News Chernobyl disaster: Ukraine marks 30th anniversary

[Notebook]

Commemorations are under way in Ukraine to mark the 30th anniversary of the nuclear disaster at Chernobyl.

Sirens were sounded at the same moment as the first explosion at the reactor, in the early hours of 26 April 1986.


http://www.bbc.co.uk/news/world-europe-36136286

Remember it well, didn't seem serious at the time, then it did,

N.

 

[Thunder Chicken]

I actually just taught a class discussing the Chernobyl accident a few days ago as part of an engineering course. The students in that course weren't born yet when that happened, and many of them don't know anything about it. They are awestruck and horrified by the stories of the operators and firefighters, the evacuation of Pripyat, the reactor damage itself, and the efforts of the liquidators during the cleanup.

I'm a bit torn about presenting all of this in detail - part of me wants them to understand that nuclear power, particularly in Generation III+ plants, can be utilized very safely. But on the other hand, the safety of the present fleet and of the newer designs was inspired on the hard lessons on what could go wrong. The technical engineering lessons are valuable, and so is the understanding of the human factors that can lead to accidents even when the technology works as designed.

 

[Andy44]

Well, when I saw footage of those guys on the roof shoveling stuff into the burning reactor core with coal shovels I knew they were having a really bad day. I don't think I'm wrong in thinking that looking directly at a burning, unshielded fission reactor with just a shower cap on is probably a sign that something has really gone wrong.

But yeah, the magnitude and reach of the contamination later came as a shock.

 

[ADSWNJ]

Radiation spread map


Those guys with the shovels, or flying helos to drop sand in the gaping hole ... just wow! Ditto those who mined underneath the reactor to stabilize the foundation.

I found this silent documentary, which I think gives the right somber tone to this anniversary:

https://www.youtube.com/watch?v=nbCcutzXzYg

 

[Andy44]

Wow. That video gives me chills.

 

[Thunder Chicken]

Well, when I saw footage of those guys on the roof shoveling stuff into the burning reactor core with coal shovels I knew they were having a really bad day. I don't think I'm wrong in thinking that looking directly at a burning, unshielded fission reactor with just a shower cap on is probably a sign that something has really gone wrong.

This photo gives me the shivers:

The alternating light and dark areas along the bottom are the shadows of the film advance mechanism blocking radiation exposure. These "biorobots" were shoveling bits of fuel bundles and graphite and other debris back into the reactor containment. 40 seconds, run out, shovel a few things in, drop shovel and run.

 

[Andy44]

40 seconds is 40 seconds too long. Good lord that photo is chilling.

Why are they called "biorobots"? Is that a reference to them being expendable or something? Those guys all paid a steep price for what they did in those days.

 

[Urwumpe]

There is also the story of a German company, which supplied especially adapted concrete pumps to the USSR for encasing the reactor wreck afterwards.

http://www.pmw.de/cps/rde/xchg/SID-576D4F73-7A63A04B/pm_online/hs.xsl/9394_DEU_HTML.htm

http://www.pmw.de/pm_online/data/BP_1133_US.pdf



---------- Post added at 10:21 AM ---------- Previous post was at 10:16 AM ----------

Why are they called "biorobots"? Is that a reference to them being expendable or something? Those guys all paid a steep price for what they did in those days.

Because the attempts with robots failed. AFAIR, the only robot that survived longer than a few seconds there arrived late and was by Lavochkin, the design bureau that usually designed interplanetary probes and which created the Lunochod rover.

http://chernobyl.blog.hu/2014/03/17/csernobil_robotjai

---------- Post added at 10:34 AM ---------- Previous post was at 10:21 AM ----------

Well, when I saw footage of those guys on the roof shoveling stuff into the burning reactor core with coal shovels I knew they were having a really bad day. I don't think I'm wrong in thinking that looking directly at a burning, unshielded fission reactor with just a shower cap on is probably a sign that something has really gone wrong.

A few decades earlier, exactly that saved the day... during the Windscale pile accident in the UK. The reactor manager climbed on top of the reactor building and watched how things turned out, especially noticing that most ways to stop the graphite fire failed, just like they later failed for Chernobyl.

---------- Post added at 10:58 AM ---------- Previous post was at 10:34 AM ----------

And there are still many reactors of the same type as Chernobyl around and running, for example Leningrad I, the first block of it is going to be decommissioned this year:

What I find interesting among the photos of it:

This system is used for exchanging fuel bundles during operation, 400 times every year.

I just read a scientific paper about this device and a simulation model that was created for analyzing it.

 

[Ravenous]

I'm a bit torn about presenting all of this in detail -

The more detail you give them, the better - there are some real lessons here. At the time I was an engineering student and read an analysis of what went wrong in one of the "trade" magazines (this all came out openly after the event). There were very specific aspects of the reactor design which made it unstable when run at low power, strangely. Xenon gas build up etc.

