Nuclear Power

[twomers]

Hi all.

In university we're studying different types of power systems and generation methods and one of the more interesting types are nuclear stations.
I know where I stand on it but I'm curious as to what others think.

For, or against? Please specify why.

[Ene Uran]

Too much highly radioactive nuclear waste that will pollute this earth for thousands of years. There are nicer alternatives like wind, solar, and wave energy.

[twomers]

Sure there are but the alternatives are in no way as power dense as nuclear. You say it pollutes the earth for thousands of years, and to some degree you are right. But consider this:

Suppose you want a 1 GW power plant. If you're using conventional steam powered stations you're going to require about 3 million tonnes of coal (about 2.1 or so of oil), to generate this power and with that tonnes and tonnes of waste is put into the atmosphere (nasty ozone depleting and global warming stuff like sulphuf dioxide, carbon dioxide, thier monoxides etc).

With nuclear you need 15 tonnes of uranium (or less depending on which process you use), and 1 tonn of waste is outputted. Now the generation of this energy doesn't produce any of the nasty pollution that oil burning does. None of it. It's 'clean'. But what it does produce (while dangerously toxic), is easily confineable and while we can't destroy it we can bury it deep deep into the earth surrounded by layers of concrete and lead and steel which makes it ... for the sake of the arguement ... clean.

I know you mentioned clean energies but the thing is nuclear is cleaner than a lot of methods and all clean energy production (so lets compare like with like), but it does not approach the necessary power densities that are required for the population demands of now, and the future. Unfortunately only fossel fuels and nuclear do that.

[twomers]

Also the enviornmental impact of some clean energies (I'm thinking hydro), has spectacular enviornmental inpacts. Take for example the three gorges dam. 1.2 million people were relocated for that. Think of the Hoover dam. Sure it's in a desert but before and after photos show the extent of it.

[Ene Uran]

Why is power density so important? That only leads to ugly looking and dangerous high tension transmission lines all over!

Also, some of the highly radioactive waste is in the form of inert gases. Very difficult to contain for thousands of years!

I was not advocating hydro power (too limited), and read that Hoover Dam was built mostly for flood control.

[twomers]

>> That only leads to ugly looking and dangerous high tension transmission lines all over!
Nope. That's just power :)
Power density is the amount of utilisable power in a substance per unit mole of it. So the more power you can get from something the less you need. Uranium and plutonium (which can be used too), have astronomical power available (ideally 3*10^6 times that of coal, but in reality it's reduced to about 120-140 thousant times due to impurities and power losses in energy conversion).
It's like technology - the smaller it is the happier we are! We no longer need room-sized computers, for example. So why need 130,000 times the stuff to get the same?

[Ene Uran]

Thanks for clarifying power density!

I need to add geothermal and bio energy to my list of cleaner alternatives.

[Ene Uran]

The 15 tons of uranium you are talking about must be highly enriched uranium. The world's supply of this particualr isotope of uranium is very limited, as far as I read.

[twomers]

>> Also, some of the highly radioactive waste is in the form of inert gases. Very difficult to contain for thousands of years!

Well not so. You are right, of course, about the gasses, but they are confineable.
In nuclear power generation the core is sealed off from the outside completely and that's where the radioactive 'stuff' is put and made react. That stays in there for about a year and a half (depending on the process it could be more or less, but 18 months is generally a good marker), so it is only when someone is to replace the fuel that the outside is exposed to the inside of the core. However someone'd be pretty stupid just to open my hypothetical door and let it all out. There are precautionary measures after precautionary measures being taken to ensure the gasses do not leak. I believe the chamber is vacuumated, flushed again and again, all bad gasses and waste is collected and then kept under heavy water for 40 years (no exaggeration there, honest!), and then burried. The danger of it (lets not ignore it is dangerous), leads to extreme precautions.

[twomers]

>> The 15 tons of uranium you are talking about must be highly enriched uranium.
3% The particular isotope that we use for the more general purposes naturally occurs at 1% (but processes called fast-breeding reactors use pretty much the whole lot!), but it is enriched to 3% and then used.

>> The world's supply of this particualr isotope of uranium is very limited, as far as I read.
With current processes the current known sores of it should last about 150-200 years (a lot longer than oil), but if fast breeder reactors are used more the life span should increase by at least ten-fold.
Also, remember uranium is mined. So it's not as though we can't get more :) Plus about 2-5% (I can't remember the exact figure), of the waste can be processed again to extract more useful uranium and this process makes it less 'bad'.

>> wind, solar, and wave energy
Wind is good, very clean etc, but it is not reliable. It's power is as a function of the wind ... same with solar with the sun. Sure you have predominantly sunny and windy places which integrally have a steady theoretical generation rating but that doesn't mean that every day you're guaranteed to get the power you want! Some good days, some bad days. Wave is like (kinda), hydro. Well it depends on the setup really, but they can be modelled with very similar methods and equations.

>> I need to add geothermal and bio energy to my list of cleaner alternatives.
Unfortunately their respective power densities are not enough either. Sure they're clean. But not good enough at the end of the day.

