Is nuclear fission safe?

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Thorium is a nifty fissile element. When it fissions it does not produce any plutonium as a by product. Also it is closer to lead so it will decompose to lead sooner than uranium does.

ruveyn

The element with the longest half-life of which I'm aware is iron. It barely decays at all.

It's not the length of the half-life you need to worry about - it's the energy of decay, and the decay products.

The bad thing about uranium is that it has both an excessively long half-life (of its by-products too) and they are extremely dangerous. The again, if someone were able to utilize nuclear fusion, the entire problem would be obsolete.

I thought that Thorium was abandoned because it's so difficult to make nuclear bombs from the byproducts.

Yodah says: Do not your breath hold until nuclear fusion practical is, else blue turn you will.

ruveyn

Believe it or not, the real obstacles to safe, fairly cheap (when compared to the true costs to our species/planet of current oil and coal consumption) disposal of nuclear waste happen to be the very environmentalists who actively prevent any rational scientific study of disposal of nuclear waste in space. This despite the fact that it is the ONLY currently viable alternative to the production and consumption of fossil fuels to meet our growing energy demands. While there are a number of valid concerns such as launch failures, they can certainly be minimized below the current risks from siting this waste on earth. And it is certainly less harmful to the planet than the huge atmospheric experiment we seem determined to run and hand off the consequences of to our children.

Before someone starts screaming about fallout should a rocket explode and create another Chernobyl like incident, I would suggest you look up the term vitrification and its uses in nuclear waste disposal. Chernobyl, Three Mile island, Fukushima and the rest occurred because of poor siting, poor construction, and poor operation of technology developed in the 50's and 60's of the LAST century. We can do so much better, but again the boogy man of radiation has otherwise rational people imitating chicken little and preventing any real debate.

Let's build the fission plants, shutter the coal burners, and shoot the waste into deep space or the sun. And if I hear someone yelling about polluting space, well, i'm not normally a violent person, but I have my limits ;-P

Umm, actually it depends on the materials being fused. The one they are experimenting most with is deuterium-tritium since it requires the least amount of energy in terms of ignition and mostly produces helium. The problem is that it also produces high energy neutrons. And while they hope to use the neutrons to breed more tritium (a very rare radioisotope of hydrogen) from blankets of lithium surrounding the reactor, the simple fact is that the high energy neutrons and fusion plasma will seriously erode the walls of the reactor as well as make those same walls highly radioactive. The expected lifetime of the reactor walls will most likely be measured in months before needing replacement, and then you have the same problem of disposing of highly radioactive waste.

Speaking of nuclear fusion, in 15 years we will have commercially viable technology, provided physicists don't get any surprises when they turn on ITER.

Pretty safe. The byproducts are nasty but nothing we can't cope with once we have developed proper processing methods (most of our current methods are rubbish). Safer than coal and oil anyway.

Thorium is much better than uranium but restricted in that we have to breed it into Uranium 233 which is then fissile. Thorium is not naturally fissile. You can do this by introducing a fissile element (U238/Pu239) or by introducing a source of neutrons (neutron spallation). Problem is that you need a much higher proton beam current than accelerators right now are capable of.

That's why China's still pushing in the direction of molten salt reactors.

Just thought I'd chip in. I'm a PhD physicist so if anyone wants to ask any questions about how this all works, feel free

Oh, as for the radiation question, water attenuates radiation really, really well. It absorbs alpha within a few cm, beta within 10-15cm and what little gamma is given off. The water itself will become excited over time but this energy is given off as heat, not generally as radiation. You will get a small amount of ionisation and excitation and some radioactivity within the water but the radioactive byproducts themselves are extremely short lived. Most of the contamination you see in a pool of water comes what little comes off the rods themselves through natural ablation.

I think it’s a safe bet we’ll be depending on nuclear fission for quite some time.

The half-life of protons is supposedly at least 10^21 years. I don't know if there is anything with a longer half life.

Nuclear power may not be 100% safe but it's safer than many other reliable source of energy.

From the Paul Scherrer Institute in Switzerland, as quoted in the environmentalist James Lovelock's 'Revenge of Gaia':

Fuel, Number of fatalities, Who dies?, Deaths per Terawatt-year:

Coal, 6400, workers, 342
Natural Gas, 1200, Workers & Public, 85
Hydro, 4000, Public, 883
Nuclear, 31, Workers, 8

This used data from energy producing industries from 1970-1992, so includes Chernobyl. Nuclear is thus a very safe form of electricity generation when compared to other methods. I think a rational energy policy would be based on nuclear for baseload (a disadvantage is it can't be turned on and off easily), natural gas for peak electricity generation, wind to displace gas where possible and economical (I disagree with Lovelock's opposition to wind power).

A lot of people see this with a lot of disbelief, as it challenges preconceived opinions, but one has to go with the facts.

As for the disposal of waste, a rather interesting idea bound to annoy the traditional environmentalist movement suggested by Lovelock is to dump it in the Amazon rainforest. Around Chernobyl, away from human interference wildlife is booming. Turns out the wildlife, although having an increased mortality rate, survives more than long enough to reproduce thus the benefits of no human interference outweigh the dangers of the radiation.

I think the only arguments against nuclear are economic ones, but that's for another discussion.

What is interesting about nuclear energy is the split between those in a panic about Global Warming. Some of them are ready to adopt nuclear energy as the cleanest real energy source available while others are against anything not involving solar or wind.

Wind energy is solar energy (of a kind). It is due to the Coriolis Force of the earth's rotation and the uneven heating of the air by the sun. The problem with photovoltaic and wind generation is lack of steady levels and the inability to store the energy for use at night. You will notice that during night time the sun's light is missing. Wind is slightly better. There are sections of the country near the ocean that have fairly steady winds. What they also have is rich Liberals who build their fancy houses on the sea cost and do not want their view of the ocean spoiled by wind mills.

ruveyn

This very thing happened in Canada... our beloved Anne Murray refused to have barely-visible white dots "ruining" hew view of the ocean so she led the charge to ban oceanic wind generators near her precious island.

You'd want wind generators where there's less bird/bat life... if they don't get chewed up by the blades themselves, their lungs explode if passing too near the negative air pressure generated behind them.

NO technology is currently perfect - they all have a negative side-effect. It's up to us to refine these technologies (or create an entirely new one) to reduce or eliminate these negatives.

Solar power is still inefficient and requires toxic elements to create the panels... but if it could be refined to the point of generating much more energy and not require any toxic elements at all, cheap like hell to make, they could be deployed all over the place and do extremely well. I'd love to see refinement/development there.


Of course, nuke plants are being refined at a faster rate - getting more energy per kilo of fuel, using a higher percentage of that fuel before it's "not powerful enough" to do the job (while still incredibly toxic) meaning less waste as well as producing a waste less toxic. That's not terrible either, but it still leaves the danger of catastrophic meltdown, whereas super-refined solar technology could have almost zero negatives other than having to deploy wide-scale so people would have to do it for themselves on the roofs of their homes (and the critical element there is, power companies would lose control of charging people money for their services!!) Money is the final word to any corporation... not humanity.

The cure for that is breeder reactors. Which not only make fissile fuel from non-fissile but also consume the radioactive "waste" that is currently discarded from non-breeder reactor planets. There is a catch. Breeder reactors are potentially more dangerous than light-water reactors and have to be managed very carefully.

ruveyn