The final irony is that when the core started misbehaving, they tried to lower rods to absorb neutrons. These displaced water and this had the effect of increasing the power for a while as they started to descend. That was enough to buckle some of the rods part way in and after that point there was no hope of controlling it.

They simply didn't know enough, or at least think enough, about the machine at the time.

 

[Urwumpe]

The final irony is that when the core started misbehaving, they tried to lower rods to absorb neutrons. These displaced water and this had the effect of increasing the power for a while as they started to descend. That was enough to buckle some of the rods part way in and after that point there was no hope of controlling it.

They simply didn't know enough, or at least think enough, about the machine at the time.

More funny is: The rods had been designed! that way to provide a noticable increase in neutrino flux so that the movement of the rods can be monitored. That was why 4.5 meters of the control rods had been graphite.

No problem in normal operation. But in Chernobyl, this design decision was fatal, because in a situation, where the neutron flux was already increasing at the top of the reactor, this decision also increased it at the bottom of the reactor as well.

Also in Chernobyl, the operators removed control rods that should NEVER be removed in normal operation for getting the power at least back to the power level of 200 MW in time - 500 MW less than required for the test. And had to disable all automatic shutdown systems for doing that.

 

[RisingFury]

And there are still many reactors of the same type as Chernobyl around and running, for example Leningrad I, the first block of it is going to be decommissioned this year:

In Soviet Russia, nuclear reactors decommission you

 

[Urwumpe]

In more political news: Today it was announced that the German nuclear reactor operators could pay 23.4 billion € for moving all responsibility for their nuclear waste to the German government. The responsibility for deconstructing the nuclear reactors and transporting their waste to the storage would stay at the operating companies, the costs for that are estimated to be at 19.6 billion €. That is all the result of negotiations of the nuclear energy commission. It is expected that the German government will follow the recommendation.

The 23.4 billion € is less then recommended by ecologists, who suggested a risk multiplier of 50% - this is now down to 35% for additional costs.

This is it: 30 years after Chernobyl, the German use of nuclear fission reactors is finally declared over and the process also solved on the financial side.

Now lets hope that nuclear fusion is also getting ready in time when we begin to need it.

 

[Thunder Chicken]

Why are they called "biorobots"? Is that a reference to them being expendable or something? Those guys all paid a steep price for what they did in those days.

It was a dark euphemism. Real robots were attempted for the cleanup, but the electronics fried rapidly in the radiation environment.

 

[Lucy]

It was a dark euphemism. Real robots were attempted for the cleanup, but the electronics fried rapidly in the radiation environment.

Yeah, I read some good articles on the Chernobyl Robots today in connection with this.

http://www.the-scientist.com/?artic...hat-Robots-Couldn-t-Handle-Chernobyl-Cleanup/

That article, from all the way back in 1990 (So just a few years ago, right?) points out the issues they faced; all the robots they used were designed for other purposes and either couldn't cope with the high radiation, or the ones which could got fried when they sprayed water on them trying to decontaminate them (sounds like a winning strategy).

The US had some active, much more advanced and better suited robots at the time cleaning up Three Mile Island, but the relations between the USSR and the USA at the time meant that nobody in power wanted to ask the USA for help; and, potentially, that the USA might not want to effectively donate cutting-edge robotics technology to a country which was, at the time, a potential nuclear threat. The robots that did get used probably saved something like 500 lives, and they're all on display in a museum somewhere in the Exclusion Zone; and, as with everything else there, extremely radioactive.

 

[ADSWNJ]

Who here lived closest to Chernobyl at the time of this disaster?

I was talking to a colleague at work today who lived in Kiev (100km away) for years through and after the disaster. Chilling stories about his dad being one of the clean-up crew (and surviving by drinking copious amounts of alcohol on every clean up shift, weirdly?!)

 

[Loru]

~650km. We recieved Lugol's iodine in kindergarten to prevent absorbtion of I 131 and prevent thyroid cancer. I was 4 at the time.

 

[Andy44]

In Soviet Russia, nuclear reactors decommission you

Not really funny, sorry.

 

[Urwumpe]

1434 km. :hail: I was 7 at that time, we only ate less mushrooms collected from the forests here.

 

[Fabri91]

1667.65 km from here.

 

[jedidia]

I read an article a few days ago that linked the high cancer rates in the region to contaminated food grown from the soil.

It was a news article, not a scientific one, so it was pretty much devoid of any useful data explaining the connection. It struck me as a bit odd why it singled out the food... If the soil was still this contaminated, wouldn't that by itself already constitute for a major increase? Or is there groundwater contamination that is not directly dangerous on the surface?
I'm not saying they are wrong, I just don't get where they made the link to the food as major contributor...