Safe Storage of Nuclear Waste

[baywax]

What's the safest way to dispose of and store nuclear waste? Is there any chance of rocketing it into the sun or is it too heavy?

 

[Astronuc]

It costs about >$1000/kg (maybe closer to 10 times that) to lauch material from Earth to space, and that is just to orbit. That's more than the cost the energy extracted from the fuel. It's better to bury it on earth.

Handling high level waste requires heavy shielding, and so there is the mass of fuel + mass of shielding to consider.

It would never get to the sun since at some point it would melt/vaporize and then ride the solar wind back out into the solar system.

 

[chroot]

Launch vehicles explode all the time. You probably don't want a rocket full of nuclear waste blowing up ten miles off the ground, say.

And also, yes, it's very heavy, and there's a lot of it. It'd be incredibly expensive to launch this kind of material into space. In fact, it'd be so expensive that nuclear power would no longer be economical at all.

- Warren

 

[baywax]

It costs about >$1000/kg (maybe closer to 10 times that) to lauch material from Earth to space, and that is just to orbit. That's more than the cost the energy extracted from the fuel. It's better to bury it on earth.

Handling high level waste requires heavy shielding, and so there is the mass of fuel + mass of shielding to consider.

It would never get to the sun since at some point it would melt/vaporize and then ride the solar wind back out into the solar system.

So that would pose a risk of contamination to our planet and others. Plus, we'd all be too broke to do anything about it after paying for the "payload".

What are the alternatives?

Are there any reactive means of neutralizing the waste so that it doesn't pose a problem to future generations. Is there some process whereby the radiation is neutralized?

PS. I see Futuredreamz has a thread about turning waste into electricity. Sorry if this thread somewhat duplicates some of the entries there.

 

[Astronuc]

It would be prohibitively expensive to launch waste into space.

At the moment, there are those who support reprocessing of spent fuel in order to recover the unused U, Pu and transuranics, and separate the fission products, which are then vitrified and melted into a synthetic rock (which is geologically stable). The waste in solid form would be buried.

The most radioactive components decay in seconds, minutes, hours, days, weeks, months, . . . . up to years. The more radioactive a substance is, the faster it decays. The fast decaying products become inert quickly and further entrain the long-lived radionuclides. There is some thought that valuble isotopes would be recovered some time later in the future.

 

[daveb]

Right now it's also more expensive to design and build (and possibly even operate) a reprocessing facility than it is to use uranium ore to make new fuel.

 

[baywax]

Right now it's also more expensive to design and build (and possibly even operate) a reprocessing facility than it is to use uranium ore to make new fuel.

Yes, I thought the whole process of embedding spent fuel into artificial rock seemed time consuming and expensive.

Another by-product of nuclear power is heated water. When its discharged back into the river, stream or other source from which it is extracted, it upsets the balance of the original temperatures normally found in the source and thus creates an adverse condition for the flora and fauna of that source. Are there steps being taken to cool the discharged water to its original temp. and cease this infringement on the environment of the water ways?

Another question is: is there any contamination to the cooling system that may be discharged back into the water source?

 

[Azael]

Yes, I thought the whole process of embedding spent fuel into artificial rock seemed time consuming and expensive.

Its not very expensive, in sweden the construction and operation of the waste storage (not constructed yet) and all research is funded by a small fee on electricity produced by nuclear power and the fee is insignificant compared to other taxes ect.

Another by-product of nuclear power is heated water. When its discharged back into the river, stream or other source from which it is extracted, it upsets the balance of the original temperatures normally found in the source and thus creates an adverse condition for the flora and fauna of that source. Are there steps being taken to cool the discharged water to its original temp. and cease this infringement on the environment of the water ways?

Another question is: is there any contamination to the cooling system that may be discharged back into the water source?

The heating can be positiv aswell, seals are really thriving around the water discharge in sweden. If the discharge is straight into the sea the effect is quite small and very local. The temperature difference compared to the rest of the sea is located within a few square km.

You can get around it by using cooling towers or creating a artificial lake where the water can cool before going back into the river if river water is used.

But the waste heat can be used for district heating if the power plant is close to a major city.

 

[baywax]

Its not very expensive, in sweden the construction and operation of the waste storage (not constructed yet) and all research is funded by a small fee on electricity produced by nuclear power and the fee is insignificant compared to other taxes ect.



The heating can be positiv aswell, seals are really thriving around the water discharge in sweden. If the discharge is straight into the sea the effect is quite small and very local. The temperature difference compared to the rest of the sea is located within a few square km.

You can get around it by using cooling towers or creating a artificial lake where the water can cool before going back into the river if river water is used.

But the waste heat can be used for district heating if the power plant is close to a major city.

Thank you Azael,

Is there any radiation or other contamination to the waste water (other than heat)?

