Would our nuclear scientists care to comment?

[Phanerothyme]

Interesting story from El Reg here: http://www.theregister.co.uk/2013/03/14/nuclear_reactor_salt/

 

A company spun off from MIT is claiming it has cracked the holy grail of nuclear technology: a reactor design that runs on materials the industry currently discards as waste and which could meet all of the world's power demands for the next 70 years. It's also "walk-away safe," the designers claim, making it immune to the kind of meltdown that destroyed the Fukushima reactors.

 

What say ye?

[Mecky]

Can they make extortionate profit out of such a scheme? If not I can't see it happening.

[Vague_Boy]

What say ye?

 

Certainly sounds interesting, hopefully it will pan out.

 

We've had claims like this in the past that proved to be flawed, remember the cold fusion discovery in the 1980s?

 

Can they make extortionate profit out of such a scheme? If not I can't see it happening.

 

Profit, oh the horror.

 

Doubtless you eat in the popular, not-for-profit MacDonalds restaurants, watch the not-for-profit Sky TV and buy your food from not-for-profit stores like Tesco or Asda.

[Mecky]

Certainly sounds interesting, hopefully it will pan out.

 

We've had claims like this in the past that proved to be flawed, remember the cold fusion discovery in the 1980s?

 

 

 

Profit, oh the horror.

 

Doubtless you eat in the popular, not-for-profit MacDonalds restaurants, watch the not-for-profit Sky TV and buy your food from not-for-profit stores like Tesco or Asda.

 

Well duuuhhh

[Obelix]

Interesting story from El Reg here: http://www.theregister.co.uk/2013/03/14/nuclear_reactor_salt/

 

 

 

What say ye?

 

Molten salt reactors have been around for a long time, as have the complete actinide burning series. The UK has done a considerable amount of research on breeder systems such as the FBR at Dounreay.

 

There are some technical considerations, such as the reprocessing systems which by their nature have to be remotely operable - whilst you can build a reactor that "burns" everything it's far better to have a couple optimised for different systems. Generally speaking you would have a normal thermal reactor like our current BWR/PWR ones, and the waste from this would be burnt in a molten salt reactor that also breeds more fissile U-235 from U-238.

 

Advantages

They can run hot enough to generate hydrogen directly, enabling a true hydrogen transport system.

Online reprocessing means that they can be free from the xenon trap, so they can react to load changes within a minute or so, making them viable as a peaking plant as well as a baselaod plant.

They have a large negative void coefficiency, so are self limiting in case of a problem. You can also dump the core into a large plate if you really need to stop it. Or you can flood the system with balls of boron to stop it, and recover these later with no real damage to the reactor

You can burn the entire actinide series with a properly designed system meaning that you can use in theory all of the uranium you mine, instead of about 0.4% of it as at present.

It generates a small amount of exceedingly high level waste that needs care for only a few decades, rather than a few milennia. Waste disposal is far easier and can be managed onsite, cleanup being far easier.

 

Disadvantages

They can make an enourmous amount of plutonium easily and contribute to proliferation concerns.

Making the reactor vessel is tricky - about the only feasible alloy is Hastelloy and even that will be attacked if you are not careful. It also has a short-ish life so you have to replace critical components more frequently than in a normal reactor (normal reactors also use Hastelloy but at a lower primary loop temperature)

It's never been tried full scale before - there are a few small pilot plants, the ARE, and the MSRE but no-ones built a full size plant. There would have to be an intermediate plant first, before a fullsize gigawatt class station was considered.

 

---------- Post added 18-03-2013 at 10:31 ----------

 

Certainly sounds interesting, hopefully it will pan out.

 

We've had claims like this in the past that proved to be flawed, remember the cold fusion discovery in the 1980s?

 

Unlike cold fusion, this one has actually been proven on a small scale, the Aircraft Research Establishment and the molten salt research experiment reactors were both this type of reactor.

 

Profit, oh the horror.

 

Doubtless you eat in the popular, not-for-profit MacDonalds restaurants, watch the not-for-profit Sky TV and buy your food from not-for-profit stores like Tesco or Asda.

 

You have to understand Mecky doesn't necessarily understand - he just hits on keywords and reacts like Pavlov's dogs.

[mickey finn]

Molten salt reactors have been around for a long time, as have the complete actinide burning series. The UK has done a considerable amount of research on breeder systems such as the FBR at Dounreay.

