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Posted on 4/26/26 at 9:25 pm to rt3
I've often wondered if the test that night had never been done.
Would there have never been another accident so serious? Or by this accident occurring, did it by chance and the lessons learned, actually prevent another would be accident in another location at another time?
Would there have never been another accident so serious? Or by this accident occurring, did it by chance and the lessons learned, actually prevent another would be accident in another location at another time?
Posted on 4/26/26 at 9:36 pm to blueboy
quote:
I remember that the disaster response guys were all drunk as shite because they said it helped fight off radiation.
Hmm I’ll have to remember that one
Posted on 4/27/26 at 4:53 am to Bestbank Tiger
quote:
quote:
Positive void coefficient and graphite rod tips.
Why is that bad in layman's terms?
I was thinking about my reply last night as I drifted off to sleep and I realized that I don't think I explained it simply or maybe even explained the void coefficient at all. I woke up early this AM and thought I would take another shot.
First, when I talked about water it is important to distinguish water used in the core (where the nuclear reaction takes place) and the water in the steam generation side. They are not the same water they are in separate systems and on the power generation side you intentionally make steam. We are only talking about the core here.
Most western reactors use water as a moderator. The moderator slows down the neutrons. While counterintuative slowing down the neutrons actually speeds up the reaction because it increases the chance they will hit another neutron and continue the fission reaction. So when you remove water (create a void) either via leak or it boiling producing bubbles and voids in a western syle reactor the reaction slows down or stops. This is a negative void coeeficient. This is a built in automatic safety "valve" for when shite hits the fan.
The Russian RBMK reactor uses water just for cooling and graphite for moderation. So when there is no water or the water boils and produces voids and the the heat and reactivity rise. This causes reactivity to continue to rise, heat and thus steam production increases so more voids and it produces a feedback loop that allows for a runaway reaction and a meltdown.
In a reactor with a positive void coefficient voids from no water or water bubbles speeds up the reaction. In a reactor with a negative void coefficient no water or air bubbles (voids) slow and stop the reaction.
I think I did OK with the graphite tipped control rods, but to be clear graphite is a moderator so it increases the reaction. Higher up the RBMK reactors control rods were made of boron which is a neutron absorber used to slow and stop the fission reaction. By having SLOW moving control rods with graphite tips (graphite is a moderator that speeds up the reaction) before the boron parts get down in between the fuel rods to stop the reaction it gave the reaction enough boost to push it over the edge and produce a runaway reaction at Chernobyl.
Both of the attributes made the reactors rely much more hevily on humans doing the right thing. With a western reactor Homer Simpson didn't even cuase a China Syndrome emergency.
There is a follow up question: why did the Soviets use RBMK reactors? They were cheaper, quicker and easier to produce with high electrical production, they allowed for plutonium production and they allowed for refueling during operation so reduced time offline.
Posted on 4/27/26 at 5:03 am to rt3
Az5 button. "We didn't do anything wrong"
Posted on 4/27/26 at 5:34 am to rt3
Oddly enough, watching that show helped to educate me on nuclear power and how safe it is. I read a lot more about it after the show, and that knowledge actually gave me the confidence that nuclear power is very safe. Once I understood it, it wasn’t so scary.
Posted on 4/27/26 at 5:41 am to PrimeTime Money
Yeah, I think it's past time we make a push in this country to expand nuclear.
Posted on 4/27/26 at 6:10 am to rt3
Jared Harris (Legasov) and Paul Ritter (Dyatlov) absolutely nailed their roles
Posted on 4/27/26 at 8:02 am to Obtuse1
quote:
The reactor had boron control rods used to control reactivity. When scram was initiated the control rods would be lowered down into the core to basically shut down the nuclear reaction. The problem was the control rods had large graphite tips. So during the scram the the tips went in first but unlike the boron which produces a negative scram (slowing and stoping the fission reaction) the graphite produces a positive scram where the reaction speeds up VERY quickly.
The narrative said that the rods jammed as they were inserted. I can see, from your explanation, that this would result in positive SCRAM because the graphite tips would be reacting but not the boron? But why did they jam?
Posted on 4/27/26 at 8:19 am to WestCoastAg
I have this gif on my phone. It gets a lot of use.
Posted on 4/27/26 at 8:23 am to UKWildcats
quote:
I think it's past time we make a push in this country to expand nuclear.
The left will never allow it...it solves the "green energy problem" too well. They need their trojan horse solutions to continue advancing the rest of their ideology.
Posted on 4/27/26 at 8:31 am to Obtuse1
Great input, thanks Obtuse.
What was the purpose of making the tips out of graphite? I get confused when you use the term “moderator”. Does a moderator slow down or speed up the reaction and thus the temperature? Why not just make the rods completely out of boron?
quote:
I think I did OK with the graphite tipped control rods, but to be clear graphite is a moderator so it increases the reaction. Higher up the RBMK reactors control rods were made of boron which is a neutron absorber used to slow and stop the fission reaction.