 

[vanesch]

Thank you Azael,

Is there any radiation or other contamination to the waste water (other than heat)?

Normally not: the cooling cycle is the 3rd water cycle in a PWR plant. The first water cycle is the one of the reactor vessel (closed circuit, can possibly be contaminated a bit by leakage in fuel rods, which itself is normally not the case). The second cycle is the steam/water Rankine cycle (also closed), normally not in contact with radiactive stuff, it is only in the exceptional case of a failure of the steam generator (the heat exchanger between the first cycle and the second cycle) that some first-cycle water can get into the second cycle.

The condenser of the second cycle is cooled by the third circuit, which is the external cooling water. It gets normally never ever in contact with any radiation or radioactive contamination, as it cools, through a heat exchanger, water which itself is normally not contaminated (and even if it were, by an accident, it is still separated from it in the condenser).

If however, there is a use of cooling towers, there might be the need to add some chlorine to the cooling water (which will be largely, but not entirely recuperated before dumping) in order to avoid legionella bacterial growth. In that case, there will be a small chemical contamination with some chlorine.

 

[vanesch]

What's the safest way to dispose of and store nuclear waste?

Bury it. That's now more than 25 years that one knows that this is a good solution, and one is still studying all kinds of exotic chemistry and other transport phenomena to find out whether really there's nothing overlooked.

You have to know that most of the activity is over in about 300-400 years (the fission products). One thinks that the human containment will hold it out for a few hundred years (stainless steel vessels and glass). Then it takes about 10 000 years to get rid of the minor actinides, which seem, however, not to get transported easily. Finally, if one were so stupid as to burry the plutonium too, you'd have to wait for about 100 000 years for it to fall back on natural radiation levels of uranium ore. But plutonium too, doesn't get transported easily.

Of course, you cannot bury it just anywhere, you have to study the geology very carefully, because the last thing you want is to put it in streaming ground water which would be too good a transportation vector. Clay layers seem to be very fit for the purpose, as they form a chemical barrier for actinide transport. Also salt depositions seem ok. Granite has an advantage (it is geologically extremely stable), but also a disadvantage (there can be cracks through which groundwater flows).

That said, there is no hurry, because nuclear waste is, on an industrial scale, relatively small volume, so storing it temporarily (even if it is for 50 years or more) is not a big problem - it even makes the underground storage simpler, as the produced heat and radiation will decay seriously over that time. Moreover, especially for "waste" from an open cycle, one might consider keeping it to reprocess later, as it still contains a lot of energetic stuff (95% of it, in fact).
It also gives more time to make one even more sure that the repository is going to be ok.

 

[Azael]

Its very interesting to read about the natural reactors in Oklo that ran 2 billion years ago and the transport of different radionuclides from the reactor area. Even there with extreme conditions and no protection whatsoever all the actinides and the long lived fission products have stayed within a few meters from the reactor zones.

 

[baywax]

Its very interesting to read about the natural reactors in Oklo that ran 2 billion years ago and the transport of different radionuclides from the reactor area. Even there with extreme conditions and no protection whatsoever all the actinides and the long lived fission products have stayed within a few meters from the reactor zones.

What happened with Chernobyl? How did the radiation from that accident spread? I know there were fires. Was it in the smoke and particles? There were maps showing the spread of the contamination to neighbouring countries. Not sure what happened there, the whole town basically died around that site.

 

[baywax]

Bury it. That's now more than 25 years that one knows that this is a good solution, and one is still studying all kinds of exotic chemistry and other transport phenomena to find out whether really there's nothing overlooked.

You have to know that most of the activity is over in about 300-400 years (the fission products). One thinks that the human containment will hold it out for a few hundred years (stainless steel vessels and glass). Then it takes about 10 000 years to get rid of the minor actinides, which seem, however, not to get transported easily. Finally, if one were so stupid as to burry the plutonium too, you'd have to wait for about 100 000 years for it to fall back on natural radiation levels of uranium ore. But plutonium too, doesn't get transported easily.

Of course, you cannot bury it just anywhere, you have to study the geology very carefully, because the last thing you want is to put it in streaming ground water which would be too good a transportation vector. Clay layers seem to be very fit for the purpose, as they form a chemical barrier for actinide transport. Also salt depositions seem ok. Granite has an advantage (it is geologically extremely stable), but also a disadvantage (there can be cracks through which groundwater flows).

That said, there is no hurry, because nuclear waste is, on an industrial scale, relatively small volume, so storing it temporarily (even if it is for 50 years or more) is not a big problem - it even makes the underground storage simpler, as the produced heat and radiation will decay seriously over that time. Moreover, especially for "waste" from an open cycle, one might consider keeping it to reprocess later, as it still contains a lot of energetic stuff (95% of it, in fact).
It also gives more time to make one even more sure that the repository is going to be ok.

