The 1975 Leningrad Nuclear Accident: The Road to Chernobyl

Just under eleven years before Chernobyl exploded and contaminated swathes of Eastern Europe, we turn our attention far north to the very first reactor of the Leningrad Nuclear Power Plant. On November 30th, 1975, this reactor would suffer an accident that came frighteningly close to causing its complete destruction. This is the story of the Leningrad Chernobyl, from inside the Control Room, and inside the reactor core.

Chapters:

00:00: Introduction
00:31: A Difficult Year
03:41: A Fatal Mistake
04:51: Fighting the Xenon Pit
07:53: The Impossible
11:14: Channel 13-33
14:48: Cover Up
16:43: The Leningrad Chernobyl

Thank you to Bobby and Sredmash for assisting in the writing of this script :)

[YouveBeenMiddled]

When you're actively overriding multiple automatic protections in a radioactive system, you should probably stop and rethink your plan.

[oscarr.g.]

One of the things that amazed me after discovering this channel and following some of the recommended readings you have given across your videos was realizing how exhausting for the operators, both physically and mentally, was to work on the control panel of one of these behemoths to keep everything under control. And of course once more, hats off to you sir !

[michielhuygelier]

i have a hunch that somewhere in the deepest archive room of the kremlin there are documents that accurately describe the behavior of these reactor in all working conditions.

[otrab]

Imagine testing in production with an RBMK reactor. That was basically what was happening at Leningrad unit 1.

[fred]

I can't pretend to understand these accidents but I try very hard to. Thank you for breaking it all down

[dez]

It baffles me how you are able to read all of those reports! Long, dry, and boring as hell. Yet you read all of them, and you are able to make sense of it all. Thank you on behalf of us all. You actually make it understandable and interesting. I salute you! Teaching seems to be your calling! I truly appreciate all of what you do.

[SlavicGaming]

TCG I have watched you since the original iceberg videos, I wanna thank you for you boosting my interest in the Chernobyl Disaster and RBMK Reactors in general.

[erikziak]

Could you also do a video about the Jaslovské Bohunice A1 incidents, the 2nd one resulting in partially melting the core? The reactor was an experimental of the type KS-150 and was working with natural (not enriched) uranium and the plant had a rather low power output of 104 MWe. Moderator was heavy water and coolant was gaseous carbon dioxide. The reactor was designed to be refueled while in operation and both incidents happened during refueling of a critical reactor. The first accident due to operator error combined with bad design of the locking mechanism of the fuel assembly and the second, that led to partial meltdown, was caused again by operator error as they unintentionally teared a sack containing silica gel balls and did not properly clean the channels. Which resulted in low coolant gas flow and overheating and rupturing the fuel channel and its surrounding channels too. While it was technically possible to repair the reactor, it was not feasible from an economical point, as new, more powerful soviet VVER 440/V230 reactors were being build on the site as part of the V1 plant, which operated without any incidents from 1978/1980 to 2006/2008 (block 1 and block 2). The two currently running VVER 440/V213, which have been modernized and their thermal power risen by 7% from 1375 MWt to 1471 MWt together with improvements in the generator part (power output increase by again by 7% from 472 MWe to 505 MWe), are scheduled to be shut down in 2065 after 81/80 years if operation (block 1/2). A new 1200 MWe block is being mentioned quite often in the last years, according to plans the construction should begin 2035 and commercial operation start in 2045. The new V3 plant should be running until 2125. Wow. Nuclear reactors and power plants are build to last...

[deaddropholiday]

Have you read the English translation of Chernousenko's "Chernobyl: Insight From the Inside"? It has some illuminating information about this model of reactor which I haven't seen anywhere else. There were a number of YouTube interviews of Chernousenko before he passed away but they seem to have disappeared into the ether. Very interesting character who landed himself in a whole heap of trouble over his criticisms. I was particularly interested in a very short passage where he said - rather enigmatically - that they were so concerned about the threat of seasonal rain flooding the reactor basement and causing a flashover they redirected weather fronts away from the facility ....

[TiagoJoaoSilva]

wait a minute! Did the Leningrad accident provide the USSR and Legasov with a ready-made sequence of events they could massage and apply to Chornobyl?

[TacticalOni]

Oh shit I havent been this early since my first day on the job. Great video TCG!

[robertliskey]

Another good presentation. It stirred my memory they sure knew about PWR reactors, after all it was not an RBMK in K-19 that was in the Kennedy era! Apparently they could not cool that one even with the rods in. Makes you wonder. Keep up the wonderful work!

[DackelDelay]

subscribed just a few mins in; one can tell when there is substantial knowledge to be gained ;)

just one thing tho: please consider investing in a better mic. can't really put my finger on it, but the audio is kinda flat/noisy. either way, great content!

[patrikmajkowski]

The level of detail in your videos is amazing

[MarijnRoorda]

In the end though, the reason for both accidents was the state and its institutions. Of course, one couldn't say that back then, the state was infallible! And therein lies the primary issue.

[ON-O]

Another case study in: Commies cannot boil water

[Stubbies]

The shorter graphite for the control rods makes perfect sense for the differing outcomes between Leningrad and Chernobyl. With Leningrad those longer graphite portions were already displacing more water thus AZ-5 doesn't cause as big of a spike since graphite was already in play. At Chernobyl where it goes from neutron absorbing water to neutron enhancing graphite the spike is much larger because of the fact that it was already getting out of control even with the water slowing things up. Shortly after AZ-5 is pushed and the flip in reactivity occurs between water and graphite that was all it needed to really go over the top on reactivity thanks to the positive void coefficient combined with that shorter control rod graphite portion.

[tunneloflight]

... they created a bizarre unstable buckling condition too ... Under those conditions, ring oscillations can set in.

[mikeall]

Great research! One comment for those who don't know... the reason increasing fuel enrichment can help reduce the chances of an accident like this is because when the enrichment increases, the fuel designers can put more "burnable poisons" into the pellets. This allows for better transient characteristics.

Then as the fuel burns, natural poisons build up as the burnable ones burn out and the fuel is consumed. There is some complicatedness to this balance because boiling water reactors produce a descent amount of plutonium, towards the back 3rd or sonof it's lifespan.

Thus when western BWRs are at the end of a fuel cycle, the core fuel limits have the lowest margin, since the control rods are full out.

Im not familiar enough with the RBMK design to comment on how that later is impacted, but I fission works the same, even in Russia.

[alder]

I’ve recently discovered your channel and after binge-watching most of your videos I’m beyond amazement due to the quality and details of your work. Your channel is something that I needed to find. It’s still very confusing to me and all those conflicting quotes, different institutions and names saying different things make a big mess in my head, but I’m very slowly beginning to understand more and more thanks to your efforts.