control rods being almost entirely retracted) that scientists who had known about the flaw started connecting the dots and thinking about what would happen if you combined the positive void coefficient with the reactor in the state it was when they hit the shutdown. nessin fucked around with this message at 21:56 on May 28, 2019 |
|
#
?
May 28, 2019 21:43
|
|
|
Russians are actually full of Proverbs. Moreso than you'd expect. A People's Tragedy is a great comprehensive history of modern Russian events from ~1860 to the late USSR.
|
|
#
?
May 28, 2019 22:45
|
|
|
The poor guy who had to stand inside the roof hole to instruct the biorobots must have been getting some serious roets-to-the-face. Weren't the biorobots used on all 3 of the rooftops? I thought I remember reading that the other robots eventually failed as well.
|
|
#
?
May 28, 2019 22:52
|
|
|
Sometimes you eat bear, sometimes bear eat you.
|
|
#
?
May 28, 2019 22:54
|
|
|
Gorson posted:The poor guy who had to stand inside the roof hole to instruct the biorobots must have been getting some serious roets-to-the-face. Weren't the biorobots used on all 3 of the rooftops? I thought I remember reading that the other robots eventually failed as well. Yeah the russians brought some lunar rover prototypes which had rad hardened electronics but they got entangled in the debris. So eventually they went the bio-robot solution.
|
|
#
?
May 28, 2019 22:55
|
|
|
Learn how to pronounce: "ничего не поделаешь" Congrats on your Russian fluency.
|
|
#
?
May 28, 2019 23:27
|
|
|
So now that we're almost done with the cleanup part and politics seems to be the main focus of the last episode, there's something I don't understand. Is Legasov just frequently wrong? Every time he's talking about the damage done by Chernobyl it doesn't seem to coincide with what we know actually happened. He's giving that presentation to the Central Committee and he's talking about needing almost a million men to assist with the cleanup and that either thousands or tens of thousands will die. But that poo poo didn't happen right? I know the number isn't exactly clear, but it's generally accepted that less than 100 people died in the immediate aftermath, and while there were certainly hundreds more than died later or were severely hosed up, why is he talking about tens of thousands?
|
|
#
?
May 29, 2019 00:04
|
|
|
counterfeitsaint posted:So now that we're almost done with the cleanup part and politics seems to be the main focus of the last episode, there's something I don't understand. The mortality rate for liquidators was more than double, iirc. Legasov is referring to the fact that most of those involved in the operation will die of cancer in their 30s and 40s as opposed to living into their 70s or 80s. In addition, a few hundred to a few thousand people died just from the evacuation of Fukushima: God only knows how many died in the Soviet evacuation...
|
|
#
?
May 29, 2019 00:14
|
|
|
counterfeitsaint posted:So now that we're almost done with the cleanup part and politics seems to be the main focus of the last episode, there's something I don't understand. He was the man responsible for figuring out how to make those bad outcomes not happen, and he did. He did do some things that later turned out to be unnecessary. For example, those miners dug under the reactor building in order to install a liquid cooling system. The fear was that the reactor core could eventually melt all the way through the concrete sub-basement and leech into the groundwater. It turned out that the nuclear slag wasn't hot enough for long enough to get through; they eventually just poured more concrete underneath instead of installing the coolant. But it was a possibility (in the show, he says he thinks there's a 40% chance) so he had to come up with a fix and put a lot of men at risk to get it done.
|
|
#
?
May 29, 2019 00:16
|
|
|
|
| # ? Jun 9, 2024 07:04 |
|
|
So is there nowhere to just buy access to this series? This is the only HBO series I want access to.
|
|
#
?
May 29, 2019 00:27
|
|