Hi vanesch, Thank you for your info. Why can't we bury spent plutonium and what do we do with it these days? Is that classified info!?

 

[Azael]

What happened with Chernobyl? How did the radiation from that accident spread? I know there were fires. Was it in the smoke and particles? There were maps showing the spread of the contamination to neighbouring countries. Not sure what happened there, the whole town basically died around that site.

The radionuclides that was spread from Chernobyl was the chemicaly volatile ones. Iodine, cesium ect and gases like Xenon. Se this list http://www.nea.fr/html/rp/chernobyl/c02.html
If you look at the half lifes of the isotopes that did escape the reactor most of them decay away in a few days. They are not a problem in a used fuel repository since they decay long before they are placed there.

Not much of the actinides(the group of elements that uranium, plutonium ect belongs to) spread from the reactor.

Hi vanesch, Thank you for your info. Why can't we bury spent plutonium and what do we do with it these days? Is that classified info!?

Plutonium can be safely stored without a problem. But plutonium is very good reactor fuel and its wastefull to burry it.

 

[vanesch]

Hi vanesch, Thank you for your info. Why can't we bury spent plutonium and what do we do with it these days? Is that classified info!?

The good way to use plutonium is in fast reactors: it is a very good fuel. For the moment, in certain countries (France, UK,...) one is reprocessing the spend fuel and one extracts the plutonium. In others (Sweden, USA,...) one uses the "open cycle", that is, one considers the spend fuel as waste (which is very wasteful of ressources, but economically for the moment still viable).

Now, plutonium has several problems. It is by far the longest-living nuisible actinide, so in the waste, one counts on 100 000 years for it to take on "background" levels. This is not a problem by itself, but it would be better if this time were limited to 10 000 years of course, which is the case of spend fuel of which the plutonium has been removed but still contains the minor actinides (Np, Am, Cm), simply because the migration models have less uncertainties over 10 000 years than over 100 000 years. So one can put smaller error bars on the predictions of the safety of a repository over 10 000 years than over 100 000 years.
Moreover, plutonium is of course military a sensitive material, although this is over-emphasised: the plutonium from thermal power plants is of such an isotopic composition that it is difficult (although not impossible) to use to make a nuclear weapon.

All these are good reasons on the "waste" side to remove the plutonium. On the "fuel" side, as Azael said, plutonium is a "good fuel", but one has to put a caveat here. It is the perfect fuel for a fast reactor. But in a standard PWR, it is problematic. One can partially reuse it in so-called MOX fuel, but the difficulty is that in a thermal spectrum, the "good" plutonium Pu-239 can fission, but also absorb a neutron to form Pu-240, and so on, which absorps neutrons, which is highly active, and which ends up becoming Pu-241 which decays into Am-241, a nuisance.

So as long as we have a park of just PWR or BWR with thermal spectrum, we have only a limited possibility to re-use the plutonium. The plutonium from used MOX fuel is so good as unusable in a thermal (water) reactor, and will end up producing a lot of minor actinides. The gain in "waste" this way is limited, and the gain in fuel also (about 10-20% economy in fuel).

Genuine plutonium recycling only really makes sense if we have in the park of reactors, also a certain fraction of fast reactors. They can "eat" all the plutonium, and even burn a limited amount of minor actinides.

Otherwise, sooner or later, we will have unusable plutonium (bad isotopic composition) on our hands which we will have to end up considering as waste.

 

[Rade]

There is also the possibility of physical transmutation of radioactive waste,--see these links for information:

http://en.wikipedia.org/wiki/Nuclear_transmutation
http://www.nea.fr/html/trw/index.html
http://www.neutron.kth.se/courses/transmutation/Chapter1.pdf
http://arxiv.org/ftp/physics/papers/0401/0401015.pdf

 

[baywax]

The good way to use plutonium is in fast reactors: it is a very good fuel. For the moment, in certain countries (France, UK,...) one is reprocessing the spend fuel and one extracts the plutonium. In others (Sweden, USA,...) one uses the "open cycle", that is, one considers the spend fuel as waste (which is very wasteful of ressources, but economically for the moment still viable).

Now, plutonium has several problems. It is by far the longest-living nuisible actinide, so in the waste, one counts on 100 000 years for it to take on "background" levels. This is not a problem by itself, but it would be better if this time were limited to 10 000 years of course, which is the case of spend fuel of which the plutonium has been removed but still contains the minor actinides (Np, Am, Cm), simply because the migration models have less uncertainties over 10 000 years than over 100 000 years. So one can put smaller error bars on the predictions of the safety of a repository over 10 000 years than over 100 000 years.
Moreover, plutonium is of course military a sensitive material, although this is over-emphasised: the plutonium from thermal power plants is of such an isotopic composition that it is difficult (although not impossible) to use to make a nuclear weapon.

