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Is Uranium based nuclear power really all that dangerous?

Labarbapostiza

I was raised to believe that if a nuclear reactor had a meltdown, vast areas would be contaminated with radiation and uninhabitable. And we would all die.

But. Is this stuff really all that dangerous at all.

If you see photos of guys working with yellow cake uranium, they wear little protection and they don't apparently die from exposure. Yellow cake is about 0.7% fissile uranium. Enriched Uranium for power production is only between 2 to 5%.

If I were to construct a reactor with a few kilos of uranium, for home use, under my house.....Would it be any more dangerous than living in many parts of Ireland where there's lots of granite.

Are the fears of this power source more based on public ignorance than actual risk?

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Labarbapostiza

You see......I've had this idea.

Get some uranium, not particularly important the form. Flatten into sheets for greater surface/cross-section area. Then use tap water as a neutron moderator. And viola, I might have enough energy to run a home.

Maximus Alexander

My understanding is that yellowcake is mostly U-238 which has a half-life of close to the age of the Earth, this makes it barely radioactive and not particularly dangerous in this regard, but also close to useless for energy production unless it is enriched. It is highly toxic though and this, in addition to the alpha radiation that it does emit, makes it very dangerous if ingested.

I was interested enough to do some reading on this though after I read your post and it seems that without enriching it, you'd need to use heavy water as a neutron moderator to create a reactor, and a heavy water reactor doesn't seem like something you'd be able to build in your garden. Also, such a reactor is a source weapons grade plutonium, so... that's a problem too.

Then you have to deal with a world where these highly toxic, alpha emitting substances are widespread and accessible to the populace. Drop some plutonium powder in to a conventional bomb and suddenly you have an extremely dangerous weapon that can easily cause cancer in huge numbers of people.

Surely it would be a better idea to just lobby the government to start building actual nuclear power plants.

Labarbapostiza

Maximus Alexander wrote: »

My understanding is that yellowcake is mostly U-238 which has a half-life of close to the age of the Earth, this makes it barely radioactive and not particularly dangerous in this regard, but also close to useless for energy production unless it is enriched. It is highly toxic though and this, in addition to the alpha radiation that it does emit, makes it very dangerous if ingested.

Yes, but in the natural occurring Uranium, 0.72% is the 235 isotope which is less stable. The enriched uranium used in power is only enriched to 2 to 5%.

As far as I can see, two tons of enriched uranium, is only as risky a material as two tons of yellow cake.

I was interested enough to do some reading on this though after I read your post and it seems that without enriching it, you'd need to use heavy water as a neutron moderator to create a reactor, and a heavy water reactor doesn't seem like something you'd be able to build in your garden. Also, such a reactor is a source weapons grade plutonium, so... that's a problem too.

Deuterium, in the form of heavy water is something that can be bought by the gallon these days. But, I think you could just use tap water. You also use other things like graphite, maybe charcoal.

The water slows down neutrons from the 235 decay, the slower they move the more likely they are to enter other nuclei and cause a decay, than just rebound if moving too fast.

What your trying to do is get a density of decays, that's higher than the natural decay, you do this with a greater density of slow neutrons. With yellow cake, there isn't a ready neutron moderator in the material. But, in Richard Feynman's autobiography, he tells the story of visiting the Savannah Georgia processing plant, and finding uranium in some form stored near barrels of water. He says just the water would increase the decay of the uranium by a factor of 10............So...hey, i might just be able to use tap water.

Then you have to deal with a world where these highly toxic, alpha emitting substances are widespread and accessible to the populace. Drop some plutonium powder in to a conventional bomb and suddenly you have an extremely dangerous weapon that can easily cause cancer in huge numbers of people.

How much plutonium powder?.......These materials are only really hazardous in a concentrated state. A "dirty bomb" would disperse the powder. if it's dispersed enough, it's radiation isn't much more dangerous than natural background.

The "dirty bomb" is more fiction than anything else.

Any emission of radiation from a reactor can be stopped with a reasonable amount of shielding. I'm not sure where the reactor is, but a large research reactor I've seen on Youtube, the top is open, but the reagents are covered by water, but you can see down into the water and see the blue light Cherenekov radiation, from the neutron/water collisions. Water is good shielding.

Surely it would be a better idea to just lobby the government to start building actual nuclear power plants.

