Chernobyl steam / thermal explosion...

[Archibald]

... was vastly overblown in the show (megaton explosion WTF ??!!). BUT they did not invented that mistake out of thin air: it was mentionned long before the series - well even at the time of the disaster since they send that "suicide squad" closing the vanes and emptying the pool of water.

Now, a non-megaton, non-nuclear explosion far less powerful could have happened. But what kind of yield then ?

How large would the steam explosion at Chernobyl have been?

So the second episode of the HBO series began to cover the risk of a steam explosion that led to them sending three divers into the water below the reactor to drain the tanks. This occurred after ...

physics.stackexchange.com

Ok then: 0.15 to 4 kt of TNT...

Well, this not a megaton by a very long shot, and it is not a nuclear explosion by any mean. YET - the yield remain pretty scary if compared to the largest non-nuclear explosions in history.

Largest artificial non-nuclear explosions - Wikipedia

en.wikipedia.org

0.15 kt put it at Beirut level.

4 kt - frack, larger than freakkin' Halifax.

Even at 0.15 Kt only - 150 metric tons of TNT equivalent - we certainly agree it wouldn't do any good to the burning nuclear reactor nor to the three others in its immediate surroundings...

So yes, they probably dodged a bullet there. Basically, adding a "Beirut" on top of OTL horror...

What do you think ? Are the first link calculations valid ?

 

[Fencer]

 

[dannydale]

Vichnaya Pamyat.

 

[Scott Kenny]

What do you think ? Are the first link calculations valid ?

They appear to be. I went all the way down to the last one, the dude writing up a basic steam explosion. How much energy is contained in a mass of water flash-heated to steam.

So evaporating 1000 kg of water, with initial temperature of 25 C yields.
Q=1000∗(4.8∗75+2260)=2.6⋅10E9J
Knowing that 1 ton TNT is equivalent to 4.18⋅10E9J, yields 0.5 tons of TNT.

(added exponent markers since the superscripts didn't carry over in the copy-paste)

However. That equation doesn't actually math the way the answer given says it does.

I think it's supposed to have the mass of the water in grams, not kg, because the specific heat of water and latent heat of vaporization of water are given per gram.

And he's got a typo in the specific heat, it's 4.18 not 4.8.



Fixing all that gives us

So evaporating 1000 kg of water, with initial temperature of 25 C yields.
Q=1,000,000∗(4.18∗75+2260)=2.57⋅10E9J
Knowing that 1 ton TNT is equivalent to 4.18⋅10E9J, yields 0.615 tons of TNT per ton of water flashing into steam

Now. This also involves not just the amount of water in the core. We're talking the entire quantity of water in the entire primary loop. 33,000 liters (33 tons) in the core. 2000 tons in the clean condensate tank. Several hundred tons in the steam separators. And finally several thousand tons in the main circulation loop. At least 5000 tons of water. And all of that is flashing to steam at once.

This puts the total steam-explosion yield a minimum of 3 kilotons.

One hell of a big boom. 3x the force of the 2020 Beirut disaster(!).

 

[Archibald]

Thanks for the calculations. Shit, hell of a blast, close from Halifax 1917.
Would have done no good to reactors 1,2 and 3.