All these are good reasons on the "waste" side to remove the plutonium. On the "fuel" side, as Azael said, plutonium is a "good fuel", but one has to put a caveat here. It is the perfect fuel for a fast reactor. But in a standard PWR, it is problematic. One can partially reuse it in so-called MOX fuel, but the difficulty is that in a thermal spectrum, the "good" plutonium Pu-239 can fission, but also absorb a neutron to form Pu-240, and so on, which absorps neutrons, which is highly active, and which ends up becoming Pu-241 which decays into Am-241, a nuisance.

So as long as we have a park of just PWR or BWR with thermal spectrum, we have only a limited possibility to re-use the plutonium. The plutonium from used MOX fuel is so good as unusable in a thermal (water) reactor, and will end up producing a lot of minor actinides. The gain in "waste" this way is limited, and the gain in fuel also (about 10-20% economy in fuel).

Genuine plutonium recycling only really makes sense if we have in the park of reactors, also a certain fraction of fast reactors. They can "eat" all the plutonium, and even burn a limited amount of minor actinides.

Otherwise, sooner or later, we will have unusable plutonium (bad isotopic composition) on our hands which we will have to end up considering as waste.

Is there some etiquette to disposing of nuclear waste? I mean, dog owners are faced with the disposal task everyday. I don't know if its done well. But its not on the streets or the grass (in most cases). Its in the landfill decomposing. But, someday, someone is going to build on that land fill.

Someday, there could be a host of other things going on like high water, earthquakes where you least expect them, future excavations. What if records are lost and wiped out, and people in 3490 AD are planning a tunnel through what they think is wilderness and they bore right through this land mine of plutonium? There are a thousand scenarios that come to mind where contamination and severe mutation take place because, today, we couldn't figure out a way to neutralize our nuclear waste... or perhaps do without nuclear power.

I mean, at one point we only had wind mills and sails for energy. If we bump into a wreck of one of these it doesn't kill or mutate the whole family. Is there a way to ensure, completely, that all nuclear waste can be disposed of in a benign way?

 

[CaptainQuasar]

I just wanted to say to everyone, good questions baywax and great high-information-density answers.

⚛​

 

[baywax]

I just wanted to say to everyone, good questions baywax and great high-information-density answers.

⚛​

Yes Captain... I forgot to thank all the contributors for the extremely in-depth answers we're getting. After the philosophy section, this is a real treat! My gratitude to you guys and here's me hauling back a big (hopefully non-contaminated) beer in your honour, eh!.

edit: speaking of migration levels, after Chernobyl, there was a map showing the spread of the contaminants. It seemed to cover a large area, well into Eastern Germany and even over some of Ireland as I remember. Is this the spread of the irradiated gases Azael mentioned and not to do with the properties of plutonium or uranium?

 

[baywax]

There is also the possibility of physical transmutation of radioactive waste,--see these links for information:

http://en.wikipedia.org/wiki/Nuclear_transmutation
http://www.nea.fr/html/trw/index.html
http://www.neutron.kth.se/courses/transmutation/Chapter1.pdf
http://arxiv.org/ftp/physics/papers/0401/0401015.pdf

I notice in the wicipedia article the mention that "cesium has a relatively short biological halflife (1 to 4 months) while strontium and radium both have very long biological half-lives"

How is the term "biological" being applied here? Does this describe the halflife of cesium when it is present in an organism?

I've worked around linear-accelerators and CT scanners and MRI units etc... I know Barium is used to image areas of anatomy. Is barium part of the radioactive family with a short biological halflife?

 

[Astronuc]

Barium used for X-ray imaging of the GI tract is not radioactive.

Barium sulphate (BaSO₄) is insoluble and used for body imaging (barium meal).

http://www.webelements.com/webelements/elements/text/Ba/phys.html

Density is ~3.5 g/cm³
http://www.webelements.com/webelements/elements/text/Ba/phys.html

Cs is chemically similar to Na and K, so can be taken up and excreted similar. Sr and Ra are chemically similar to Ca, which of course is important in the structure of bones. Sr and Ra tend to accumulate in the bones where they can do damage to the blood system in addition to underming the skeletal structure (as well as cause sarcomas), and could damage the spinal cord if sufficient radioactive Sr or Ra accumulates in the spine/vertebrae.

 

[vanesch]

Is there some etiquette to disposing of nuclear waste? I mean, dog owners are faced with the disposal task everyday. I don't know if its done well. But its not on the streets or the grass (in most cases). Its in the landfill decomposing. But, someday, someone is going to build on that land fill.

