A bike ride to Chernobyl

That's pretty spooky... The whole tone of that reminds me of what my mum saw when she went to Hiroshima - apparently there is no birdsong there and virtually nothing grows.

It makes you wander why they decided to test the freewheeling of the turbines in the first place; surely everyone knows that if you turn off the coolant pumps to a reactor, things tend to run away from you?

What a waste of life...

__________________________
Don't wanna be cremated or buried in a grave
Just dump me in a plastic bag and leave me on the pavement
A tribute to your modern world, your great society
I'm just another victim of your highrise fantasy!

Thanks for that interesting link Derek.

There's a film about Chernobyl called "Raspad", directed by Sergei Shakurov. It's very dark, obviously, but rather good.

ejt - you are welcome - I think that the website has had quite a bit of publicity recently - I picked it up from a newsgroup that I watch

Derek

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Fascinating.

Excellent. Thanks for that.

Her is a link to more horror stories from the Nuclear zone - more words this time and no pictures

Nuclear Waste

Derek

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How many of you were at the 46th Aldermaston March last weekend ?


Fritz Von Whiteman

quote:

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How many of you were at the 46th Aldermaston March last weekend ?

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I thought we where talking nuclear power here, not weapons?

Here in Sweden we have to be better than everybody else and has turned one perfectly okey nuclear power reactor of. When it's cold in the winter and our own electrical resources aren't enough, we instead imports power from one of Shernobyl's sister power plants.

JohanR

good thread, thanks

Wow, a website that's actually worth the bandwidth.

Great stuff.

-- Ian

In case any one is thinking that I am against nuclear power - I am not - I have concerns that the sensible and safe use of nuclear power is being abandoned as a result of hysterical dogma

The If program on the Beeb a few weeks ago really brought home the need for a sensible nuclear power program in the UK - there was a very good article on this forum a few months ago by a person involved in nuclear power that demonstrated the positives of a well planned nuclear power program.

Chernobyl was a disaster waiting to happen based on the configuaration of the site.

Derek

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Two thirds of electricity in France is generated by nuclear power, and afaik, we import some of it.



Regards,

Steve.

this is very true steven, great innit, as I mentioned many months afore, the green stuff too.luvvly jubbly.
Fritz Von Oppenheimer.

Weapons / Power. tell me the moral difference ?

Atoms for peace – the salvation of life as we know it

cheers

Nigel

quote:

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Weapons / Power. tell me the moral difference

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One has the purpose of killing people / The other is used to make life better, quite a big difference to me. I'm not strictly talking nuclear devices here, the comparasion can be made for conventional weapons / power sources to that happens to use the same type of fuel.

quote:

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The If program on the Beeb a few weeks ago really brought home the need for a sensible nuclear power program in the UK - there was a very good article on this forum a few months ago by a person involved in nuclear power that demonstrated the positives of a well planned nuclear power program.

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Actually, one of the political parties here in Sweden, the "Liberal" one, officially went public just a week ago with the notation that "We will have to build new nuclear power plants in the not to far future." It will happen.

JohanR

You mean like a bread knife ?


Fritz Von Deadlytoysltd

A very interesting article.

What a brave woman. I am not sure that I would want to ride through that area.

What makes this of all the more concern is that there are a number of Chernobyl-style reactors still running in the former East-Bloc countries. I understand that there is one not too far across the border from Vienna, for example.

If I remember correctly, at least one contract has been placed with a western company (German, IIRC) to retrofit improved monitoring and alarm systems to bring these reactors to western standard.

In my opinion, this is something of a forlorn hope. These water-cooled, graphite moderated reactors have what is known as a positive void coefficient of reactivity which makes them liable to explode. This is why this type of reactor was not selected for use in the UK. Instead, the UK developed its own gas-cooled, graphite moderated reactor system.

There are reasons why the Soviets chose this type of system: it's cheap, simple technology and by-the-way, with the correct fuelling strategy, quite good at producing Plutonium for weapons programme use. Not that I am suggesting that the majority were used that way.

As it's a slow day in the office, I would like to explain why this type of reactor is so dangerous.

In a chain reaction, neutrons are produced when the uranium nucleii split. These neutrons then go on to split other nucleii and so on. Energy (heat) is produced. (Actually this is not quite correct - a neutron hits a nucleus and it splits, it then fuses into two smaller nucleii (the fission products), it is this fusion, this falling to a lower energy state, which releases the energy and leaves a few neutrons over.)

Now here's the problem, the neutrons need to be slowed down before they can split another nucleus and we need to mop some of them up. So that one neutron splits a nucleus and only one neutron is left over to split the next. Energy is then produced at a nice steady level. As it is, after fission, more neutrons are produced than the one that did the splitting, if all these caused further fissions, the energy output would climb.

So how do we do this. Graphite is a moderator, this slows down the neutrons to thermal energy levels ready for the next fission. Water is the coolant but also absorbs neutrons. Good. So get the geometry right and the coolant, which you need to get the heat out to make steam to drive the turbines, doubles up as a neutron absorber.

Of course, you want to be able to ramp the power up when you start up and ramp it down when you shut down, you do this by moving neutron absorbing rods in and out of the core.

The reactor is a bit of a plumbers' nightmare I've heard. It must be very hard to avoid leaks.

So what happens if for some reason the temperature of the water rises? Well, it could boil, especially if a leak caused low water pressure. If it boils, we have a void in the coolant. Steam, being less dense than water, absorbs fewer neutrons, so more go on to cause fissions, hence the number of fissions starts to ramp up and with it the energy production and temperature. This, of course, causes more coolant boiling, less neutron absorption, more fission and so on. In a very short time, the temperature is so high that the reactor bursts and catches fire.

I cannot remember how fast the temperature can rise but I recall being surprised at how fast this type of reactor can run away. Of course, the safety system should spot the initial temperature rise. IIRC, the safety line at Chernobyl was bypassed for some reason. Again, IIRC, the Soviet reactors do not feature the multiple redundant safety systems we have in the west. Perhaps they do now.

Now that the Soviet era is at an end, it would be useful for the west to assist in the replacement of these reactors.

My information is a little out of date now, I used to work on reactor safety studies some years ago. I can only hope that work has been, and is being done, to make these reactors as safe as possible. Without work in this area it is hard to see how we can be confident that such an incident could not occur again.

Regards,

Paul.