How long will nuclear power last?

[Johan]

you know .. people never thought we'd run out of fuel and now we are !!

you never know .. we might run out of uranium too ... have you seen the population surge of the last century?

Well both sea water and plain old granite are viable sources of uranium, I don't think we will ever run out of granite.....

[Johan]

I notice that no-one mentioned thorium as a potential nuclear fuel. I'm quite pro-nuclear, but I have an extremely strong bias towards systems that are safe by design. I should also point out that I'm a programmer and that I came here to learn. Does anyone have any knowledge of reaction systems which don't employ the physics of critical mass?

You could specify some question about sub critical systems and I could try to answer. Note though that a sub critical system isn't inherently more safe than a critical system. Safety to a large extent depends on how one gets rid of decay heat from the system and that is a problem facing both sub critical and critical reactors.

[KitemanSA]

I notice that no-one mentioned thorium as a potential nuclear fuel. I'm quite pro-nuclear, but I have an extremely strong bias towards systems that are safe by design. I should also point out that I'm a programmer and that I came here to learn. Does anyone have any knowledge of reaction systems which don't employ the physics of critical mass?

Please be careful how you phrase your question. Your use of the term "critical mass" suggests you think in terms of bombs and the minimum mass (critical mass) for an explosion. Nothing could be further from the truth with nuclear power plants.

And taking your lead from your Thorium remark, I have determined that we have at least 500 million years worth of "accessible" Thorium here on earth. Any increase in the efficiency of extracting Th from granite would increase that by about 25%. Any new technology that would allow deeper mining could increase it a LOT.