Government and Nuclear Power...

gromituk

No, I don't disagree with you that the changes may not entirely be down to man.

What I don't understand is the relevance of this: we know we are pumping man-made CO2 into the atmosphere at a huge rate; by the same token, can we not conclude that what we are doing is dwarfing anything that might be happening naturally, and so we can change our consumption habits to do something about it.

We might not be 100% sure about this, but if we wait until we are, it will be too late - we need to do something now.

talksalot81

I am not for a moment suggesting that we just forget about it and move on, most definitely not. But I do think we need to keep our eyes on reality. There is alot more to the problem than CO2 and it is altogether feasible that we would be better sacrificing a little in the short term for a longer term gain.

This sideline was initially sparked in response to comments that we would be better off saving some CO2 in the short term (not building nuclear stations) and putting that 'saving' into something like wind turbines. I still think this is an altogether false economy. Firstly, I dont believe (give me a reference if I am wrong please) that the wind power bought with the CO2 'saving' can actually produce the necessary power and, in some ways more importantly, I see this as actually losing out in another way. You end up not really saving on the CO2 but now you have (at least what I consider) a visual scar on the environment. Which leads us once again to questioning the definition of damage to the environment.

Moggles_2

Originally posted by talksalot81
It is altogether feasible that we would be better sacrificing a little [CO2 saving] in the short term for a longer term gain.

Except that, in the case of nuclear fission, there is no longer term gain to be made.

It is misleading to suggest that nuclear power will reduce CO2 emissions. To generate electricity from uranium, a chain of industrial processes is needed to convert uranium ore in the ground into fuel elements for the reactor.

Usable uranium deposits are found in concentrations of about 0.01- 0.02 per cent (100-200g per tonne of rock). Around 98,000 tonnes of rock has to be mined and milled to give up one tonne of uranium. A standard 100mw/eh nuclear reactor requires in the region of 160 tonnes of uranium fuel, processed from around 16 million tonnes of rock every year. Mining uranium is not only dirty and uneconomic, but uses more energy to recover, than it will ultimately produce.

Remember this does not take into account the construction of the facilities including the nuclear power plant itself or the processes required to handle and store waste. All these processes produce substantial amounts of carbon dioxide as well.

You end up not really saving on the CO2 but now you have (at least what I consider) a visual scar on the environment.

An offshore wind turbine pays for itself, in terms of CO2 savings, within eight months. Photovoltaic [PV] modules can be an integral part of the building replacing conventional roof tiles. The visual intrusion of renewables matters less to most of us than the siting of a nuclear power station.

talksalot81

I would be very interested to hear where that value of 160 tonnes per year came from since it sounds unrealistically large. I'd also be interested to hear the source of your claim that:

Mining uranium is not only dirty and uneconomic, but uses more energy to recover, than it will ultimately produce

This will have been one of the most fundamental considerations during the earliest reactor construction. If you consider fusion, the reason it is not yet online is because it has only quite recently been brought to significantly 'breaking even'. That will, at least to some extent, have also been considered with fission. Furthermore, that was right at the start of fission. In the intervening time we have vast improvements in the efficiency of uranium production and vast improvements in the efficiency of 'energy extraction'. So to suggest that today we are making a net loss implies that, in the early days, the net loss would have been almost unimaginably large. A further point on this is that nuclear power is often driven by private industry. That means there is a profit which, as a rule, will not tend to follow when the core idea actually is suffering a loss.

Why should the siting of a nuclear station concern you more than the visual intrusion? Almost every nuclear power station has produced absolutely zero intrusion and zero consequence to people living near it. Thus the only reason for real concern is because people believe the media. As a physicist with a reasonable understanding, I would happily live and allow my family to live within close proximity to a nuclear power station. I most certainly would not say the same for many other of our existing fuel sources.

It still strikes me as significant that most of those against nuclear power are not specialists. It also strikes me that, within my field of physics colleagues, most do not share those fearful views.

Volcano

This will have been one of the most fundamental considerations during the earliest reactor construction.......... So to suggest that today we are making a net loss implies that, in the early days, the net loss would have been almost unimaginably large.

Initial reactors were constructed to produce plutonium for nuclear weapons, the economics of this would have been unimportant. I assume that electricity generation was initially a by-product of the excess heat generated, with the first commercial nuclear power station beginning in 1956.

I found an average figure of 152 tonnes of uranium per year from here:

http://www.opendemocracy.net/globalization-climate_change_debate/2587.jsp

And this site:http://www.zealllc.com/2005/uranium.htm

....says that of 180 million pounds (weight) of uranium consumed last year, 104 million came from mining (58%) which works out at 47,173 tonnes, divided by 440 worldwide reactors = around 107 tonnes per reactor per year on average. This figure of 107 tonnes per year is probably the most accurate as it relates to uranium from mining only.

talksalot81

My sums initally suggest that has to be a way off, but on recalculation I come to 100 tonnes being approx 1 TWhr output per year which actually is not unrealistic. So I stand corrected on the quantity thank you.

I was only referring to commercial power stations, not experimental reactors (hence my relating to fusion power which is currently at experimental stage). I find it exceptionally hard to believe that they started working at a huge loss and even harder to believe we would still have it if that remains to be the case. I havent done a search to find numbers for uranium production so cant give numbers, but it just doesnt make financial sense if there is an energy loss. Maybe someone else has good reliable numbers we can use as the basis for a calculation???

Moggles_2

Originally posted by talksalot81
I havent done a search to find numbers for uranium production so cant give numbers, but it just doesnt make financial sense if there is an energy loss.

You'll find these statistics and lots of others around page 8, if memory serves, of this doc::
http://www.peakoil.com/static/nuclearpower_facts.pdf

We can argue till the cows come home about the precise figures. The point is a nuclear power plant is not a stand-alone system. It's part of a long chain of industrial processes, which all consume fossil fuels. This is easily overlooked because the quarrying and disposal of the tailings takes place overseas or at least in areas remote from the power plant. Some other essential processes start only after the reactor puts its last kilowatt hour into the grid. The fact remains, each nuclear power plant leaves behind a substantial energy debt.