Anyone watching the Chernobyl miniseries on HBO?

[OVERKILL]

Originally Posted by dailydriver
Addicted to this series!

There was so much cover-up (by the Soviets/KGB) shrouding what actually happened when it was a current event that it is enlightening (but VERY dark despairing) to finally get some truth on the whole disaster.

"Black eye" to the whole industry, or not, the warnings the facts of this incident bring to light, had BETTER BE heeded going forward (YES even with our 'superior' and now much updated technology, and much more conscientious and fastidious plant workers.)!

If you read the report I linked (and I highly suggest doing so for a more analytical account of the events that haven't been sensationalized for your "viewing pleasure"), the design itself was not failure-tolerant. Basically, the safety of the plant hinged on operation and avoiding failure, there was very little in terms of provisions or protection if things DID go wrong. And of course they did. Plants in the rest of the world had containment and other disaster mitigation measures for the unlikely event of things going wrong. The events that transpired at Chernobyl were essentially impossible at the units operated elsewhere, because they were not of that style. The Soviets were aware of the risks of the design, and its lack of containment, which is why it was being phased out.

Now obviously lack of cooling incidents can still cause a meltdown in other reactor types like the LWR (Fukushima, Three-Mile Island) but the resulting incident is not on the same scale. Other reactor types like the CANDU are essentially immune, which is also covered in that paper.

 

[dave1251]

I've been forced to learn more about Chernobyl then I thought I would learn for professional reasons. What the Soviet government did to cover up and clean up was criminal.

 

[mk378]

The Chernobyl explosion and subsequent meltdown initiated from sudden over-reactivity, not loss of cooling. It is the only large plant to ever fail that way. At Three Mile Island and Fukushima, the fission reactions had been successfully stopped early in the incident, but there was inability to remove decay heat from the core resulting in melting hours to days later.

The tendency to over-react was fundamentally a design issue, but also the operators were not fully knowledgeable of the limitations of the design and that night operated Chernobyl at conditions that made it unstable.

The Chernobyl type plant's graphite moderation had long been considered an unacceptable fire risk by Western engineers. At the time only a very few graphite moderated power plants remained operational other than those in the USSR.

 

[OVERKILL]

Originally Posted by mk378
The Chernobyl explosion and subsequent meltdown initiated from sudden over-reactivity, not loss of cooling. It is the only large plant to ever fail that way. At Three Mile Island and Fukushima, the fission reactions had been successfully stopped early in the incident, but there was inability to remove decay heat from the core resulting in melting hours to days later.

The tendency to over-react was fundamentally a design issue, but also the operators were not fully knowledgeable of the limitations of the design and that night operated Chernobyl at conditions that made it unstable.

The Chernobyl type plant's graphite moderation had long been considered an unacceptable fire risk by Western engineers. At the time only a very few graphite moderated power plants remained operational other than those in the USSR.


Basically. If you read the report from AECL, the sequence of events that resulted in the over-reactivity and massive power spike stemmed from user error and the design of the control system. Essentially:

- The reactor was lowered to 50% power, and run there for quite a period. This was initially done in preparation for the test, but demand prevented the test from proceeding when it was supposed to
- There was a ton of pressure on them to complete the test due to the refuelling schedule and if it wasn't completed this go-round, it would have to wait an entire year
- Once preparation for the test commenced, one of the power controls was improperly set and power dropped well past the target, to around 2%. This was NOT on purpose, and far lower than it was supposed to go
- The resultant almost complete shutdown of the reactor resulted in significant xenon poisoning, further hindering the operator's attempts to bring the reactor back up to a sufficient power level
- The removal of the graphite-tipped control rods meant that the control channels were full of water
- The hottest part of the reactor at this point was the BOTTOM, which is NOT typical
- The reactor was on the cusp of the water boiling, which, with almost all of the rods pulled out of the unit, was an incredibly unstable state
- Pretty much all the safety systems were disabled at this point and once the reactor stumbled up, in the above state, to ~7% power, the operator, unwisely, decided to proceed with the test
- When the water started to boil and power levels began to rise, running the control rods back in, because they were so far out, and because of their graphite tips, they had the opposite effect and the reactor power surged 100-fold past the design limit
- This resulted in a massive pressure spike, rupturing the steam channels, which meant the graphite was suddenly exposed to oxygen
- The lack of containment meant that the resultant steam burst and chemical reactions blew the top off the unit, sending radioactive steam and graphite all over the place, starting numerous fires around the unit.
- The graphite, now no longer isolated from oxygen, began burning

They of course then tried to burry it from above and divers went into the pool below the unit to work control valves, a pool in which corium had already penetrated due to the meltdown. The power spike of course caused an LOC incident, but as you've noted, the LOC wasn't what initiated the incident, which is why I noted that what transpired at Chernobyl wasn't possible at other plants, which were LWR's (PWR and BWR) and HWR's. Both LWR incidents were LOC's.