There are multiple issues that make that problematic. Years ago I think in the 90s, there was a national panic that there was a small research reactor in the basement of UCC.

What they were trying to do in Chernobyl was produce plutonium for bomb production. And they had Homer Simpson on the controls.

I think the overall design of the power plants has always been a case of excessive safety in the wrong places, then daredevil approaches in other areas (like using a potassium/sodium coolant mix - you will have an explosion). I think the first big Sellafield screw up was carbon moderator casings catching fire. (The problem there, if they didn't put out the fire, radioactive material would have been carried up in ash and soot). A "fail safe" reactor (something that fails safely), would probably be something where the moderator can drain, and the reaction stops.

Del2005

All well and good till you want to decommission it and have to deal with all the highly radioactive materials which remain. Where are you going to safely dispose of this material from your reactor, since most government's still haven't figured out what to do with this waste yet?

Labarbapostiza

Del2005 wrote: »

All well and good till you want to decommission it and have to deal with all the highly radioactive materials which remain. Where are you going to safely dispose of this material from your reactor, since most government's still haven't figured out what to do with this waste yet?

I was going to dig a tunnel, under my neighbor's house. Place the waste there, then concrete in my end of the tunnel.

The problem of disposing of the waste is more of a public relations issue. There's radioactive material everywhere. Even our food is radioactive (the law on alcohol in the US is it must be radioactive to be fit for human consumption - this is to stop the use of mineral alcohol, petroleum byproduct. The radiation in food comes from carbon 14, which produced by cosmic rays). Millions of tons of uranium bubble up from the crust into our seas and rivers every year.

Kranks whip up hysteria. This has made the disposal of the waste ruinously expensive. Coal fired stations also spew out lots of radioactive waste. There are other worrying issues around the proliferation of nuclear weapons.

The point I'm raising is, this may not be a dirty kind of fuel at all.

Del2005

Labarbapostiza wrote: »

I was going to dig a tunnel, under my neighbor's house. Place the waste there, then concrete in my end of the tunnel.

The problem of disposing of the waste is more of a public relations issue. There's radioactive material everywhere. Even our food is radioactive (the law on alcohol in the US is it must be radioactive to be fit for human consumption - this is to stop the use of mineral alcohol, petroleum byproduct. The radiation in food comes from carbon 14, which produced by cosmic rays). Millions of tons of uranium bubble up from the crust into our seas and rivers every year.

Kranks whip up hysteria. This has made the disposal of the waste ruinously expensive. Coal fired stations also spew out lots of radioactive waste. There are other worrying issues around the proliferation of nuclear weapons.

The point I'm raising is, this may not be a dirty kind of fuel at all.

The radioactive waste from coal and the radioactive waste from a decommissioned nuclear power station are slightly different. Yes the Soviets had a bad design in Chernobyl but the firefighters who dealt with the fire did get serious radiation exposure and the millions spend on robotics in other nuclear stations isn't because of hysteria. It's not a dirty fuel but it does create a lot of highly radioactive material which needs to be safely disposed of after use.

Labarbapostiza

Del2005 wrote: »

The radioactive waste from coal and the radioactive waste from a decommissioned nuclear power station are slightly different.

Well yes. But there is an issue, where the public perceives man made radioactive material to be far more hazardous than natural. A bit like the perception that natural "mineral" water is superior to processed tap water. The minerals in "mineral" water, straight from the ground, tend to be things like lead, and even uranium. (What you purchase, labelled "mineral" water, is in fact tap water.)

Yes the Soviets had a bad design in Chernobyl but the firefighters who dealt with the fire did get serious radiation exposure and the millions spend on robotics in other nuclear stations isn't because of hysteria.

I think over a hundred died fighting the fire. And I believe their radiation poisoning was the result of short lived isotopes. They're short lived so they have a higher decay rate, making them very dangerous over a short period, but conversely less danger over the long term as they decay so quickly.

It's not a dirty fuel but it does create a lot of highly radioactive material which needs to be safely disposed of after use.

This goes back to my original point (even though I made a little slip on the maths). If unenriched uranium, is only 0.72% 235, and enriched only 2 to 5%, by volume the enriched isn't much more of a problem in terms of radio-toxicity, than the unenriched. Dumping used uranium, i would be far more worried about the chemical toxicity than the radio.

For the short lived isotopes, a swimming pool is good enough storage, until they become less active.