Chernobyl

[Pilar]

The concrete sarcophagus that serves as a makeshift containment for the contaminated reactor number 4 at Chernobyl is failing structurally. A great quantity of highly radioactive dust and debris is contained inside the structure.

That's the snatch of news I heard on the radio anyway. I'll try to find out more.

Chernobyl was a Russian designed, RBMK type, graphite moderated nuclear power generating station located in the Ukraine. There was an accident with the reactor some 17 years ago that caused an explosion, a fire in the graphite elements and eventually a complete meltdown of the remaining fuel materials in the core.

The parts of the plant that scattered during the accident were picked up by 'biological robots'. These were Red Army volunteers who traded their lives for an early retirement from military service, lifetime medical care and pension. They would train for weeks to clear a certain section of the building roof or surrounding areas of radioactive debris. The typical exposure time was only 10 minutes. Many have since died.


This facility was encased in a huge makeshift concrete structure the Russians call 'The Sarcophagus'. Now 17 years later the building is failing.

I'll get more and post it.........

[ 04-23-2003, 09:57 AM: Message edited by: Pilar ]

[The Fishing Geek]

Well if YOU aren't just the bluebird of freaking happiness!

That Chernobyl issue has been in the back of my mind for a couple years now. The dome has been crumbling for awhile, and it's gonna be bad when it comes down. VERY bad.

[Gus Orviston]

read about the same thing 5-10 years ago... They had guessimates and all on how much of the radioactive dust would get out, I don't remember the impact but it was VERY scary. I recall the aftermath being worse than the original meltdown by quite a bit.

Oh, and I remember of one of there solutions was to build a shell around it, but there are way too many issues to tackle it that way.

hopefully with more modern technologies and synthetic materials something could be built to mitigate some of the fall out?
gus

[ 04-23-2003, 09:52 AM: Message edited by: Gus Orviston ]

[Pilar]

Sorry geek, but I feel like I have to provide some balance .........

Collapse
http://www.agriterra.org/~wise/368/3610.html

Background
http://gis.esri.com/library/userconf...0658/p0658.htm

More Background
http://www.nea.fr/html/rp/chernobyl/c07.html

I think the amount of concern you have is directly proportional to what you know about radiological issues. This is scary stuff, I could not just sit on it.

[lost_sailor]

more cement!

a lot more

[GutZ]

We have plenty of Sand now. Why don't we use some of that?

[Hoosier Daddy]

DOH!!! :shocked:

[1pump]

On PBS years ago I saw an excellent documentary on Chernobyl. They had footage of the soldiers that Pilar described clearing the roof and dumping sand into the old reactor building while wearing lead-lined suits. What fun.
What really amazed me was the video someone shot from a helicopter. The reactor building had collapsed, and you could actually see the reactor core glowing red-hot, competely exposed! :shocked: :shocked: That's not something you see every day. Whoever shot that video is long dead, I'm sure.

[Pilar]

1pump, if you watch that video again, pay attention to the very poor quality and 'snowy' picture of the helicopter footage. The gamma flux is so high when they fly over the glowing pit that the radiation is ionizing the video tape and the electronics in the camera. You get a lifetime maximum exposure in seconds at those levels.

Does anyone know the name of that NOVA episode or approximate time it was shown?

[DanS]

I watched that same show. The guys that filmed those scenes were dead in a mtter of weeks. Did you see the pic of the radioactive glass blob that formed when the fuel rods melted the sand below them? Those pics were taken by a robot-mounted camera and you should have heard the Geiger counter on the thing go wild when it was shooting videos of the "blob".

Pretty freaky stuff..................

[GutZ]

Pilar;
I read through the links you posted and couldn't really pickup what they are planning to do.

Are they planning to build another "Sarchoghogus" or is there some other way to isolate the radioactivity? Just incasing it in concrete won't work will it? It will erode the concrete, right? Could they build a dam around the whole place and fill it with concrete or some other material? Something like a billion cubic yards but who cares?

I remember some thing from Carl Sagan, billions and billons of years ago , in which they were discussing how to indicate to future inhabitants of Earth where these horribly dangerously polluted sites may be. Over time recognizable landmarks will change. How do you let those future inhabitants know where these places are?

[1pump]

Does anyone know the name of that NOVA episode or approximate time it was shown?

<font size="2" face="verdana,arial,helvetica">I wish I knew. I would like to get a copy of it. I found one called "Return to Chernobyl" but that wasn't it.
I think I saw it on PBS at least 10 or more years ago. But I'll never forget that reactor core. I almost jumped up and ran screaming from the house just seeing it on TV. Gave me a serious case of the heebie-jeebies.
Gotta love those Soviets. They didn't say a word about it until the fallout was detected in Sweden. How far is that- about 1000 miles or more? [img]graemlins/eek13.gif[/img] The Swedes' suspicions were confirmed when the Russians asked for advice on extinguishing a graphite fire. Oops.

update- I think I found the NOVA documentary:

Suicide Mission to Chernobyl
originally broadcast 10/22/91

[ 04-25-2003, 12:16 AM: Message edited by: 1pump ]

[Pilar]

The 'plan' if there is one is to reinforce the existing building. Also there is some talk of constructing a cover over the site and the sarcophagus. The scale and cost of this proposed construction project are staggering.

What you have to understand is that the area around reactor 4 is a little like the surface of an airless planet. Completely inhospitable to humans. The reason the problem is so hard to solve is because the radiation levels and risk of contamination to anyone in that area is very high. Imagine a construction site operating under those conditions. Much of the work would be done using heavily shielded cranes.

Among the many concerns are

1) Building collapse and the Radioactive dust cloud that would produce. By estimates this would be worse and contaminate more Sq. miles than the original event.