 

[addyguy]

I was 10 when it happened, and I remember the concern it caused. My dad was a scientist, and he took a great deal of interest in it.

I'm really enjoying the series, and seeing all the mis-steps that made it such a huge disaster.

 

[LeakySeals]

It's that background music. It keeps me watching more than anything else anticipating what's about to happen.

 

[Andrew1972]

I like the series.

I am not a fan of this type of power, people constantly screw up since the dawn of time and are involved with design, maintenance , construction and operation of plants.

 

[Bottom_Feeder]

'The Cars of Chernobyl' from Jalopnik:

https://jalopnik.com/chernobyl-s-cars-paint-a-fascinating-and-grim-picture-o-1835134720

 

[Quattro Pete]

Just finished watching the first 4 episodes. It forced me to revisit this disaster. I realized I did not have all the details.

I lived about 400 miles away from Chernobyl at the time. I'm sure I got more than my fair share of direct and indirect radiation from consuming contaminated food.

We were administered iodine, but that was only 4-5 days after the incident, which would have been too late for it to be effective anyway, so it probably just caused more harm than good.

 

[Wolf359]

I guess one of the crazy things about it is that they were running a safety test and as part of the test, they disabled all the safety systems. Plus they weren't that familiar with all the design quirks of the reactor so when the parameters were too far out of whack, the thing blew up which no one thought it could actually do.

Must be one of those strange things the Russians do, I remember when I worked at a gas fired power plant, they had a room with racks and racks of backup batteries for the time when there's a power outage and there's no power. I believe the test they were running was trying to see if the turbine could be used to provide power for a minute or so during an outage as it took a minute for the diesel generators to fire up. Of course at the time I worked at that plant was in the 90's so it was after Chernobyl so not really sure if that was a standard thing or something they did afterwards.

 

[dailydriver]

Originally Posted by Quattro Pete
Just finished watching the first 4 episodes. It forced me to revisit this disaster. I realized I did not have all the details.

I lived about 400 miles away from Chernobyl at the time. I'm sure I got more than my fair share of direct and indirect radiation from consuming contaminated food.

We were administered iodine, but that was only 4-5 days after the incident, which would have been too late for it to be effective anyway, so it probably just caused more harm than good.



I HOPE that you get at least HALF yearly checkups currently!

If there ever was a 'predisposition' for problems, that is it.

 

[ctechbob]

The companion podcast to the series is worth a listen to as well. Its one podcast per episode and goes into a little further detail than what they show on TV.

 

[OVERKILL]

Originally Posted by Wolf359
I guess one of the crazy things about it is that they were running a safety test and as part of the test, they disabled all the safety systems. Plus they weren't that familiar with all the design quirks of the reactor so when the parameters were too far out of whack, the thing blew up which no one thought it could actually do.

Must be one of those strange things the Russians do, I remember when I worked at a gas fired power plant, they had a room with racks and racks of backup batteries for the time when there's a power outage and there's no power. I believe the test they were running was trying to see if the turbine could be used to provide power for a minute or so during an outage as it took a minute for the diesel generators to fire up. Of course at the time I worked at that plant was in the 90's so it was after Chernobyl so not really sure if that was a standard thing or something they did afterwards.


The "test", I wouldn't necessarily call it a "safety" test, was to determine whether the inertia of the turbine would produce sufficient electricity as it slowed to run the pumps for the period between disconnect of supply power and backup generator fire-up. Typically, that power would be provided by the grid, so the purpose of the test was to assume that this had also failed. It wasn't a necessary feature; the time between such an event and generator fire up was not long enough to cause issue, they were simply keen on seeing if they could reduce or eliminate that gap by capitalizing on the spinning mass of the assembly during slow-down.

They had already successfully tested this on another unit, so it certainly wasn't imperative that it be tested on this one, it was more of, as you noted, one those strange things the Russians do.

I also wouldn't say they weren't familiar with the design quirks. The RMBK was a well established reactor at this point; a reasonably mature design. The problem was that it was inherently less safe than BWR's or PWR's, which is why even the soviets were moving away from these units. The operator intentionally made decisions and performed tasks that made the unit unstable and unpredictable, including violating operation protocol by removing almost all the control rods and then despite the unit's fragile state, STILL decided to try and run the bloody test.

 

[OVERKILL]

Originally Posted by Quattro Pete
Just finished watching the first 4 episodes. It forced me to revisit this disaster. I realized I did not have all the details.

I lived about 400 miles away from Chernobyl at the time. I'm sure I got more than my fair share of direct and indirect radiation from consuming contaminated food.

We were administered iodine, but that was only 4-5 days after the incident, which would have been too late for it to be effective anyway, so it probably just caused more harm than good.



Wow! That would have been intense! Were you in the path of the smoke and contamination due to the winds or did that miss you?

 

[addyguy]

I know the fallout hit a very large area, but I think you would be safer than many 400 miles away...that is a long way away.

The area housed workers...not sure it was huge farming or food-distribution area, so your food was most likely okay.

I know that doesn't really help in a situation like this!