It is DEEP geological disposal: of the order of 200 - 700 meters under the surface of the earth. The current maximum exposure limit during the lifetime of the site in all "reasonable" scenarios is set to 0.3 mSv/year (to give you an idea, the average yearly dose by natural background is 2.4mSv/year). A site is not acceptable if you find a reasonable scenario where there's a higher dose risk than 0.3 mSv/year. However, most scenarios give you rather 10 microsievert (=0.01mSv/year) per year! The "lifetime of the site" is the time it takes for the radiotoxicity to fall back on that of natural uranium ore (which are these famous lifetimes: 300-400 years for fission products, 10 000 years for minor actinides and 100 000 years for plutonium).

Of course, the discussion is "what is a reasonable scenario". Usually one takes that precise records are kept for about 500 years (so no drills etc... during this period). After that, one considers things like a borehole for water and such.
Now, of course, or 1000 years from now we became cavemen, or we're all dead, or we still have nuclear technology which allows us to sample stuff. If we're cavemen, we won't dig holes that deep.

Of course you cannot foresee everything. That's what "reasonable" stands for. People (if they exist) 1000 years from now also have to take up a bit their responsability, like taking samples where they are drilling.

Someday, there could be a host of other things going on like high water, earthquakes where you least expect them, future excavations. What if records are lost and wiped out, and people in 3490 AD are planning a tunnel through what they think is wilderness and they bore right through this land mine of plutonium? There are a thousand scenarios that come to mind where contamination and severe mutation take place because, today, we couldn't figure out a way to neutralize our nuclear waste... or perhaps do without nuclear power.

These "thousands of scenarios" is exactly what people try to find out, and calculate/estimate the doses that result from it.

I mean, at one point we only had wind mills and sails for energy. If we bump into a wreck of one of these it doesn't kill or mutate the whole family. Is there a way to ensure, completely, that all nuclear waste can be disposed of in a benign way?

You rarely bump into a windmill 500 meters underground, do you ?

 

[CaptainQuasar]

Little tidbit: http://downlode.org/Etext/wipp/" from Sandia National Laboratories analyzing how such a repository of waste should be marked.

⚛​

 

[vanesch]

There is also the possibility of physical transmutation of radioactive waste,--see these links for information:

http://en.wikipedia.org/wiki/Nuclear_transmutation
http://www.nea.fr/html/trw/index.html
http://www.neutron.kth.se/courses/transmutation/Chapter1.pdf
http://arxiv.org/ftp/physics/papers/0401/0401015.pdf

Although it is *physically* possible to do this, and although there is a big research interest in this at the moment, I seriously question the industrial utility of it.

Indeed, the ultimate goal is to lower the risk of nuclear waste over the long term. Here, the risk is the expected number of death (number of exposed people x probability that they die of their exposure).

The risk for the repository is pretty small ! It is only in pretty unlikely scenarios that we obtain doses that might even become measurable above the background!
Now, these transmutations also involve a lot of manipulations of the waste, transport to the transmutation centre etc... There is always a minor risk in these manipulations that something goes wrong, and that, say, a worker get exposed or something. So it is far from obvious that these transmutations, everything included, REDUCE the overall risk! They might even increase it seriously (while it would still be very low of course).

In other words, we would put the lives of people at a slightly increased risk NOW, just to avoid very very unlikely risks to hypothetical people 1000 years from now.

 

[russ_watters]

Is there a way to ensure, completely, that all nuclear waste can be disposed of in a benign way? [emphasis added]

The answer to this question is, of course, no. But this is not a flaw in nuclear power, it is a flaw in the general public's understanding of the concept of risk management. That's the reason why some people are terrified of airplanes, while few give driving a second thought even though by all reasonable measures, a car is much more likely to kill you.

Risk management is exactly what the name implies - management (not elimination) of risk. You cannot eliminate risks, you can only reduce them to reasonable levels and choose a course of action that has the most reasonable risk that is balanced against the reward.

Currently, many people are terrified of the pollution risks of nuclear power, but don't give the oil and coal power plant pollution risks much thought (at least insofar as they don't attempt to shut down an entire country's production of them). This is irrational considering the risks of nuclear power in a country like the US are extremely low and the benefit extremely large. At the same time, the [pollution] risks of coal and oil power are much larger.

Risk management means choosing the correct course of action. Nuclear power is the correct course of action.

 

[Azael]

There are a thousand scenarios that come to mind where contamination and severe mutation take place because, today, we couldn't figure out a way to neutralize our nuclear waste... or perhaps do without nuclear power.

The number one protection is simply that the long lived waste products do not spread easily. The are almost insoluble in water and they tend to cling to every surface they get into contact with. Even if all the containers in a waste repository would fail it would still take a very long time for any long lived waste products to reach the surface and then it would be in extremely low concentrations. Its as close to fool proof as anything can come. Even if someone in the future drill straight down into the repository the exposure to radiation will still be very restricted. The swedish repository is even expected to handle a new ice age.

edit: speaking of migration levels, after Chernobyl, there was a map showing the spread of the contaminants. It seemed to cover a large area, well into Eastern Germany and even over some of Ireland as I remember. Is this the spread of the irradiated gases Azael mentioned and not to do with the properties of plutonium or uranium?

