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View Full Version : What really happened at Chernobyl



Glom
2006-May-13, 03:51 PM
Here it is. (http://www.freedomforfission.org.uk/acc/chernobyl.html#chain)

Apparently the fourth years had to do a lot about it for their version of the exam I failed a couple of days ago (damn fusion!). But I managed to grab a lot of information from their resources. It is clear now where they went wrong. I mean we knew that uranium-graphite-water sucked since before Calder Hall.

swansont
2006-May-13, 09:04 PM
The discussion of the Xe-135 is a little misleading. The site implies that Xe-135 only converts t Xe-136 at high power ("At full power, the absorption of neutrons converts it to xenon-136, but at this lower level, xenon-135 builds up poisoning the reaction."). Xe-135 builds up after any reduction in power (assuming we've started in steady-state), because it's produced faster than it's removed, until you reach a new steady-state. But it's always capturing neutrons.

Also, "Now add the xenon-135 to the mix, which accumulates to high levels at low power levels without the large number of neutrons flying around to destroy it." ignores that Xe-135 is radioactive and will decay on its own.

Glom
2006-May-13, 09:43 PM
Ah yes. I've made some edits.

farmerjumperdon
2006-May-15, 12:29 PM
Very interesting page. Thanx.

Glom
2006-May-15, 01:15 PM
Very interesting page. Thanx.

Thank you.

Dr Nigel
2006-May-18, 12:34 PM
Very interesting.

I have one or two minor quibbles.

(1) Your comment above implies that Calder Hall was also a U-C-H2O, whereas it was, in fact, air-cooled (this was a part of the problem when the graphite caught fire - should they leave the cooling air supply on, fanning the fire but preventing meltdown, or switch it off, allowing the fire to burn itself out but increasing the risk of meltdown).

(2) I think some of your comments concerning the lasting effects are a bit optimistic. There are still parts of Europe (e.g. Cumbria, in north-west England) where there is sufficient Cs-137 contamination that dairy farmers are forbidden from selling their milk and are forced to rely on government subsidies. Even if the contamination poses no risk to the population, governments cannot allow it to enter the food supply because of the risk that it will become concentrated and hence pose a larger radiological risk.

Glom
2006-May-18, 06:00 PM
(1) Your comment above implies that Calder Hall was also a U-C-H2O, whereas it was, in fact, air-cooled (this was a part of the problem when the graphite caught fire - should they leave the cooling air supply on, fanning the fire but preventing meltdown, or switch it off, allowing the fire to burn itself out but increasing the risk of meltdown).

No, what I meant was that we knew about it before even the beginning of the commercial nuclear age.


(2) I think some of your comments concerning the lasting effects are a bit optimistic. There are still parts of Europe (e.g. Cumbria, in north-west England) where there is sufficient Cs-137 contamination that dairy farmers are forbidden from selling their milk and are forced to rely on government subsidies. Even if the contamination poses no risk to the population, governments cannot allow it to enter the food supply because of the risk that it will become concentrated and hence pose a larger radiological risk.

Cumbria wasn't hit that hard. Remember, regulatory procedures have enormous inertia. Just look at the lasting effects of the BSE scare.

Dr Nigel
2006-May-19, 03:21 PM
Cumbria wasn't hit that hard. Remember, regulatory procedures have enormous inertia. Just look at the lasting effects of the BSE scare.

Yes, Cumbria was at the tail end of the fallout cloud. So the rest of northern Europe would have been more heavily contaminated, yes?

BSE remains a hazard to be avoided as much as practicable. I work in the biopharmaceuticals industry, and we are legally obliged to ensure that all raw materials we use in manufacture are free from transmissable spongiform encephalopathies. So your point is what exactly?

As far as regulatory inertia goes, don't you think that, if the milk were safe to distribute, the farmers would be raising all kinds of fuss? And, by "safe" I mean "perceived to be safe by the public at large as well as in the judgement of the radiological protection profession".

So, I stand by my initial feeling that your comments about the Cs-137 contamination were and are optimistic. And I believe that impression to be justified.

Glom
2006-May-19, 05:13 PM
Yes, Cumbria was at the tail end of the fallout cloud. So the rest of northern Europe would have been more heavily contaminated, yes?

Well that's exaggerating. Cumbria got between 10 and 40kBq/mē. Most of Europe got off far less than that. Only areas of Austria, Switzerland and some large parts of Scandanavia got worse, excluding of course Belarus, Ukraine and Russia. So Cumbria did get hit more than average, but it was still not that hard.


So, I stand by my initial feeling that your comments about the Cs-137 contamination were and are optimistic. And I believe that impression to be justified.

My comments come straight from UNSCEAR and the Chernobyl Forum reports. Looking at what I said, I don't think I was being optimistic in the way you imply. I said that the food chain is far less vulnerable to contamination than it was and that is true. A fair chunk of the stuff has decayed and more has gotten out of reach by various means. I will add a note about this problem though. Any idea how long this ban will last or what the contamination of milk is like quantitatively?

Extravoice
2006-May-20, 12:26 AM
Interesting website you have, 777. I spent a few minutes and learned a few things.

While not a commercial accident, you may want to discuss the SL-1 accident of 1961. If I remember correctly, it was the first nuclear reactor accident that involved deaths.

Some info can be found here:

http://en.wikipedia.org/wiki/SL-1

Dr Nigel
2006-May-21, 08:06 AM
My comments come straight from UNSCEAR and the Chernobyl Forum reports. Looking at what I said, I don't think I was being optimistic in the way you imply. I said that the food chain is far less vulnerable to contamination than it was and that is true. A fair chunk of the stuff has decayed and more has gotten out of reach by various means. I will add a note about this problem though. Any idea how long this ban will last or what the contamination of milk is like quantitatively?

OK, so maybe I read more into your comments than was intended.

I don't have the reference for that news item, I'm afraid. I read it in New Scientist a year or so ago (that the ban was still in effect), but I don't keep them that long (they take up too much space, so they go into the recycling every three months or so).

Glom
2006-May-24, 04:00 PM
Dr Nigel, forgive my ineptitude, but I did a search of the DEFRA website and couldn't find any reference to a Cs contamination problem. Googling didn't reveal much either, although I did find this very good book (http://www.freeread.com/Nuclear/index.html) but that's besides the point. Do you have more for me to go on?