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Chernobyl Nuclear Disaster

Posted April 25, 2012 10:00 AM by cheme_wordsmithy

Tomorrow is the 26th anniversary of one of the most infamous nuclear accidents ever to occur - Chernobyl. It was the only commercial nuclear power plant accident ever directly linked to radiation-related fatalities, and is considered the worst nuclear disaster in history. Although not a cheerful memory, to be sure, it is certainly one that shouldn't be forgotten as we continue to use and develop nuclear power.

(Credit: Yahoo News) -->

The Incident

The Chernobyl nuclear power plant was located in northern Ukraine near the city of Chernobyl. On April 25, 1986, reactor 4 of the four-reactor plant was scheduled to be shut down for maintenance. Operators started a test on reactor 4 during this time, resulting in an explosion of the reactor a day later (April 26). During the subsequent fire, which burned for 10 days, an estimated 7 to 8 tons of radioactive material was released into the atmosphere, including plutonium, graphite, iodine-131, and cesium-137. Winds blew much of this material into the neighboring country of Belarus and the surrounding regions.

The Cause

The nuclear operators and lead engineer were largely at fault for what happened at Chernobyl. The engineer decided to run an experiment to test how long the reactor could be cooled using only residual steam and coasting turbines to run the coolant pumps. To run these experiments, they had to bypass several safety systems, which was in violation of their own protocols. To make matters worse, the grid controller requested the reactor continue to supply power past the scheduled shut down time, delaying the test and keeping the reactor running at low power for nearly twelve hours. This low power operation eventually caused a severe power drop, which (after a few bad decisions) resulted in a chain of events leading to an uncontrolled power surge and explosion.

But the faulty design of the reactor is as much to blame for the accident as its operators. The Chernobyl nuclear plant housed a graphite-moderated nuclear power reactor design called RBMK (Reaktor Bolshoy Moshchnosti Kanalniy, or "High Power Channel-type Reactor"). This design had multiple flaws, not the least of which was its instability at low temperatures. During the testing, this led operators to turn off cooling pumps in an effort to raise the power back to higher levels. But the reactor had a large positive void coefficient, which meant that in the absence of coolant, power would increase (rather than decrease) as temperatures rose. The power increased so rapidly that one operator quickly called for emergency shutdown by hitting the BRB (big red button).

(Don't push the big red button... Credit: RPGSobs)

But the graphite tipped control rods (another design flaw) which were pushed back into the reactor actually further increased the reaction. This led to an out-of-control cycle known as a feedback loop, which ended in a massive power spike and the resulting steam explosion which blew apart the reactor head.

Effects

One person died instantly as a result of the explosion, while a second died shortly after due to injuries. The release of radiation directly caused the deaths of 28 people due to acute radiation syndrome (ARS), and a total of 134 cases were reported. The most significant effect for the offsite population was the large proportion of childhood thyroid cancers diagnosed since the accident, likely due to the intake of radioactive iodine fallout. The radiation also killed plant life within a 10 km2 area surrounding the site, giving it the name 'Red Forest' from the color of the dead pine trees. The area (originally called Wormwood Forest) has since recovered and even flourished due to the lack of human activity in the area. Most of the radioactive material is concentrated in the soil.

(Aerial photo of the Chernobyl power plant after the accident. - Credit: AP Photo/Volodymir Repik) -->

A number of studies have been done on the health problems caused by Chernobyl, although a lot of the information and conclusions are clouded in uncertainty and laced with assumptions which could drastically affect the numbers. Suffice to say that radiation is not a good thing.

Cleanup of the site has cost many millions of dollars and is still continuing over 25 years later. Some engineers say the new containment structure being erected will not be completed until near 2020.

Lessons Learned

The worst nuclear disaster in history is not likely to be forgotten any time soon, especially by the voices that speak against nuclear power. It is an important reminder of the reasons why there are established protocols and safety systems, and why operator and engineering experience is so important.

But beyond these fundamental lessons, Chernobyl has little relevance to the nuclear industry. Realistically, the disaster was an unfortunate consequence of a uniquely flawed design much different from American reactors at that time and most modern reactor designs today. For instance, all reactors now implement a self-regulating negative temperature coefficient design, which would have prevented the extreme drops and spikes in power and temperature. In addition, the reinforced concrete and steel containment structures presently built for most reactors would have contained the release of radioactive material into the atmosphere.

If anything, the Chernobyl disaster keeps me honest in my perspective on nuclear power. Regardless of the inherent safety of nuclear reactors today, the fact remains that there is enormous power behind these feats of engineering and science - power that can have dire consequences if handled foolishly.