It was mostly iodine, cesium ect. I doubt much plutonium was spread far from the reactor, it just doesn't spread easily. Nuclear weapons test has spread much much more plutonium into the atmosphere.

Although it is *physically* possible to do this, and although there is a big research interest in this at the moment, I seriously question the industrial utility of it.

Indeed, the ultimate goal is to lower the risk of nuclear waste over the long term. Here, the risk is the expected number of death (number of exposed people x probability that they die of their exposure).

The risk for the repository is pretty small ! It is only in pretty unlikely scenarios that we obtain doses that might even become measurable above the background!
Now, these transmutations also involve a lot of manipulations of the waste, transport to the transmutation centre etc... There is always a minor risk in these manipulations that something goes wrong, and that, say, a worker get exposed or something. So it is far from obvious that these transmutations, everything included, REDUCE the overall risk! They might even increase it seriously (while it would still be very low of course).

In other words, we would put the lives of people at a slightly increased risk NOW, just to avoid very very unlikely risks to hypothetical people 1000 years from now.

IMO the main advantage of getting rid of long lived waste by transmutation is the PR side, then the nuclear industry can say that the waste problem has a solution and its not a problem anymore. The environmental organisations have already made the public sceptical towards geological storage. With carbon taxes that option will hopefully be economicaly competitive.

Seems like most fast reactor projects in the pipeline have the goal to be able to accept fuel with a mixture of Pu and minor actinides like that LWR's produce and that solves that problem without exotic concepts like ADS. But even the economics of ADS might become fairly reasonable. Atleast if it turns out as optimistic as the researchers working on it hopes.
http://www.neutron.kth.se/publications/library/DanielMSc.pdf

Moreover, plutonium is of course military a sensitive material, although this is over-emphasised: the plutonium from thermal power plants is of such an isotopic composition that it is difficult (although not impossible) to use to make a nuclear weapon.

One argument that sometimes pop up in sweden is that after some time(tens of thousands of years) has passed most of the plutonium in the repository will be Pu-239 since the other isotopes have shorter half lives. So it could become a "plutonium mine" for future generations. I have a hard time taking that argument seriously since the current generation can not be expected to prevent the conscious descisions of future generations, but arguments like that has to be countered for nuclear to gain trust again. Just another reason to destroy it for good.

The best plan any country has so far is by far India. They plan on three stages.

Stage one, use heavy water moderated reactors running on natural uranium.

stage two, burn the plutonium and minor actinides produced in stage one in fast breeder reactors that breed u-233 from thorium instead of plutonium from u-239.

Stage three, use the u-233 in breeders running on pure thorium fuel cycles.

Stage two takes care of all long lived waste and stage three no longer produce any significant ammounts of long lived waste.

A thorium(u-233 breeder fuel cycle, especialy with molten salt reactors, looks very good next to a Pu breeder fuel cycle if looking at it from a global perspective with the HUGE ammounts of Pu that would be in circulation if nuclear power is to play a significant part of energy production.

 

[vanesch]

IMO the main advantage of getting rid of long lived waste by transmutation is the PR side, then the nuclear industry can say that the waste problem has a solution and its not a problem anymore.

I think it is an extremely dangerous PR game, because there are many chances that the COMPLETE burnup of all actinides will prove industrially impossible or economically a disaster. Maybe not, but there are serious chances that it will be.

As such, then the argument is perfect: "they finally admitted that they didn't know what to do with the waste, they promised they could burn it, and now it is clear that they can't".

 

[baywax]

The answer to this question is, of course, no. But this is not a flaw in nuclear power, it is a flaw in the general public's understanding of the concept of risk management. That's the reason why some people are terrified of airplanes, while few give driving a second thought even though by all reasonable measures, a car is much more likely to kill you.

Risk management is exactly what the name implies - management (not elimination) of risk. You cannot eliminate risks, you can only reduce them to reasonable levels and choose a course of action that has the most reasonable risk that is balanced against the reward.

Currently, many people are terrified of the pollution risks of nuclear power, but don't give the oil and coal power plant pollution risks much thought (at least insofar as they don't attempt to shut down an entire country's production of them). This is irrational considering the risks of nuclear power in a country like the US are extremely low and the benefit extremely large. At the same time, the [pollution] risks of coal and oil power are much larger.

Risk management means choosing the correct course of action. Nuclear power is the correct course of action.

I see your point here russ. Its like how its more likely that I will crash on the highway, in terms of odds, than if I am flying to my destination.

