mersenneforum.org Chernobyl -Fred Pohl
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 2021-02-25, 23:49 #12 Batalov     "Serge" Mar 2008 Phi(4,2^7658614+1)/2 9,391 Posts I remember that we had the first wave of the series' impressions; I will not repeat what I wrote there. In short, it was heart-touchingly accurate (I'd lived in those times, though not in Chernobyl; I've been to a Chernobyl twin sister town, too). The bus was accurate (Ukrainian bus assembly, they composited dozens of the same (real) bus into the landscape); we had this make of buses in central Russia too. The whole setting is very smartly chosen - it is yet another twin sister station in Lithuania iirc. It is a remarkable series. Character development is outstanding; the characters don't look like cardboard cutouts. The actors were brilliant. Accuracy and mise-en-scene details are strikingly good. Maybe we should merge those two discussion threads. (this thread predates the series by years; it was about a book!)
2021-02-26, 00:10   #13
storm5510
Random Account

Aug 2009

19×101 Posts

Quote:
 Originally Posted by tServo The reactor normally produced 3,200 megawatts thermal energy as steam to produce 1,000 megawatts of electric power. At the instant the reactor blew up ( explosion #1) it was producing at least over 10 times that, about 32,000 to 35,000 megawatts. Some estimates say it was 120 times normal max power. storm5510, since you just saw it do you remember the figure? Of course, the instruments that measured the power may not have the range to go high enough or might be too slow to give a final reading. Can anyone convert this amount of thermal energy to equivalent megatons of explosive energy? Explosion #1 was the one that blew the 1000 ton lid off the reactor, exposing the core to the atmosphere. The core then reacted with the air to produce hydrogen which caused explosion #2.
Valery Legasov, played by Jared Harris, stated in the trial, either "32,000" or "over 32,000," I do not remember his exact wording.

In recent years, I have seen two different actors play Anatoly Dyatlov. Both portrayed him as having extreme hubris. During his career, he received two large doses of radiation. The first while installing reactors in submarines, and the second at Chernobyl. With all that, he managed to live until December of 1995.

Question: Why are thermal energy units expressed at "megawatts?" If this is heat, then Kelvin or Celsius might be easier to comprehend.

2021-02-26, 13:26   #14
Dr Sardonicus

Feb 2017
Nowhere

2×7×11×29 Posts

Quote:
 Originally Posted by tServo The reactor normally produced 3,200 megawatts thermal energy as steam to produce 1,000 megawatts of electric power. At the instant the reactor blew up ( explosion #1) it was producing at least over 10 times that, about 32,000 to 35,000 megawatts. Some estimates say it was 120 times normal max power. storm5510, since you just saw it do you remember the figure? Of course, the instruments that measured the power may not have the range to go high enough or might be too slow to give a final reading. Can anyone convert this amount of thermal energy to equivalent megatons of explosive energy? Explosion #1 was the one that blew the 1000 ton lid off the reactor, exposing the core to the atmosphere. The core then reacted with the air to produce hydrogen which caused explosion #2.
I tried to find out how much power a slug of corium produces, without much success. I read that a lot of the heat is produced by the radioactive decay of short-lived isotopes. When the stuff hits water, a number of interesting chemical reactions are likely to ensue (zirconium grabs the oxygen from water molecules and releases hydrogen gas, for example).

I did however notice that temperature estimates were fairly consistent, somewhat above 2000 C. I had some idea of how big the slug of magma was, but wasn't sure what to do next.

Then, I recalled from physics that there is a formula for power that depends only on temperature - the power radiated per unit area of a "perfect blackbody." The Stefan-Boltzmann Law says

$\frac{P}{A}\;=\;\sigma T^{4}$

that is, the power per unit area is proportional to the fourth power of the absolute temperature. For a BOTE calculation I'll treat the slug of magma as a perfect blackbody, take A = 10 m^2, T = 2500 K, and the known value 5.6703 x 10-8 W/m^2/T^4. (For a less-than-perfect blackbody, there is a fudge factor called the "emissivity," which is between 0 and 1.)

The above gives P = 22 megawatts, or 2.2 x 107 J/sec, approximately. That would be enough to vaporize almost a ton 10 kg of water per second - if it could transfer the heat to the water that fast, which I'm pretty sure it couldn't.

A kiloton is about 4.184 x 10^12 J

Last fiddled with by Dr Sardonicus on 2021-02-28 at 15:31 Reason: As indicated. Lost a factor of 100 somewhere...

 2021-02-27, 10:14 #15 LaurV Romulan Interpreter     Jun 2011 Thailand 937710 Posts re: hiroshima vs nagasaki bombs, we recently started following a Spanish (team?) youtuber as we ran into their "comparative" videos which we liked. One of them debates exactly this, the two bombs being actually... small, by comparison. Last fiddled with by LaurV on 2021-02-27 at 10:15
2021-02-28, 02:47   #16
tServo

"Marv"
May 2009
near the Tannhäuser Gate

54 Posts

Quote:
 Originally Posted by LaurV re: hiroshima vs nagasaki bombs, we recently started following a Spanish (team?) youtuber as we ran into their "comparative" videos which we liked. One of them debates exactly this, the two bombs being actually... small, by comparison.
They measure explosions by height?
Granted, you can make your presentation anyway you want but that still seems odd.

 2021-03-23, 06:49 #17 LaurV Romulan Interpreter     Jun 2011 Thailand 9,377 Posts Indeed, if you think about, you are right it is odd, but initially I didn't think about, I assumed it is kinda radius, or, if you take the wind into account, spreading area, whatever. We are not explosion experts (and the guys who made the videos are neither).
2021-03-23, 13:03   #18
Xyzzy

"Mike"
Aug 2002

5·1,609 Posts

We don't remember why they are measured by height, but we do know that is how it is done. In a previous life we attended a military school to learn about nuclear and chemical weapons. One of the main things we studied was how to do downwind hazard predictions and how to calculate yield. This was almost 30 years ago so we don't remember much.

Attached Files
 NBC_Field_Handbook.pdf (7.09 MB, 7 views)

2021-03-23, 13:54   #19
Dr Sardonicus

Feb 2017
Nowhere

2×7×11×29 Posts

Quote:
 Originally Posted by Xyzzy We don't remember why they are measured by height, but we do know that is how it is done. In a previous life we attended a military school to learn about nuclear and chemical weapons. One of the main things we studied was how to do downwind hazard predictions and how to calculate yield. This was almost 30 years ago so we don't remember much.
My guess: The bigger the explosion, the bigger the fireball. The bigger the fireball, the higher it rises before "mushrooming out." Of course, if the fireball is big enough, it can hit the tropopause, which is like hitting a lid. The effect is seen in the "anvil tops" of thunderstorm clouds.

2021-03-23, 15:02   #20
Nick

Dec 2012
The Netherlands

2·829 Posts

Quote:
 Originally Posted by Xyzzy In a previous life we attended a military school to learn about nuclear and chemical weapons.
The Big Bus safety briefing

2021-03-23, 17:05   #21
storm5510
Random Account

Aug 2009

19×101 Posts

Quote:
 Originally Posted by tServo ...storm5510, since you just saw it do you remember the figure?...
I watched some of the trial on YouTube recently. He said, "Over 33,000."

After watching the series for the first time, I was curious about where it had been filmed. Latvia, as it turned out. Naturally, the buildings and landscape were not exact. All that was really necessary was to put a mock-up of the red and white exhaust tower on top of a similar building. Everything else fell into place.