References

Gerd Ludwig Photography - Chernobyl Cleanup: No End In Sight

Nuclear Fissionary - What Happened at Chernobyl

World Nuclear Association - Chernobyl Accident 1986

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#1

Re: Chernobyl Nuclear Disaster

04/25/2012 10:46 AM

"Realistically, the disaster was an unfortunate consequence of a uniquely flawed design much different from American reactors at that time and most modern reactor designs today." See previous comment within the article, "The nuclear operators and lead engineer were largely at fault for what happened at Chernobyl. The engineer decided to run an experiment..." The lesson here may be: There is no such thing as a machine that will never fail, and you cannot make anything idiot-proof... it is difficult to design something that is idiot-resistant.

"But beyond these fundamental lessons, Chernobyl has little relevance to the nuclear industry." It is difficult for me to form a well worded comment about this... something along the lines of 'the world becoming a victim of the consequences of whimsy' or 'the tremendous responsibility to mankind, not simply making power'... If there are other members with similar thoughts, let's discuss them.

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#7
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Re: Chernobyl Nuclear Disaster

04/26/2012 11:22 AM

They attribute the Chernobyl accident to the operators not being properly trained for the job.

The aftermath of the accident could have been greatly reduced if the USSR didn't try to cover it up trying to handle it themselves. They didn't even disclose there was an accident until Sweden started reporting increased radiation levels in the atmosphere.

Practically all of Europe sustained some contamination that could have been averted if it wasn't for the Soviet Government.

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#2

Re: Chernobyl Nuclear Disaster

04/25/2012 10:59 AM

Listening to events unfold, as relayed by various news broadcasting agencies at the time, was a deeply troubling and moving experience.

There was a set of photographs of the town of Pripyat presented as part of a display outside London's Natural History Museum a couple of years ago. The images were just as troubling.

This sort of thing must never recur.

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#3

Re: Chernobyl Nuclear Disaster

04/25/2012 2:14 PM

I was going to email you about this (I saw it when looking for topics for the "On This Day" blog) but I forgot about it. Glad that you didn't!

There's going to be a show about radioactive wolves on PBS next Monday. It will be interesting to see the effects on the animal species that are still living there.

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#4
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Re: Chernobyl Nuclear Disaster

04/25/2012 2:31 PM

The radioactive wolves report is part of the PBS series Nature. Different PBS stations will be broadcasting this program at different times. Here in the New York City area, WNET will be broadcasting this show tonight, Wednesday April 25 at 8:00 PM. Check your local listings.

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#6
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Re: Chernobyl Nuclear Disaster

04/26/2012 10:36 AM

Saw it last night. Recommend to all. A lush Nature Preserve is taking over in the shadow of the reactor ruins. They are actually reintroducing species that had disappeared due to human habitation, swamp draining and land clearing. The starkness of the ruins of farms, high rises and the reactor buildings increases the dramatic nature of the Preserve. The animals actually use some of the ruins to get in out of the weather. Wolves perched on rooftops to scan the horizon for prey. One of the best programs you could watch.

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#5

Re: Chernobyl Nuclear Disaster

04/26/2012 1:48 AM

"A number of studies have been done on the health problems caused by Chernobyl ..."

True, apart from the initial industrial accident (28) and the later small number of thyroid cancers (easily prevented and easily treatable) the health effects have been very hard to find.

There is poorer health in the region but it's consistent withe the poor health found in similar poor rural areas. Overall it's less than the effects of smoking.

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#8
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Re: Chernobyl Nuclear Disaster

04/26/2012 12:20 PM

Here is an interesting link to that subject:

http://www.iaea.org/newscenter/features/chernobyl-15/liquidators.shtml

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#9
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Re: Chernobyl Nuclear Disaster

04/26/2012 7:18 PM

That's strange. A 2006 Greenpeace report says:

"... 93,000 fatal cancer cases caused by Chernobyl. .... 60,000 people have additionally died in Russia because of the Chernobyl accident, and estimates of the total death toll for the Ukraine and Belarus could reach another 140,000."

Guess which one was widely reported?

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#19
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Re: Chernobyl Nuclear Disaster

05/01/2012 10:24 AM

I don't know about that. The Government pays people to live in the contaminated areas. There was an issue that came up about stopping that. Periodically they have to take out the top soil of the farmlands and bring in new top soil. So the affects are still there, that sounds a little more severe than smoking. They still have people coming into the clinics with radiation poisoning. Where do they take that contaminated soil?

One positive affect of the disaster is that it brought countries closer together in regards to nuclear power. It was one of the first Joint U.S.-USSR efforts that was successful and now there are over 35 other countries that have climbed onboard in the standardizing safety in nuclear powerplants.

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#20
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Re: Chernobyl Nuclear Disaster

05/02/2012 7:32 PM

I remember when I was just a young lad in grade-school... Our science teacher was telling us how if the tiniest particle of radioactive material got inside our bodies that it would cause mutations and tumors. Scared the hell out me! I think he died from lung cancer btw. But later I learned just how much radioactivity there is floating around in our environment, and I figured he must have been wrong. Then again, maybe there are different types of radioactivity.