You're right of course. Its all in the management of these resources and I would think that by now we are getting better at educating our technicians in proper management of nuclear energy. It seems that this education hasn't really taken place as well in the coal and gas industries or it may be that profit has taken precedent over public/environmental health and safety. But, what assurance is there that the same won't happen with the nuclear program. Can it be completely regulated by the Feds or is it on the free market chopping block like health care?

 

[baywax]

The number one protection is simply that the long lived waste products do not spread easily. The are almost insoluble in water and they tend to cling to every surface they get into contact with. Even if all the containers in a waste repository would fail it would still take a very long time for any long lived waste products to reach the surface and then it would be in extremely low concentrations. Its as close to fool proof as anything can come. Even if someone in the future drill straight down into the repository the exposure to radiation will still be very restricted. The swedish repository is even expected to handle a new ice age.



It was mostly iodine, cesium ect. I doubt much plutonium was spread far from the reactor, it just doesn't spread easily. Nuclear weapons test has spread much much more plutonium into the atmosphere.



IMO the main advantage of getting rid of long lived waste by transmutation is the PR side, then the nuclear industry can say that the waste problem has a solution and its not a problem anymore. The environmental organisations have already made the public sceptical towards geological storage. With carbon taxes that option will hopefully be economicaly competitive.

Seems like most fast reactor projects in the pipeline have the goal to be able to accept fuel with a mixture of Pu and minor actinides like that LWR's produce and that solves that problem without exotic concepts like ADS. But even the economics of ADS might become fairly reasonable. Atleast if it turns out as optimistic as the researchers working on it hopes.
http://www.neutron.kth.se/publications/library/DanielMSc.pdf



One argument that sometimes pop up in sweden is that after some time(tens of thousands of years) has passed most of the plutonium in the repository will be Pu-239 since the other isotopes have shorter half lives. So it could become a "plutonium mine" for future generations. I have a hard time taking that argument seriously since the current generation can not be expected to prevent the conscious descisions of future generations, but arguments like that has to be countered for nuclear to gain trust again. Just another reason to destroy it for good.

The best plan any country has so far is by far India. They plan on three stages.

Stage one, use heavy water moderated reactors running on natural uranium.

stage two, burn the plutonium and minor actinides produced in stage one in fast breeder reactors that breed u-233 from thorium instead of plutonium from u-239.

Stage three, use the u-233 in breeders running on pure thorium fuel cycles.

Stage two takes care of all long lived waste and stage three no longer produce any significant ammounts of long lived waste.

A thorium(u-233 breeder fuel cycle, especialy with molten salt reactors, looks very good next to a Pu breeder fuel cycle if looking at it from a global perspective with the HUGE ammounts of Pu that would be in circulation if nuclear power is to play a significant part of energy production.

Thanks Azael. The migration factor was something I had no idea about. What springs to mind every time are these 3 mile Island and Chernobyl scenarios. Its particularly enlightening to know that a lot of nuclear material will not contaminate water.

I worked for an environmental protection company that monitors diamond mines, gold mines and aluminum producers. One time there was a creek near a mine for nickel and components of aluminum. Before the mine went in we sampled the creek for levels of minerals etc... and found it to contain unacceptable levels of aluminum... before any mining took place! It was a naturally occurring level.

Does uranium or plutonium or radium pose a risk in its natural state, say if you camp on top of it over night?

 

[Astronuc]

Does uranium or plutonium or radium pose a risk in its natural state, say if you camp on top of it over night?

Plutonium has such a relatively short half-life in terms of the age of the earth, that one does not find it readily in the environment. Uranium is naturally occurring in granite and certain areas, as it thorium. Radium is a daughter product in the decay chains of U and Th, and is present in trace quantities.

http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radser.html

Camping overnight on top of a geological (natural) deposit of U (with trace of Pu) is not harmful.

When using Ra-226/228 in a lab, it is shielded as are all radionuclides. It is a matter of using the appropriate shielding and procedures when dealing with radioactive material.

 

[vanesch]

Thanks Azael. The migration factor was something I had no idea about. What springs to mind every time are these 3 mile Island and Chernobyl scenarios.

This has been discussed already in a few threads, but you have to know that at Three Miles Island, nothing seriously happened externally, and that there was still a very long way for 3 Miles Island to turn into something that even remotely would resemble Chernobyl.

At 3-miles island, what happened was that the operators got into panic mode on a minor error, took about every wrong decision that they could for about 6 hours, emptied by error part of the (shut-down) reactor vessel from its cooling water, and hence, part of the fuel which was still producing decay heat, melted, until people got wiser, started pumping in water again, and cooled down the whole business again. In the whole operation, nor the reactor vessel, nor the containment building has at any moment been put in danger. So containment of most of the radioactivity was, at any moment, secure. The only radioactivity that was released was on purpose: the steam that was produced when people pumped in water again. They evaluated the potential risk, decided that it was below the specified norms, and proceeded. NOBODY got a dose over the legally specified maximum dose in this "terrible accident".

