Saturday, May 18, 2019


There's a new HBO drama about the core breach and fire at Chernobyl. The 2nd episode became available today. Here's the trailer.

YouTube will provide you with all the documentaries and information you could possibly watch but this drama makes it real.

Here is the story you need hear. There were huge water tanks under the reactor. They needed to be emptied before the core melted through and contacted them. If that had happened, the resulting explosion would have been between 3 and 5 megatons. Megatons. Remember the Hiroshima bomb was 20 kilotons**. It would have torn open the other reactors at the site and dispersed enough radiation to make the western Soviet Union and most of Europe uninhabitable.

Three men volunteered to enter the flooded basement under the burning reactor to find and open the valves. They succeeded. They took high doses of radiation and some reports suggest they died but from what I can find it appears they survived the initial period of acute radiation sickness.

Their names were Alexei Ananenko, Valeri Bespalov and Boris Baranov. They saved millions of lives and a continent.

UPDATE: In the comments, the physics and math question of the potential size of the explosion is generating some thoughtful questions. It may be like the old game of "telephone", where the actual risk was of the steam explosion ejecting the core material into the atmosphere along with all the radioactive water, resulting in a down wind radiation fallout equivalent to a 3-5 megaton bomb. If it had done that as well at causing the other reactors to fail, the outcome would would have been bad enough. I am genuinely curious now and want to understand. If I find a definitive answer, I'll post it.

**Edited to correct yield per Old 1811


Ratus said...

"...explosion would have been between 3 and 5 megatons..."

Wait wut? Seriously?

How is that possible, the uranium isn't enriched enough. 3-4% not the 90% of an actual device.

Beans said...

Ratus, I think they mean by the rather extreme ultra-high temp/pressure steam explosion that would have resulted if the cores had dropped into that much water.

Instant heating and expansion of that much water contained in an underground storage container, which would have held the pressure in, until, well, think of over heating a pressure cooker with a stuck relief valve. Except a pressure cooker the size of maybe 3 high school gyms full of water, with a radioactive heat source on fire?

Super massive dirty bomb explosion. Would make a MOAB look like a handheld firecracker.

The limited steam explosion from water from the cooling system was enough to blow a 4 million pound lid off the system. That's without the water from the tanks below it. With full tanks, yeah, it would have been, well, a 3-4 Megaton equivalent explosion.

Live steam (steam at extreme pressures and temperatures) is far more deadly than people understand. Or want to understand. In a lot of ways, the world is a safer place without high pressure steam power anywhere near populated areas.

We, the world, lucked out that day because of those 3 brave men, and the rest of the reactor staff that stayed and died at their stations.

Beans said...

Oh, and Borepatch?

Thanks for the nightmares. Geez, my overactive imagination just did a full play of the whole system going through that steam explosion.

Dagnabit, gonna hafta watch some Hallmark movies to clean my brain over that.

Ratus said...

Nope, it was the first smaller explosion that knock off the 1000 ton/2 million pound lid.

The second bigger explosion estimated at around 10 tons of TNT that dispersed the estimated 1200 tons of reactor fuel and graphite.

But you are trying to tell me that I can easily get the equivalent of a multi Megatron nuclear weapon by just dropping a super heated mass into a contained pool of water?

Even if this is possible and the results are just in the multi kiloton range, everything needed is entirely legal and readily available.

Directrix Gazer said...

The steam explosion could have spread a great deal of contaminated material over a vast area, killing many people. These men are unquestionably heroes.

However, I am profoundly suspicious of the claim of a multi-megaton nuclear explosion, indeed any nuclear explosion, being averted. A nuclear initiation cannot be triggered by simply piling up a heap of fissile material, much less low-enriched material, and the pressure Beans talks about in his response still many orders of magnitude too low to permit even a low-order initiation.

This question of bringing all the material together in just the right geometry with just the right timing is the central problem of nuclear weapons design. Even the slightest deviation from perfection leads to the core being blown apart while releasing only a tiny, tiny fraction of its designed yield, a phenomenon known as a "squib."

I suspect that this claim has resulted from a multi-decade game of telephone following an originally garbled translation. The original statement was likely something like: "fallout equivalent to the detonation of a 3-5 megaton nuclear bomb." After someone nontechnical left out the important qualifier in their translation, another person helpfully looked up how destructive the blast from such a bomb would be and added it as additional information, after which yet another person mixed that information into the original quote.

Ratus said...

This is what I'm thinking too.

The enrichment was only 2% at the time of the incident, they raised it to between 3-4% to prevent other reactors of the same model from having the same type of event.

talnik said...

Now I won't have to see the next episode.

Old 1811 said...

Are you sure you got the math right? Isn't 20,000 kilotons 20 megatons?

Borepatch said...

Beans, this was from ASM826, not from me. Credit where it's due.


Beans said...

BP - I'm blaming the messenger :)

Old NFO said...

If ALL FOUR of the reactors had gone off, which was a possibility if #4 melted down into the water reservoir and the massive steam explosion caused failures of the other three containments, I believed the low end of 3 megatons was possible. I do remember NEST doing some research into that back in the late 80s.

Ken said...

As a former nuclear weapons specialist I doubt that a steam explosion could result in energy release in the megaton range.

danielbarger said...

The truth of the matter is we simply do not know exactly how much energy would be released in such a situation. But it's not going to be measured in MegaTons. The VERY HOT CORE dropping into the water tanks would have turned much of that water to steam.....and that steam would have expanded at an amazing rate. Water is about 1800 times more dense than steam so all that water would have expanded to a volume 1800 times of the original in a matter of a second or so. That's a LOT of energy....but not equal to a million tons of TNT. The result would have contaminated far more area than was contaminated by the explosion. But it would not be an
area the size of eastern Europe. Still....such a steam explosion would have been a very bad thing and the men who prevented it were heroic....and perhaps a bit crazy.