[spynxic]

> Its fuel is also renewable because uranium dissolved in seawater will replenish through erosion faster than we could ever use it for billions of years.

It's been an hour and still no one's caught this but.. what exactly is this you're referring to? It'd be a fishy looking stoichiometric ratio if the fuel is produced from the seawater.

[acidburnNSA]

Good catch! This is a pretty epic idea but it is defensible. Here I quote from a paper linked below:

"One additional aspect of nuclear sustainability—noted long-since by Bernard Cohen—is that a significant fraction of the nuclear fission energy resource is in fact completely “renewable” in the same sense as wind and solar energy [32]. Wind and rain constantly erode the Earth’s crust, which contains an average uranium concentration of 3 parts per million. Rivers then carry this dissolved uranium into the oceans, at a rate of approximately 10,000 MT per year [33]. In a breeder reactor energy system, this is a sufficient rate to supply the world’s entire electricity demand at the present time more than five times over—or is roughly one quarter of what’s needed to supply a continual 100 TW to a hypothetical global civilization of 10 billion persons which is energy supply-replete by any contemporary measure.

As the crust is being eroded by rivers, it is constantly replaced by new layers of rock being pushed upward by plate tectonic processes. The supply of uranium in the Earth’s crust is effectively inexhaustible, on the order of 40 trillion metric tonnes, a factor of 10,000 more than is present in the oceans. At present erosion rates, this source of uranium would last on the order of 4 billion years, similar to the timespan over which the Sun will become a red giant.

Therefore, this assured source of “continually mined-by-Nature and oceanically presented” uranium will last as long as life on Earth does—even if burned at rates sufficient to supply a large fraction of a fully-developed human civilization—and represents an astronomical amount of nuclear energy, one that is in fact truly renewable and inexhaustible by any human measures."

[1] http://www.mdpi.com/2071-1050/4/11/3088/htm

[sbierwagen]

Note that uranium mined from seawater is about six times as expensive as conventional uranium: https://en.wikipedia.org/wiki/Brine_mining#Uranium

[acidburnNSA]

Indeed, which is why it's not done commercially today. Note also that total fuel cost is about 5% of the cost of a nuclear plant, and that includes mining, milling, enrichment, and fabrication. As seawater extraction becomes cheaper and uranium mines run low (no time soon), it will basically be a wash economically to switch to the renewable uranium. Also, breeder reactors don't need you to enrich the fuel, so that counterbalances any increased extraction cost. On the downside most (but not all) breeders require chemical reprocessing which so far has been very expensive. With development this too could go down.

The key point is that we would never run out of fuel as a species if we went big with nuclear.