I apologize if I have misinformation, but after watching Chernobyl and doing no more research than a few web searches, it seems that the late Soviet Union was weirdly fixated on NOT fixing the RBMK reactor design. This went to the point of making sure nobody knew there was a flaw even if it meant, y’know, continuing to use potentially-crippled safety systems.
Obviously, there were big issues with the later-era USSR governance. And the mid-era governance, the early-era governance… and yet. I don’t understand why this was such an issue. Sure, the reactor design was flawed, but it was also something like 30 years old, right? Why would a hypothetical flaw that could be documented and avoided, and probably fixed in a realistic timeframe be so sensitive? Soviet/Russian engineering in general was not against fixing problems. For example, the T-34 tank or AK-47 rifle were not exactly great in the first released models, but both were polished over time. It’s not as if they had to wave a banner declaring a huge mistake in front of the West, either.
I know that sometimes ego and stupidity get in the way of good engineering, but in this case the problem was absolutely known, but everyone involved went out of their way to ignore it. Is there a clear understanding as to why?
It was a very inexpensive reactor to build and run. IIRC the reactor did not need highly enriched uranium (or even enriched at all…not sure) and could use regular water instead of heavy water.
And the flaw was not really obvious. It took a weird sequence of events. The operators working at the time knew their stuff pretty well, some even pushed back, but the real flaw was the Soviet system that didn’t allow underlings much room to say no.
They thought the downsides could be managed. Mostly they were but like someone once said to me about owning lions, you only get one mistake.
Read e.g. the section of report starting at page 16, or section 5.2. starting down page 17, or section 5.2.3. starting on page 19.
Lack of safety culture is so insidious. You see it even in modern Western nuclear plants (even when they are safe). It’s the attitude when people think “well, this works, what’s the problem?”, not “hmmm, I wonder if this can be unsafe?”
The HBO series is primarily about the social and political reasons for the disaster, more so than the technical, although it does a great job at that as well. Still, the show’s premise is that lies and secrecy in the face of facts are counterproductive and dangerous. You do not question the State, because the State is always right, even when it’s wrong. It’s a warning about blind loyalty to authority and how that can literally blow up in your face when that authority is playing fast and loose with the truth. Something not limited only to the Soviet Union for sure. In this case, it’s all about saving face, which seems to be both an external and internal struggle. Not only did the powers that be not want to appear flawed to the outside, they couldn’t admit it to themselves either, so they deny deny deny. The mentioned lack of safety culture and political dogma would likely also lead to an attitude of this being an isolated incident caused by a very specific set of unlikely circumstances. So just tweak the procedures to make sure this specific incident doesn’t happen again, done and dusted.
On a more technical level I’ve read about two solutions to mitigate the design problems. The simplest option was de-rating the reactor output so it wasn’t as close to its design limit and more able to handle unusual conditions. The number I have in my head is a 10-20% reduction. However, these being very powerful plants means that’s a significant cut to the grid’s capacity, which in most of the Soviet Union was already suffering from electricity shortages. At Chernobyl, the four reactors provided 10% of Ukraine’s power, and with one reactor out of commission, representing a loss of 2.5% of the entire grid’s capacity, de-rating just the other three reactors at that one plant would reduce the national grid another 1.5%. I can certainly see them being reluctant to implement those reductions, especially in the short term before any new plants could be brought online.
Another option, and I don’t know if this was ever done, was to modify the control rod design to eliminate the water pockets at the top and bottom of the graphite accelerators (tips in the HBO series). Look up the VlogBrothers’ and Scott Manley’s videos on YouTube for an explanation of how these aren’t tips but integral components nearly as long as the neutron-absorbing parts of the rods. The trouble is that the reactor was designed for a specific height of control rod, and making them longer is not trivial. It’s like finding a flaw in your car design, which has been in production for years already, and the fix is to make the axles 6" wider. That’s a very expensive fix at best, if it’s even possible at all. I think in this case they instead opted for more procedural changes to ensure that they can’t pull out nearly as many control rods as they did at Chernobyl.
The IAEA report describes safety modifications that were implemented after the disaster, including, naturally, modification of the control rods to eliminate water columns at the bottom.
My presumption is that nobody, reluctant or not, was going to (be allowed to) do nothing but implement “procedural changes” after the Chernobyl clusterfuck, especially since a bunch of those reactors are still in operation, including to this very day. Not that this implies RBMK reactors, or any similar vintage design, are now as safe as a latest-gen nuclear reactor would be, but at least the immediate triggers leading to the accident have been ameliorated.
It would be interesting to read about current safety culture (or lack thereof) compared to that at the time of the accident.
I haven’t seen the miniseries but this thread reminds me of something I once read about the Chernobyl disaster. It was that one of the steps the Soviet government took immediately after radioactive material was released was to begin seeding clouds in the area. The goal was to make it rain so the radioactive material in the atmosphere would be deposited in Ukraine rather than being carried east with the wind into Russia.
I only saw this mentioned in one source. Can anyone confirm whether or not it happened?
To be sure the RBMK reactor has some dangerous quirks. The thing is, we know about its quirks.
But Murphy’s Law tells us if there is a way for it to go wrong it will go wrong. And it did. Eventually, given enough time, enough screw-ups happen that we can expect something like this.
The real problem at Chernobyl was not the reactor design but the culture that the employees worked in.
I have watched way too many airplane accident shows and a common theme in many (not all) accidents was communication failure in the cockpit. Because of that regulations and training have been adjusted to allow junior members of the flight crew to be heard and taken seriously.
At Chernobyl you had one guy in charge not listening to his subordinates because he was under pressure to get a test done…no matter what. In his zeal to make it happen safety measures were circumvented and he did not listen when others told him they should not do what they were doing.
Add in the fundamental wackiness of that reactor and boom.
But remember, there are lots of these reactors out there and they have been running fine for decades (indeed…Chernobyl kept up operating their other reactors long after the explosion).