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#21
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Re: Chernobyl Nuclear Disaster

05/03/2012 3:52 PM

Are you maybe confusing radioactivity with radiation?

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#10

Re: Chernobyl Nuclear Disaster

04/27/2012 1:20 AM

I thought I'd throw something in here. I had a couple of graphs sitting around that i might make a comment on. Not sure where I got them from right now though.

It seemed to me that there was a correlation between this industry and the climate warming- which to me makes sense when you consider how hot this stuff gets.

I realize that there are a lot of factors that go into the warming of our planet, but I just wonder what impact the production of these kind of materials has. And I'll never forget how the sky looked the fall and winter following this event. It was a deep red, almost purple. In fact I remember the song "Red Sky" by the group The Fixx being played around then. At that time there was a lot of talk about acid rain (something that along with the red skies I would attribute more to burning gasoline). But, if I remember right, it was around this time that scientists started making a big deal about a hole in the ozone as well. Just though I'd throw this in here.

And I might add that follwing the disaster in Japan, we ended up with a very warm, almost snowless winter here (in Pittsburgh) where I live.

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#11
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Re: Chernobyl Nuclear Disaster

04/27/2012 8:44 AM

Watch out for the pitfall of correlation vs causation.

To illustrate the point my statistics professor had similar data showing a very strong positive correlation between the amount of bananas imported into the US and the number of pregnancies. Hopefully it is obvious that we can't cause more pregnant women simply by importing more bananas.

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#12
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Re: Chernobyl Nuclear Disaster

04/27/2012 9:24 AM

Ah yes, but what did they do with that ba..... on second thought, I'm certain that off color mental trap is exactly what your statistics professor had in mind so the class will remember that something that correlates does not always indicate a causation. I may pilfer that example one day.

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#14
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Re: Chernobyl Nuclear Disaster

04/27/2012 5:43 PM

That might not have been such a ridiculous comparison after all when you consider that some cultures think of the banana as an aphrodisiac. And the correlation may have still been right when you consider the nutritional value of the banana and the cravings of all those partners.

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#15
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Re: Chernobyl Nuclear Disaster

04/29/2012 1:02 AM

After the important point made by ChaoticIntellect, cautioning against confusing correlation with causation, I would contend that the two graphs provided do not actually show a strong correlation between nuclear power generation and global warming.

.

The period from 1900 to 1945 looks remarkably similar to 1945 to 1990. Since total nuclear power production had leveled off by around 1987 and had been at at least 1/2 that value 10 years prior, all other things being equal, I would expect 1970 to 1990 to be significantly steeper than 1925 to 1945 if nuclear power were causing a significant increase in temperature.

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#16
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Re: Chernobyl Nuclear Disaster

04/29/2012 5:42 AM

Yeah, like I said I was just throwing it out there to look at. I had the graphs sitting in my doc's folder for a while. But it would be nice to see a temperature graph that went a little further back though. If anything I would imagine the two spikes may be related to CO2 emmissions more than anything.

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Re: Chernobyl Nuclear Disaster

04/29/2012 2:33 PM

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#18
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Re: Chernobyl Nuclear Disaster

05/01/2012 2:44 AM

Thanks for the graphs! Got a chance to look back a little further now.

Although I'm not to comfortable with the data on these graphs. I mean I know that we have been able to take a look back at the CO2 record through ice core samples. But I don't know how they determine the temperature swings. And it seems to me that graph 1's temperature swing don't quiet coincide with graph 2's temperature swings.

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#13

Re: Chernobyl Nuclear Disaster

04/27/2012 10:32 AM

Saw that documentary show "Nature" on PBS last night. Very interesting. What surprised me was the reintroduction of Bison in the hot zone. Heck, I didn't even know that the Ruskies even had them! LOL

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#22

Re: Chernobyl Nuclear Disaster

05/15/2012 8:39 AM

I remember this very well. On the day of the disaster I was camping on the high Antrim Pleatue in County Antrim Northern Ireland. I heard about it on my sw radio, not thinking that it would in anyway endanger me, I tucked myself up in my sleeping bag and went to sleep. The next morning it was pissing down. I collected some water from one of the bog pools and made a cup of tea. Settling down I put the radio on, and it began to squeal like a banshee!!! For two days my radio refused to work until I returned home. All of the sheep in that area were destroyed because of Radioactive contamination. That was 26 tears ago and sheep are still forbidden to graze there! Lately I developed sever thyroid and pituitary gland problems. The UK took great trouble to monitor the sheep but did not test a single human during or after the event! Thyroid and Leukemia type cancers have risen dramatically in the area. The Government refuse to investigate.

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