>> and read that Hoover Dam was built mostly for flood control.
Yep. That's true. But still it produces 1.8 GW of energy. You can't argue that's not favourable. I was just stating some facts. A lot of people give out about visual pollution too, but I think that's a silly arguement.

[jbennet]

Burn more coal.

I hate windfarms. I live near some in scotland sometimes

There lovely countryside all around then oh no! look ! a bloody great big rusty, noisy windfarm spolining the view :(

and im pro nuclear. i live near some and im ok

[twomers]

A funny thing is that Ireland's government is against nuclear energy being produced in Ireland, but it doesn't mind importing it in (there's a proposed link from the UK to Ireland where power will be bought and some of that's bound to come from nuclear!).

[EnderX]

I stand in favor of the use of nuclear power. As stated, the other 'clean' energy sources aren't capable of holding the load. (I believe I saw something once stating that Solar, Wind, and Hydro together would be able to account for only a few percent of our current energy draw. And let us not forget that Hydro generally requires building dams across rivers[the poor fishies!], while Wind seems to be a bird-killer.)

Fossil fuels do have an admittedly negative impact at times, but within America, unless nuclear is permitted, they're really the only fuel source we have that can fill the current energy requirements. American energy policy regarding nuclear energy seems to have been shaped more by the movie 'The China Syndrome' than by anything available in the facts themselves.

And one last argument: One of the reasons I kept seeing in textbooks for the 'nuclear == BAD!' equation was that the waste would still be radioactive for long ages to come. Good! Despite all the alarmism, this means it's not going to cause the kind of problems everyone associates with radiation! Which one has the higher output-per-minute of radiation, the 1kg sample of a substance with a halflife measured in days, or the 1kg sample of a substance with a halflife measured in years? And from what I understand, the halflife values for most of the stuff that could be carried elsewhere is measured in millenia. I admit I'm no expert, but from what I've seen, the really nasty stuff is never supposed to leave the reactor.

[twomers]

>> American energy policy regarding nuclear energy seems to have been shaped more by the movie 'The China Syndrome' than by anything available in the facts themselves.

Not so. http://en.wikipedia.org/wiki/Three_Mile_Island Three mile island was a near nuclear disaster in the late 70's. The danger is very real but complete isolation from new and developing plants was stupid too. Safety has been increased dramatically by standard since then.

>> the really nasty stuff is never supposed to leave the reactor.
See uranium 238 is what is mined commonly, but that's now what we use in the reactions. We want another isotope - U235. The half life is measured in millenia (with 238), but in the reactor the process is speeded mega-fold up by firing neutrons at the atoms which slpit up and create a chain reaction locally within the core (which is controllable), which releases power. Some stuff might be left in the core, but as I stated earlier, after about a year and a half most of the 'good stuff', has already been utilised, so what's left is useless.

[jbennet]

Not so. Three mile island was a near nuclear disaster in the late 70's. The danger is very real but complete isolation from new and developing plants was stupid too. Safety has been increased dramatically by standard since then.

Do a google for the windscale accidents in the ukthere's a proposed link from the UK to Ireland where power will be bought and some of that's bound to come from nuclear!).

I think that existed in the past but the IRA blew it up

[twomers]

>> I think that existed in the past but the IRA blew it up
Haha. Correct. i'd forgotten about that. But I should have been more specific - between mainland UK at high voltage DC, not Northern Ireland. They're going to re-make that one since things between the north and republic are better now.

[jbennet]

Oh, i know theres one between scotland and N.I, but i dunno about Ireland.

http://en.wikipedia.org/wiki/HVDC_Moyle

[Ancient Dragon]

There is no reason why we can't ship nuclear wastes to the sun for safe destruction. Yes it will cost a lot, but probably cheaper than trying to safely store it here on earth for thousands of years.

[jasimp]

How about mars, we could dump it there. It is a lot closer and nothing lives there, as far as we know.

[lasher511]

Despite what most people think about nuclear waste with it pouring out of these places by the barrel loads thats not actually the case. In the average year a nuclear power plant will put out 1 ton of nuclear waste per 1 million people. For those of you who don't know 1 ton = 1m square of water. Water itself has a much lower atomic mass then that of nuclear waste meaning that you need a much smaller amount of nuclear waste then you do water to reach a ton. This means to get power to 1 million people for a year you are only looking at a reasonably small amount of waste.

For somewhere that only has a population of 20million like Australia and a massive uninhabitable area of desert nuclear power is a very realistic option for generating electricity.

The average wind turbine can produce enough energy to run about 500 homes for a year. This may sound impressive but when you think of how many turnbines you need to provide power for 1million people(assuming you have an average of 4 people to a home) you need around 500 wind turbines running constantly. That is alot of noise polution and alot more space wasted then what the nuclear waste would be taking up.

Solar power also comes up with similar figures as wind power.

I think at the very least for Australia all of these options would be more then suitable given the large amount of uninhabitable land that we have. However even if we were to put wind and solar farms in the middle of nowhere we would still have to get it to the major cities and towns somehow. With nuclear power however a power plant can be built anywhere which means that the waste simply has to be transported to where ever it is being disposed.