What was the purpose of making the tips out of graphite? I get confused when you use the term “moderator”. Does a moderator slow down or speed up the reaction and thus the temperature? Why not just make the rods completely out of boron?
This post was edited on 4/27/26 at 8:32 am
Posted on 4/27/26 at 8:35 am to rt3
quote:
Chernobyl
By Soviet standards at the time, the core was essentially housed in a tin shed...
Posted on 4/27/26 at 8:41 am to Jimbeaux
quote:
Does a moderator slow down or speed up the reaction
I think it moderates the speed of the neutrons, thus increasing the chance of collisions and boosting the reaction?
Posted on 4/27/26 at 9:16 am to rt3
I heard that the radiation was so intense that you could get radioactive particles from watching a video of the incident
Posted on 4/27/26 at 9:16 am to Penrod
quote:
Obtuse1
Thanks for sharing this. I found it easy to follow and fascinating. Stuff like this is why I love this forum.
Chernobyl is an amazing show. It did a fantastic job of making me feel the fear that those experiencing this disaster felt at that time while also remaining true enough to the original history (and simultaneously being entertaining and easy to follow).
I had no idea Paul Ritter passed away from brain cancer. RIP to an awesome actor who spawned a fantastic meme.
Posted on 4/27/26 at 9:22 am to PrimeTime Money
quote:
Oddly enough, watching that show helped to educate me on nuclear power and how safe it is. I read a lot more about it after the show, and that knowledge actually gave me the confidence that nuclear power is very safe. Once I understood it, it wasn’t so scary.
We should all laugh at Germany. They (Merkel) shut down their reactors and became more reliant on coal and Russian natural gas, with increased energy costs to boot. Meanwhile France is the nuclear gigachad.
From Google:
- Capacity & Output: As of 2026, France operates 57 reactors across 19 plants, providing approximately 63 GWe of capacity.
- Energy Mix: Nuclear accounts for roughly 70% of domestic electricity production, making it the highest proportion globally.
- Economic Impact: The industry supports over 200,000 jobs and generates over €3 billion per year in export revenue.
- Future Strategy: Despite previous plans to reduce nuclear reliance, France committed in 2022 to building six new EPR reactors, with plans for an additional eight.
- Fuel Recycling: About 17% of France's electricity is generated from recycled nuclear fuel.
- Low Carbon: Due to high nuclear usage, France has some of the lowest per-capita carbon dioxide emissions in the EU.
Posted on 4/27/26 at 3:52 pm to Jimbeaux
quote:
I get confused when you use the term “moderator”. Does a moderator slow down or speed up the reaction and thus the temperature?
The word moderator in a nuclear reactor is indeed counterintuitive. One would think a moderator would slow the reaction, but it does the opposite. It actually moderates (reduces) the speed of the neutrons released by the fission in the core. Again intuitively, one would think slowing the neutrons would slow the reaction, but it does the opposite. By slowing the fast neutrons down to slow AKA thermal neutrons you significantly increase the chance they with strike another Uranium atom and "split" it, releasing more neutrons and continuing the chain reaction.
quote:
Why not just make the rods completely out of boron?
That seems to be the answer, right?
The short answer is that Russia used graphite tips or "followers" to increase the fuel efficiency of the reactor. When you use water (particularly light water vs heavy water) as a moderator, it reduces efficiency because while it is a moderator, it is also a neutron absorber. So while it slows neutrons, increasing reactivity, it also absorbs some making it not as efficient as graphite. So the question is why not have seperate boron and graphite rods? The simple answer seems to be it produces a less complex reactor and prevents you from ever having the brakes fully engaged and the accelerator to the floor (if you will excuse the car analogy).
RBMK reactors were cheap to build and fuel efficient like a Lada (shitty Russian car) and COULD be operated safely but they had a lower safety margin than Western reactor designs and it required the operators to understand the science at least better than Homer Simpson. It also requires a system where anyone in the room can stop the "line" an idea incongruent with Soviet thinking at the time. If someone 1000km away in Moscow says there will be a safety test tonight there WILL be a safety test tonight. The fear of Moscow was higher than the fear of a runaway reaction partly because they knew the chance of an "explosion" from Moscow was 100% and the chance of an explosion in the plant was at least slightly lower.
Posted on 4/27/26 at 4:00 pm to Indefatigable
quote:
Bruh, linking a 1 hour video? Lol
Bruh, you have free will.
Posted on 4/27/26 at 4:07 pm to Hangover Haven
quote:
By Soviet standards at the time, the core was essentially housed in a tin shed...
That is another advantage of the RBMK reactor design: you don't need a huge pressure vessel or heavy containment building. However, if shite goes sideways and you end up with an elephant foot, you have to build a $2 billion containment structure. Fun fact the NSC (new containment structure) is the largest land-based movable structure man has ever made. Russia, being Russia, they just keep trying to make Chernobyl the gift that keeps on giving when last year they flew a drone into the NSC in the war against Ukraine.
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