 

[Wolf359]

Originally Posted by OVERKILL
Originally Posted by Wolf359
I guess one of the crazy things about it is that they were running a safety test and as part of the test, they disabled all the safety systems. Plus they weren't that familiar with all the design quirks of the reactor so when the parameters were too far out of whack, the thing blew up which no one thought it could actually do.

Must be one of those strange things the Russians do, I remember when I worked at a gas fired power plant, they had a room with racks and racks of backup batteries for the time when there's a power outage and there's no power. I believe the test they were running was trying to see if the turbine could be used to provide power for a minute or so during an outage as it took a minute for the diesel generators to fire up. Of course at the time I worked at that plant was in the 90's so it was after Chernobyl so not really sure if that was a standard thing or something they did afterwards.


The "test", I wouldn't necessarily call it a "safety" test, was to determine whether the inertia of the turbine would produce sufficient electricity as it slowed to run the pumps for the period between disconnect of supply power and backup generator fire-up. Typically, that power would be provided by the grid, so the purpose of the test was to assume that this had also failed. It wasn't a necessary feature; the time between such an event and generator fire up was not long enough to cause issue, they were simply keen on seeing if they could reduce or eliminate that gap by capitalizing on the spinning mass of the assembly during slow-down.

They had already successfully tested this on another unit, so it certainly wasn't imperative that it be tested on this one, it was more of, as you noted, one those strange things the Russians do.

I also wouldn't say they weren't familiar with the design quirks. The RMBK was a well established reactor at this point; a reasonably mature design. The problem was that it was inherently less safe than BWR's or PWR's, which is why even the soviets were moving away from these units. The operator intentionally made decisions and performed tasks that made the unit unstable and unpredictable, including violating operation protocol by removing almost all the control rods and then despite the unit's fragile state, STILL decided to try and run the bloody test.


I think they will cover it in the final episode, but in the wiki, it mentions that the tips of the control rods were covered with graphite which instead of slowing down the reaction, actually increased it. So that's why the plant blew up when they hit AZ-5 instead of shutting it down. That was a design quirk that they weren't really familiar with because the Soviets kept so many things secret. It shouldn't really have mattered that much if it had been operating inside parameters, but it was too far outside the parameters they had originally envisioned.

And yes, it was a strange test. There were 3 other reactors near the site. I think it would have been very unlikely for all of them to be shut down and the place to have no power but I suppose anything is possible, maybe an issue with the connection to the grid would have prevented it from getting power from the other reactors. At least with the gas plant I was at, it was the only plant in the area and if it was off the grid and both generators were offline, it would need backup power to continue to run the pumps etc for an orderly shutdown.

What's somewhat crazy is that even though the whole area was evacuated, they kept running the other 3 reactors for years afterwards, I think they finally shut down the last reactor there in the 2000's.

 

[Quattro Pete]

Originally Posted by Wolf359
I think they will cover it in the final episode, but in the wiki, it mentions that the tips of the control rods were covered with graphite which instead of slowing down the reaction, actually increased it. So that's why the plant blew up when they hit AZ-5 instead of shutting it down.

They already covered it in episode 4.

 

[Wolf359]

Originally Posted by Quattro Pete
Originally Posted by Wolf359
I think they will cover it in the final episode, but in the wiki, it mentions that the tips of the control rods were covered with graphite which instead of slowing down the reaction, actually increased it. So that's why the plant blew up when they hit AZ-5 instead of shutting it down.

They already covered it in episode 4.

Right, but the operators didn't know that at the time and that wasn't really covered in episode 4. Episode 5 looks like the trial so maybe more of it will come out.

 

[Quattro Pete]

Originally Posted by OVERKILL
Wow! That would have been intense!
It really wasn't intense because we didn't learn about it until a few days after the explosion. By that time, the cloud already passed over us. Living in a communist country at that time meant lack of facilities to properly and proactively measure radioactivity as well as overall unwillingness of the government to share such information (even if it were available) in order to keep people in the dark and avoid wide spread panic and revolt. Still, even if information about an approaching radioactive cloud was disseminated quickly, I'm not sure it would have changed much. It's not like people could have just gotten up and left (where would they go?) on such a short notice or could have stopped eating. Food supply in those days wasn't all that great to begin with. Farmers had to go ahead and plant their crops as usual, or else, come Fall, the country would have starved.

Still, being 400 miles away meant a lot smaller dose of radiation relative to some other areas.

Quote
Were you in the path of the smoke and contamination due to the winds or did that miss you?

Not only did the radioactive cloud fly over us, it also rained during those days, which means the rain pushed it down and contaminated the soil and farm lands for many years to come. See maps on slides 5, 6, and 11 in this slide deck. (Warsaw area)

 

[Andrew1972]

My Russian neighbors father in law lives permanently with them (green card). He is a World War II vet and retired nuclear physicist who worked on USSR programs both weapon and energy.

I wish I could speak directly(only speaks Russian) to ask his view of what happened.