2) Rainwater collecting in pools near masses of fuel lava that pooled in the basement of the building. Water is a 'moderator' for the fission reaction. It slows neutrons that are released by random fission from near light speed to slower 'thermal' speeds that are most likely to cause more fissions. If the number of thermal neutrons stays the same or increases the nuclear reaction is self sustaining or 'critical'. A large pool of water near or on a fuel lava blob may cause it to go critical and begin an uncontrolled nuclear fission reaction. It is unlikely but such a lava blob may even go supercritical and blow. The sarcophagus leaks through many cracks during every rain event and the water runs down into the ruined building and the levels underground.

3) Groudwater contamination. A makeshift concrete floor was tunnelled and pumped under the site. But it is incomplete and is allowing runoff to hit the groundwater. Strontium 90 contamination of test samples taken near the site confirm this contaminated runoff.

How do we order a copy of the 'Nova' episode?

[The Fishing Geek]

Lots of mentions of the video on Google, but I'm not finding it available to purchase.

[DanS]

Call WGBH in Boston at 1-888-255-9231. If it's available, they can help you.

[Pilar]

Melt down and go 'To China'? No, in most scenarios probably not. But this is very much what happened at Chernobyl. The nuclear fuel is spread out over a very large volume in this type of reactor. So it has a low density. As the fire burned the graphite away the fuel became more concentrated, increased it's reaction rate and reached temperatures hot enough to liquify concrete, rock, the mineral serpentine, steel, sand and the other materials in the reactor compartment. This lava then burned it's way down through the walls and floors until it hit the lowest levels of the building. It collected and cooled there in huge lumps. Most of the fuel from the core is unnaccounted for IE: 130 tons of the original 180 tons of fuel loaded in the core at the time of the accident.

The low fuel density is an alleged safety feature of the RBMK style reactors. The fact that this reactor has absolutely no primary or secondary containment in the design or that it has a positive coefficient of reactivity is ignored.

Translation. Containment is a strategy to 'contain' the byproducts of an accident like this one. In the pressurized water reactors (PWR) used in the US and throughout the civilized world there is a heavy steel pressure vessel surrounding the fuel. In theory the core could melt and would chill inside the vessel, preventing the lava flow or china syndrome we saw at Chernobyl. Also a feature of PWR plants is a heavy concrete and steel buiding surrounding the reactor. A second level of containment often built to withstand airplanes crashed into it, earthquakes, volcanic activity and floods. Chernobyl lacks any containment at all.

Positive coefficient of reactivity - the tendency of a nuclear reactor to increase it's reaction rate as the core gets hotter. The most likely scenario is a loss of cooling water, a very common occurance in a nuclear reactor. In an RBMK like Chernobyl #4 the water used to cool the core tends to limit the nuclear reaction rate. The graphite core remains when the water boils off and is the moderator. This is bad for obvious reasons. Most accidents are caused by a loss of cooling for the reactor core. Any time the power generator shuts down the reactor loses it's heat sink and heats up quickly.

PWR systems use water as a moderator. When the system heats up the water boils and the core shuts down because the moderator is gone. This is known as a negative coefficient of reactivity. The hotter it gets, the more it shuts down.

Hope that helps, sorry for the technical rant but it may help you understand the issues, 1pump.

[GutshotApe]

Pilar - Didn't you once post on here somewhere that you were a submariner on a nuke sub?

I, too, was a crewman on a nuke, but it was a surface ship...a cruiser. I wasn't a "nuke" and didn't learn much about nuclear reactors...they told us dumb radarmen to leave all that up to the nukes...and don't worry about it. My bunk was in the compartment immediately adjacent to one of our 2 reactors...but they didn't even give us film badges to check our exposure.

"Trust us" the nukes said....we did...and I'm still here, relatively normal...so far....

[Pilar]

Gutshotape, yes, long and black and never comes back. EM1/SS, I stood watch in the engine room underway as the electric power plant operator and sometimes the throttleman. In port I got to babysit what we called 3 meter island as shutdown watch while it was shut down. All in all I spent many, many hours just a few feet away from the aft reactor compartment bulkhead. It gave me alot of time to study and think about nuclear power and the issues involved.

In NPTU, we studied the TMI accident ad Nauseum. Navy nuclear power is a little safer than the civilian side because of the military attention to detail and the intensity of the crew training. The civilian side is a bit more laid back. Add to that the whole operated for profit aspect of civilian nukes and the potential for cutting corners and accidents is there.

Most of the guys running the civilian nukes here in the US have the same background I have. Ex navy nukes are the preffered applicants for power plant operators.

[1pump]

Oh, OK. So water is a moderator. That answers another question I had about the two subs the US Navy has lost, the Scorpion(SSN-589) and the Thresher(SSN-593). The Russians have lost more than a couple as well. You'd think that reactors lying around on the seabed would make people a little uptight.

[Miss B Haven]

Pilar- I was wondering? I was kinda thinking all that nukeknowledge came from losing the yellow po! Now that I know where all that power knowledge came from... I'm gunna have to killya! :grin:

Peace!- Mel

[1pump]

Hey Pilar, tell me something. Won't a runaway reactor core actually burn it's way in to the ground until it hits groundwater (aka the "China Syndrome") and causes a huge steam explosion?
I think I heard about this somewhere. :whazzup:

[sinker]

The Russians have lost more than a couple as well

<font size="2" face="verdana,arial,helvetica">The Russians in the past have used some scary methods for disposing of mothballed ships. Instead of dismantling them and doing something "decent" with the nuke stuff, they just sink them. I once heard how many they had sunk and it's down right scary.

Not sure decent is the right word but I know good isn't the right word either.

I hate this nuclear crap. Scares me to death.