Is nuclear fission safe?

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I just got home so I'll have to start searching for proof of the basic principles of the transference of radiation in general, to water if possible.

If it wasn't possible to transfer radioactivity to another substance, there would be no such thing as low-grade contaminated tools, etc, and no such thing as fallout (which isn't falling bits of uranium, it's just plain DUST made radioactive by the reaction. According to your theories, the only thing that needs burying away is the spent rods themselves, yet the data shows the storage of millions of gallons of radioactive WATER (in one of the links) and tons of low-grade radioactive contaminated items such as tools, gloves and other PPE.

The claim is gammas don't do this, not that nothing does this. Betas wouldn't, but neutrons would, and as far as I can tell, alphas might, although I'm not sure they'd be moving fast enough.


Most of this is worry that something *might* be contaminated. I don't know all the procedures, but I'd be willing to bet that things like gloves are always discarded as potentially contaminated even though most of them aren't. Also, to be clear, contamination is not transmuting elements, it's having radioactive dust (for example) get on something.

But you just said radioactivity doesn't transfer itself to anything... what is radioactive dust? Microparticles of airborne uranium?

Probably neutrons; in the xkcd example the picture came from they talked about a piece of lethally radioactive piping that had been into the pool for several years.

http://en.wikipedia.org/wiki/Ocean_disposal_of_radioactive_waste

This one is oversimplified but applicable to the argument. I'll have to revisit this tomorrow - I'd rather play with my snazzy new video card.

With breeder reactors the waste problem is minimized.

ruveyn

Sorry but you are wrong on several points,

1. A stainless steel drum will last between 100 and 1000 years, the vast majority of the radioactivity in spent fuel or high level waste will decay away within the first 300 years. So the drum will provide containment during the most important early time. If you use a copper or bronze drum then you can get even longer isolation based on the drum alone.

2. The waste is in a very insoluble form, it is either in a borosilicate (pyrex) glass which is very slow to dissolve or as uranium dioxide. As long as oxygen is absent UO2 is more insoluble than pyrex glass. In most waste disposal plans the waste will go into deep holes which are full of oxygen free water. It will take about 1000000 years for the high level glass to dissolve, this will make sure that all the Pu-239, Am-241 and almost all fission products will have decayed before they can escape from the glass.

3. The waste drums are to be packed into holes in the rock, often these holes are packed with clay between the drum and the rock. Most radioisotopes will bind strongly to the clay, thus fixing them inside the waste store. So if anything escapes from the waste drum early then it is likely to be stuck like a fly on flypaper on the mineral surfaces.

The key thing in waste store design is to make sure that the waste is isolated for more time than is required for the waste to decay until the radioactivity is no longer a threat.

I have seen designs which offer about 1 million years worth of isolation which will work, it is better to drill a deep hole into hard rock than to drop the spent fuel and high level waste in the sea.

It can be very safe. If you understand the physics behind it, it is very possible to make a reactor where it is very hard to screw things up. At both Fukushima and Chernobyl, the accidents were a result of operators not following standard procedure for emergencies. Also in both cases, the reactors had design flaws. The reactor at Chernobyl apparently didn't have steam pressure relief values, and they used graphite for the control rods. Graphite was a bad idea, because it is a moderator, meaning it speeds up the reaction, and because it could catch fire.

In the case of Fukushima, they dumped sea water on the reactor core, which was very, very, very, very, very, very stupid, not only because seawater is very corrosive, but because seawater has contaminants that can be neutron activated, meaning they become radioactive. (Purified water cannot be neutron activated/become radioactive). And than the seawater had to be dumped back into the ocean because you have no where else to put it! One of my physics professors I had last semester said that it would have been better to let them it meltdown. He thinks the operators may have dumped the water on it the reactor to save the reactors, so as to save their own jobs (and the bottom line of the power company), rather than do the right thing and let them meltdown. Once they melted down, the nuclear reactions would have shut down, with the mess still contained in the buildings.

In water cooled reactors, like in the US, the purified water acts as both a moderator (speeding up the reactions, and maintaining it) and as a coolant. If the water is lost, the reactions is shutdown. The reason the reactor is still giving off heat is because the most radioactive by-products are still giving off heat, and decay for a little while. Because of this, in the normal operation of the reactor, when they replace the fuels rods with new ones, the old ones must go into a cooling pond so they don't melt, until the most radioactively active elements decay away. (This takes about maybe a year at the most, I think).

The main problems with nuclear are not engineering (those are solvable) they are political. All the nuclear waste in the United States would safely be stored in Yucca Mountain, if it weren't for politics. One, nobody wants it shipped through their state, even though they don't have anything to worry about, because the containers that nuclear waste is carried in is puncture and fire proofed. By keeping them at the nuclear reactor sites, where the the containers rust and deteriorate, there is an actually greater environmental problem.

You can build reactors that literally won't melt down, because it is made to be physically impossible! Modular reactors are the future of nuclear fission. Also, among several ways to deal with the nuclear waste, is to reprocess it (France and Japan do this), reuse it (use the heat coming off of it), deep burn (using high neutron flux tokamak fusion reactor) to get by-products that will decay within a hundred years.

No, it produces large amounts of toxic waste that will not decay for millions of years (making it, in all reasonableness, a permanent problem). This could be easily solved, however, if Radon was used as opposed to Uranium, which would make that waste decay into a stable, non-radioactive form in a matter of weeks instead of millions of years.

Radon is a gas and it is not useful for generated large amounts of heat.

ruveyn

There are still other materials that could be used. Uranium has the longest half-life ever.

Thorium is the best bet.

Isn't that rare?

No, thorium is more plentiful than uranium.

Hmmm must be some other "T" element I am thinking of. What is its half-life?

232.0380504 x 10^10 years (Thorium-232). In any case, its the half-life of the products of fission that we have to worry about, not the half-life of the fissile material.