Thirdly, the 'idea' that coal emits noticeable radioactivity is a myth from the 1960s/1970s.

Really? Skip down to table 2 - German coal may not contain a large amount of Uranium, but it does have Radon, Thorium, and Potassium. Please read this post that I wrote using the data from table 2 for US coal.

I seriously doubt there's no U-238 in German coal if there is Ra-226 since they're related via the decay chain, and Table 3 disputes the lack of U in German coal - the ash and slag contain up to 411 Bq/kg of Uranium that has to exist in the unburnt coal.

Even if we ignore the Uranium and go with just the average levels of Th and K, we get a total activity of 435 Bq/kg, which is ~3.5x the lowest US value detailed in my other post. That means 1 kg of average unburnt German coal contains 29 BEDs. When burnt in a 'new' plant (assuming the 1% up-the-flue rule) each burnt 3.45 kg of German coal results in 1 BED (banana equivalent dose, 15 Bq) out the stack. I don't have figures for German coal consumption/year, but that's still quite a lot of fissionable material going up the stack. The US alone emits a minimum of 11 tonnes of U and 2.7 tonnes of Th - that's 70.25 billion (10^9) BEDs best case and 7.025 trillion (10^12) BEDs worst case.

Mass-for-mass, average unburnt German coal is 4.35 times as radioactive as your average banana.

Is it noticeable? Certainly. Is it dangerous? Probably somewhat. Is it worth "The sky is falling" hysteria? No.

God, was I stupid - here's the citation you require. Table 2 and the other statements that I quoted are in this document.

1 banana equivalent dose is approximately 15 Bq. Table 2 of this document shows the radioactivity of the coal - let's use the lowest US figures. The note above table 2 says to multiply the U-238 value by 14 and the Th-232 by 10, and add those to the K-40. The results in 124 Bq/kg for US coal, and 1628 Bq/kg for Brazilian coal. That indicates that 1 kg of unburnt US coal is 8.22 BEDs. When burnt, between 1% and 10% of the ash escapes the scrubbers and is emitted into the environment directly (new vs old plants). Assuming that all of the radioactive elements are end up in the ash/slag and NOT directly put up the flue (as would be the case with gaseous radioactive elements such as Ra-226 and Ra-228), 12.1kg of coal when burnt and passed thru 'new plant' scrubbers results in 1 BED out the smokestack. With 850 million tonnes (850x10^9 kq) burned in the US in 2009, that resulted in 70.25 billion BEDs.

If you use the worst-case US figures and an old plant, you end up with 12320 Bq/kg, which is conveniently close to 100x the best-case numbers - 0.121 kg unburnt coal = 1 BED, and 7.025 trillion BEDs up the flue. Interestingly, 121g is close to the mass of the average banana at 150g, so unburnt US 'bad' coal is as radioactive as your average banana, mass-for-mass.

Interesting quotes:

If we apply the 1% up the stack rule, that means 11 tonnes of U and 2.7 tonnes of Th went out the stack - that's a lot of radioactivity up the flue and a lot of fissionable material wasted.

Please check my math.

... I want a stain-proof superhydrophobic shirt!

Bzzt.

Not even close - check out the cool antipodes map - the US is to the west of Australia and south of India. If you look closely, it seems that only a tiny speck of land in the south Pacific is antipodal to any part of the CONUS.

We already have compulsory education - it's only recently (that is, the last 20 years) that the backbone of that system has been ripped out by touchy-feely "we can't fail anyone - they're all special little snowflakes" and "we can't discipline your child - they're just asserting their independence" attitudes. I have no problem keeping students in school until they can pass some sort of minimum competency test or they're 21. I'm not sure what to do with them if they hit 21 and still can't pass the test - mandatory job training, I guess?

A friend of mine is of the attitude that anyone on government assistance of any sort shouldn't be allowed to vote - it's a conflict of interest.

The only guaranteed way to execute someone in a purely binary "either you're alive and in no pain or you're instantly dead" is to have them wear a C4-lined helmet. Even if only 1 of the many detonators goes off, all of the explosives will go. The shockwave is faster than nerve speed, so they couldn't feel pain.

My head just exploded. Excellent troll.

Because the PIV rating of LEDS will not withstand anything even close to full mains voltage. They are not constructed as rectifiers, even though they are technically diodes. This datasheet shows the max PIV for a high performance white LED to be a mere 5V! A typical 1N4007 rectifier diode is rated for 1000V PIV DC.

I've been in my new house for 6 years now, and I've replaced 4 incandescent bulbs, I think. These lights are used daily, and many of the ones still burning are turned on/off many times a day (bathroom lights).

I have an issue with LED and CFL that many don't - the electronics inside them (unless very well designed) make an absolute hash of radio bands from DC to about 30 MHz. As an amateur radio operator, I can't have that going on in my house (and preferably those houses around me).

I know the US Navy has performed experiments using lasers for submarine-to-surface comms - no idea on how well that went.

How much does a 300km spool of fiber optic cable weigh again? :-)

I wonder if sound would provide a very low bandwidth channel? If you can get good coupling into the ice ot should transmit sound relatively well.

... SLF radio repeaters ...

Why try to brute force RF down at the DC level? Why not head to the other end of the spectrum and use lasers? If that water is relatively pure and there are few bubbles in the ice, I think lasers would win the size/weight to comm distance race.

BTW I love the idea of a modulated neutrino beam, except how much mass would it take to even modulate it enough to be detected?

No current power generation use. It's used for medical lung imaging today.

In a word, Helium3.