Ha se fosszilis, se alternatív energia nem jöhet számításba a jövő energiaigényének a kielégítésére, akkor marad a jó öreg atomenergia.

FREQUENTLY ASKED QUESTIONS ABOUT NUCLEAR ENERGY

"The basic fact about nuclear energy is that the input energy is 4.8 percent of output energy if gaseous diffusion is used to enrich uranium and 1.7 percent if the newer centrifuge technology is used. Another way of looking at the same facts is that if gaseous diffusion is used for enrichment, the energy invested in building the plant is paid back in 5 months, whereas if centrifuges are used the payback time is 4 months. "

"Perhaps energy scientists feel that mentioning nuclear energy will have an adverse effect on their grants. Perhaps there is some other reason. To some extent "hydrogen" in the energy literature is a code word for nuclear energy, since many articles promoting hydrogen don't say how else it can be generated economically in the quantities required to run an economy. "

How long will nuclear energy last?

"Nuclear energy, assuming breeder reactors, will last for several billion years, i.e. as long as the sun is in a state to support life on earth.

Here are the basic facts.

In 1983, uranium cost $40 per pound. The known uranium reserves at that price would suffice for light water reactors for a few tens of years. Since then more rich uranium deposits have been discovered including a very big one in Canada. At $40 per pound, uranium contributes about 0.2 cents per kwh to the cost of electricity. (Electricity retails between 5 cents and 10 cents per kwh in the U.S.)

Breeder reactors use uranium more than 100 times as efficiently as the current light water reactors. Hence much more expensive uranium can be used. At $1,000 per pound, uranium would contribute only 0.03 cents per kwh, i.e. less than one percent of the cost of electricity. At that price, the fuel cost would correspond to gasoline priced at half a cent per gallon.

How much uranium is available at $1,000 per pound?
There is plenty in the Conway granites of New England and in shales in Tennessee, but Cohen decided to concentrate on uranium extracted from seawater - presumably in order to keep the calculations simple and certain. Cohen (see the references in his article) considers it certain that uranium can be extracted from seawater at less than $1000 per pound and considers $200-400 per pound the best estimate.

In terms of fuel cost per million BTU, he gives (uranium at $400 per pound 1.1 cents , coal $1.25, OPEC oil $5.70, natural gas $3-4.)

How much uranium is there in seawater?
Seawater contains 3.3x10^(-9) (3.3 parts per billion) of uranium, so the 1.4x10^18 tonne of seawater contains 4.6x10^9 tonne of uranium. All the world's electricity usage, 650GWe could therefore be supplied by the uranium in seawater for 7 million years.

However, rivers bring more uranium into the sea all the time, in fact 3.2x10^4 tonne per year.

Cohen calculates that we could take 16,000 tonne per year of uranium from seawater, which would supply 25 times the world's present electricity usage and twice the world's present total energy consumption. He argues that given the geological cycles of erosion, subduction and uplift, the supply would last for 5 billion years with a withdrawal rate of 6,500 tonne per year. The crust contains 6.5x10^13 tonne of uranium.
He comments that lasting 5 billion years, i.e. longer than the sun will support life on earth, should cause uranium to be considered a renewable resource.
Here's a Japanese site discussing extracting uranium from seawater.
Comments:

Cohen neglects decay of the uranium. Since uranium has a half-life of 4.46 billion years, about half will have decayed by his postulated 5 billion years.
He didn't mention thorium, also usable in breeders. There is 4 times as much in the earth's crust as there is uranium. There's less thorium in seawater than there is uranium.
He did mention fusion, but remarks that it hasn't been developed yet. He has certainly provided us plenty of time to develop it. "

WHAT IF ALL ENERGY WERE NUCLEAR
Costs:

"The $2 billion estimate came from a recent Canadian proposal to build a reactor in Indonesia. American reactors that were delayed a long time for regulatory reasons have cost much more, but we can assume that the regulations will become stable worldwide. We can also expect that if reactors are built on the scale postulated, costs will come down a lot from experience. Indeed they may approach the low levels anticipated when nuclear power was first proposed. Perhaps we should consider $1 billion per 1,000 megawatt reactor as a likely cost."