Follow-up to last post

Well, I sent an email to some of my friends asking them to write letters, too, maybe hoping that well, enough voices might influence some third level aid and have some itty bitty effect. When Peter sent me this reply:

"Sorry, but I've heard that nuclear power generates nuclear waste, and even after processing it must lie underneath the ground for ~8000 years to become safe. Thus, I don't really trust nuclear power.

Care to convince me otherwise?"

I chose to follow up with this:


Inevitably it generates nuclear waste, but the problem is largely mitigated by breeder reactors. By using these, we can essentially tune the type of waste we would like. It is generally preferred to have short half-life products, which is primarily produced by breeder reactors (http://en.wikipedia.org/wiki/Fast_breeder_reactor ). The idea is it will lose essentially all of its radioactivity in a manageable time frame, thus having to be stored for a much reduced period of time. The standard nuclear waste has a half life on the order of 25,000 years. This isn’t particularly dangerous, if you consider the meaning of “half-life”. If you lived next to nuclear waste for say 75 years, you will absorb 1-.5^(75/25000) = 0.26 % of its total radiative output. Consider Tin-126, for example, with a half life of 2.3e5 years and a decay energy of 4.1 MeV. A LD-50 in 14 days dose for a 100 kg man (for a 126 g, or 1 mol sample) occurs after 3.7 hours, with 45 minute exposure being equivalent to 5% increase in cancer risk (1 Gray, or 1 J/kg). It is a particularly nasty by-product though, being 20-50 times worse than virtually every other byproduct with a shorter half life. A more representative isotope such as Pd-107 instead gives the same man about 9 mGy dose over an entire day – about the same as an abdominal CT scan (8 mGy). We can to some extent tailor products by choosing the reactions we use to generate energy, so we can make even these long-lived isotopes pretty safe inherently, in addition to the fact they’d be buried in a mountain. (Half life and sample products source http://en.wikipedia.org/wiki/Nuclear_waste#Physics )

Short half-life products are much worse during their toxic time, but have half lives between 5 and 90 years. The containers we have made have been theorized to have zero degredation from erosion for approximately a 10,000 year period and are furthermore tested by such means as crashing trains into them, dropping them from 10 m onto steel spikes, and underwater submersion to ensure integrity over long periods. This means the material is essentially guaranteed to stay sealed up for 100-2000 half lives, leaving less than 10^(-31) of its original mass left over. For reference, this is the equivalent of the sun reducing to a tenth of a kilogram! (HAH astro rocking the absurdly high exponents again) This may further be mitigated by new initiatives such as the LIFE project (http://www.contracostatimes.com/localnews/ci_10951822?nclick_check=1&forced=false) that recycle nuclear waste for further fission, further reducing half-lives.

Whew! Hopefully this sheds some light on why I’m not particularly concerned. Besides, look at the alternatives. The only two more efficient things are throwing matter into black holes and M/AM reactions. “Renewables” such as wind and hydro are essentially secondary solar effects; to power the US, the entire state of Connecticut (at 50% efficiency for 12 hours/day, storing half of that power for night-time use, with a nominal solar radiation of 500 W/m^2 at the equator. Area: ~ 14,000 km^2 or 14e9 m^2) would be needed to produce our current 3.5 TW of power usage. It’s simply not practical. To produce the world’s current 15 TW usage, we’d need about the equivalent of West Virginia coated in photovoltaics. Multiply as appropriate to accommodate for cloud cover and room for expansion (say, quadroupling it to account for it all) and you get every last square centimeter of *Texas* covered in photovoltaics. Again, plain and simple not practical. Wind and hydro both take more area to generate the same amount of power.

For other alternatives, “clean” coal isn’t, CNG is a carbon emitter and H_2 compresses so poorly that it takes as much or more fossil fuel burning to compress it as you save (simple PVNRT calcs). Finally, the P-P chain used in the sun (which is aneutronic) requires either solar compression or a temperature 10x hotter than the solar core. D-D and D-T fusion produces neutron side products, even when those neutrons are used to breed more tritium courtesy Li-6. H+B-11 can be used for aneutronic fusion, but power densities drop considerably and supersolar temperatures are still required; that is to say, the only realistic fusion will still generate radioactive byproducts. As a species and a country, we need to come to grips with the fact that to stop destroying planetary level ecology we have to accept geologically short to short-medium term storage of nuclear byproducts leading to extremely localized hot-spots. There’s simply not a good way around it.

I hope this, if not outright convinces you, at least puts a little doubt into your mind that maybe makes you see why, for example, Kit and I are both extremely pro-nuclear power.


Now, waiting for House to download ...