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Poll

Should Nuclear Fission power plants be shut down?

Yes
2 (33.3%)
No
3 (50%)
Heck yes, Radioactivity!
0 (0%)
Heck no, lots of power!
1 (16.7%)

Total Members Voted: 5

Author Topic: Nuclear Power plants  (Read 2472 times)

Offline Ben6789

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« on: 24/04/2007 16:53:15 »
People hear Nuclear Power and instantly think Radioactivity. And then think no, i wouldn't want that. Or they think Chernobyl.

Chernobyl was because poor equipment and bad personnel. And at least replace the current nuclear fission power plants, they are 30+ years old! If we let them grow to old because people don't want more fission power plants, it will end up like Chernobyl!

It's expensive, but it's better than dumping even more pollution into the air.


 

another_someone

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Nuclear Power plants
« Reply #1 on: 24/04/2007 17:44:20 »
Sorry, I am confused about your question.

The yes and no are straightforward enough - but Heck no, Radioactivity! seems to imply that we should definitely not shut it down because we rather like the radioactivity; while Heck yes, lots of power implies that we should shut it down because we really don't like all of this power.  Have you perchance phrased your question in the reverse sense that you have phrased your answers?
 

Offline Batroost

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« Reply #2 on: 24/04/2007 18:19:40 »
The real problem with Chernobyl (i.e the RBMK reactors) wasn't the construction or personnel - it was the inherent instabililty in the reactor.

The RBMKs are boiling water reactors that mix a graphite moderator with a water/steam coolant. Whilst this is fine in normal operation, sustained low power operation can lead to a strongly positive "void coefficient". This means that a small amount of boiling in the core increased reactivty, which in turn raised power, which in turn raised temperatures and caused more boiling. In other words the reactors can be unstable - they'd already seen this from a power fluctuation event at Ignalina (in Lithuania) though this information was never passed-on to the operators at Chernobyl.

The Chernobyl explosion was caused by a test at low power that had been delayed and then reconfigured without the staff understanding the risks. A slight increase in power caused a massive boiling of water in the core and a very large release of steam. Power rose so quickly that the fuel rods failed dropping hot fuel pellets into the coolant, with more steam (and then hydrogen) production. This 'steam explosion' was sufficient to blow the 2000 tonne lid off the reactor, and then air rushed in and the hot graphite and fuel was free to burn. With no containment building the radioactive fission products were spread into the environment.

Apart from some very early weapons material producing reactors, nobody else designs or operates reactors with this inherent instability. For example, PWRs (Pressurised Water Reactors) have very stroing negative void coefficients that stop the nuclear reaction very quickly - and hence drop the power level - in the event of boiling. This is because in a PWR (or BWR) the water acts as both moderator - slowing the neutrons down so that the chain reaction can proceed - and as the coolant. In an RBMK the moderator (graphite) was separate from the coolant (water). You have separate coolant/moderator in a Gas Cooled Reactor (e.g. the UK's AGRs) but then you don't have to worry about boiling as the coolent is already a a gas.

NB: I've simplified a bit - but you get the picture?
« Last Edit: 24/04/2007 18:39:27 by Batroost »
 

Offline Ben6789

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« Reply #3 on: 25/04/2007 13:11:23 »
Sorry, I am confused about your question.

The yes and no are straightforward enough - but Heck no, Radioactivity! seems to imply that we should definitely not shut it down because we rather like the radioactivity; while Heck yes, lots of power implies that we should shut it down because we really don't like all of this power.  Have you perchance phrased your question in the reverse sense that you have phrased your answers?

Crap, your right...screwed up again..
 

Offline Ben6789

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« Reply #4 on: 25/04/2007 13:13:18 »
The real problem with Chernobyl (i.e the RBMK reactors) wasn't the construction or personnel - it was the inherent instabililty in the reactor.

The RBMKs are boiling water reactors that mix a graphite moderator with a water/steam coolant. Whilst this is fine in normal operation, sustained low power operation can lead to a strongly positive "void coefficient". This means that a small amount of boiling in the core increased reactivty, which in turn raised power, which in turn raised temperatures and caused more boiling. In other words the reactors can be unstable - they'd already seen this from a power fluctuation event at Ignalina (in Lithuania) though this information was never passed-on to the operators at Chernobyl.

The Chernobyl explosion was caused by a test at low power that had been delayed and then reconfigured without the staff understanding the risks. A slight increase in power caused a massive boiling of water in the core and a very large release of steam. Power rose so quickly that the fuel rods failed dropping hot fuel pellets into the coolant, with more steam (and then hydrogen) production. This 'steam explosion' was sufficient to blow the 2000 tonne lid off the reactor, and then air rushed in and the hot graphite and fuel was free to burn. With no containment building the radioactive fission products were spread into the environment.

Apart from some very early weapons material producing reactors, nobody else designs or operates reactors with this inherent instability. For example, PWRs (Pressurised Water Reactors) have very stroing negative void coefficients that stop the nuclear reaction very quickly - and hence drop the power level - in the event of boiling. This is because in a PWR (or BWR) the water acts as both moderator - slowing the neutrons down so that the chain reaction can proceed - and as the coolant. In an RBMK the moderator (graphite) was separate from the coolant (water). You have separate coolant/moderator in a Gas Cooled Reactor (e.g. the UK's AGRs) but then you don't have to worry about boiling as the coolent is already a a gas.

NB: I've simplified a bit - but you get the picture?

Yes, i do. It's a bit clearer now.
 

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Nuclear Power plants
« Reply #4 on: 25/04/2007 13:13:18 »

 

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