So 3-miles island proved that you could do the most stupid things with a reactor for about 6 hours, and that still nobody got hurt (but that you damaged the installation). Try that with a car :tongue: In other words, 3-miles island proved in fact the enormous SAFETY of the design of a western nuclear power plant. And things got much much better since then.

Chernobyl is the opposite. Chernobyl is the illustration that if you REALLY want to cause a disaster in nuclear technology, you have to start with a BAD DESIGN, and not provide any build-in safety. Next, you need to have totally incompetent, reckless idiots steering the plant and ask them to do a stupid experiment. And even if you do that, it will take you some time before things go wrong, because although Chernobyl went wrong, ONE HAD ALREADY DONE a similar experiment elsewhere, but it didn't go (too) wrong. And then you need clueless officials who don't do anything sensible for the first 36 hours after the accident.

The Chernobyl reactor was a bad design (and that was WELL-KNOWN), in that the reactor was inherently instable, and didn't have any passive shut-down mechanism (as has every western reactor). It didn't have any automatic security system either, that shuts down the reactor when operation parameters get in the red. It wasn't build in a pressure vessel, and it wasn't build in a containment building: the building had WINDOWS.
There were no safeguards on stupid operator commands, such as pulling out the control rods beyond their limit.

One single of these measures would have been sufficient to avoid the accident.

So what happened in short is that the operators of the night crew, who didn't have any experience with a nuke (they were used to a coal plant), wanted to do the experiment, made an error which made the reactor almost shut down. Because they wanted to avoid by all means that it stopped (as this would prevent them doing the experiment, and probably get their ears washed in the morning), they did a series of incredibly dangerous things (such as pulling out all safety bars beyond their limits, pumping in too much water etc...). Because of the unstable and unsafe design, the reactor finally did what they wanted, namely diverge again, but as there was no build-in stop to the power, it climbed to several tens of times its nominal power in a few seconds and hence got incredibly hot in a very short time.
Because there was no pressure vessel, the thing underwent a steam explosion, and because there was no containment building, well, it blew essentially up in the open.
Because there was no passive safety, the reactor didn't shut down! It continued to produce heat, and hence the graphite caught fire. So we had a WORKING reactor, producing heat, in the mid of a coal fire, in the open, full of radioactive elements (fission products, and military stuff to be irradiated), which rose of course in the convection of hot air.

So what did they do ? They called the fire brigade, and didn't tell them it was the reactor that was on fire!
It was only THE NEXT DAY that one realized what happened, and that boron was dropped (with helicopters) on the reactor to STOP it from working.
Only 36 hours after the explosion, one started to evacuate the nearby town.

Now, in as much as this was a true disaster, the world didn't disappear. It was of the same order of magnitude as other disasters that humanity sometimes faces.

The whole course of events, from the start to the end, is totally unthinkable in a western power plant. It is what you get when there is incompetence and recklessness on all levels, from the design, to the operation, to the crisis management.

 

[Azael]

I think it is an extremely dangerous PR game, because there are many chances that the COMPLETE burnup of all actinides will prove industrially impossible or economically a disaster. Maybe not, but there are serious chances that it will be.

As such, then the argument is perfect: "they finally admitted that they didn't know what to do with the waste, they promised they could burn it, and now it is clear that they can't".

Hmm yeah I se your point, offcourse there will never be 100% burnup of all actinides. But if they can be reduced to a level that the need for a 100 000 years repository is eliminated its enough. I guess some amount of actinides can be burried with the fissions products and still not be a threat after the 500-1000 years that is needed for fp's to decay? Aslong as the waste after 1000 years have a activity close to the activity of uranium ore. A repository will be needed for the fp's regardless.

But id say that if we can not get atleast 99% burnup of the minor actinides we should drop the uranium fuel cycle completely and follow the same plan as India, a future with several thousand reactors all producing waste at the same ammounts/kWh as todays is unacceptable in the long term.

 

[vanesch]

But id say that if we can not get atleast 99% burnup of the minor actinides we should drop the uranium fuel cycle completely and follow the same plan as India, a future with several thousand reactors all producing waste at the same ammounts/kWh as todays is unacceptable in the long term.

Sure, the idea is to switch to fast breeders, no ? The current cycle is not only producing annoying waste, it is especially wasteful with ressources!

 

[baywax]

Sure, the idea is to switch to fast breeders, no ? The current cycle is not only producing annoying waste, it is especially wasteful with ressources!

This may not be completely related to the thread but, why isn't there more research into the Hydrogen Fuel Cell generators (like the ones being used for individual households in Japan)? This would certainly reduce the waste of resources and the waste disposal issue.
They were using the Fuel Cell on the Apollo missions (40+ years ago), there must have been some advancements with them by now.