 

There are some technical considerations, such as the reprocessing systems which by their nature have to be remotely operable - whilst you can build a reactor that "burns" everything it's far better to have a couple optimised for different systems. Generally speaking you would have a normal thermal reactor like our current BWR/PWR ones, and the waste from this would be burnt in a molten salt reactor that also breeds more fissile U-235 from U-238.

 

Advantages

They can run hot enough to generate hydrogen directly, enabling a true hydrogen transport system.

Online reprocessing means that they can be free from the xenon trap, so they can react to load changes within a minute or so, making them viable as a peaking plant as well as a baselaod plant.

They have a large negative void coefficiency, so are self limiting in case of a problem. You can also dump the core into a large plate if you really need to stop it. Or you can flood the system with balls of boron to stop it, and recover these later with no real damage to the reactor

You can burn the entire actinide series with a properly designed system meaning that you can use in theory all of the uranium you mine, instead of about 0.4% of it as at present.

It generates a small amount of exceedingly high level waste that needs care for only a few decades, rather than a few milennia. Waste disposal is far easier and can be managed onsite, cleanup being far easier.

 

Disadvantages

They can make an enourmous amount of plutonium easily and contribute to proliferation concerns.

Making the reactor vessel is tricky - about the only feasible alloy is Hastelloy and even that will be attacked if you are not careful. It also has a short-ish life so you have to replace critical components more frequently than in a normal reactor (normal reactors also use Hastelloy but at a lower primary loop temperature)

It's never been tried full scale before - there are a few small pilot plants, the ARE, and the MSRE but no-ones built a full size plant. There would have to be an intermediate plant first, before a fullsize gigawatt class station was considered.

 

---------- Post added 18-03-2013 at 10:31 ----------

 

 

Unlike cold fusion, this one has actually been proven on a small scale, the Aircraft Research Establishment and the molten salt research experiment reactors were both this type of reactor.

 

 

 

You have to understand Mecky doesn't necessarily understand - he just hits on keywords and reacts like Pavlov's dogs.

 

Just like you did with that infant like end bit, you were doing fine up until then

[Phanerothyme]

Molten salt reactors have been around for a long time, as have the complete actinide burning series.…

.

 

 

Thanks Obelix, I knew I could count on the forum for some solid background - El Reg likes to think it knows it all, but rarely does.

[Cyclone]

Interesting story from El Reg here: http://www.theregister.co.uk/2013/03/14/nuclear_reactor_salt/

 

 

 

What say ye?

 

I read the comments on that story a few days ago. There are some very detailed technical analysis from people who seem to know what they are talking about. The summary of which is that this is interesting, but the paper that's been written has ignored several key technical issues that have to be solved for this to be practical.

 

The main one of those issues IIRC was the removal of the high level waste product from the molten solution, it sounds like it's a rather tricky step, and key to the process or the reaction is poisoned and fails (due to high neutron absorption I think).

[Dromedary]

Quote from article;

 

"A company spun off from MIT is claiming it has cracked the holy grail of nuclear technology;"

 

So as of now its just a claim so not very exciting.

[Obelix]

I read the comments on that story a few days ago. There are some very detailed technical analysis from people who seem to know what they are talking about. The summary of which is that this is interesting, but the paper that's been written has ignored several key technical issues that have to be solved for this to be practical.

 

The main one of those issues IIRC was the removal of the high level waste product from the molten solution, it sounds like it's a rather tricky step, and key to the process or the reaction is poisoned and fails (due to high neutron absorption I think).

 

One of the by products from a fission reactor is Xenon - this is a powerful neutron poison as it has a truly enourmous cross section for capturing neutrons. What happens is that iodine 135 is formed which then turns into xenon 135.

 

Normally this isn't a problem - the poisioning effect of xenon is counteracted by having a well, a reactive reactor that can produce enough neutrons to overcome it. However if you shut it down you have a problem restarting because the neutron flux is very low and it cannot overcome the xenon unless you pull all the control rods out. The last time someone did this was at Chernobyl.... although the RBMK reactor had a really poor design, and no containment, the problem was the reactor operators doing something really stupid because they were scared of their boss, but I digress....

 

Once shut down you have to let the iodine, and then the xenon decay away - this is unfortunate as it takes about three days to do so, so you cannot run a nuclear plant during the week and switch it off at the weekend. If you could remove the iodine as it's formed however that would be good, as you could then have a large step change in plant output power.

 

So... in a molten salt system you either..

 

a) pump the fuel though a small core and react it there and then have the fuel go through a (very) large loop where it's out of the core for a day or so. This lets the iodine and xenon decay to a manageable level. To reduce power you pump the fuel through the core more slowly let it get more poisioned and less reactive. If you need to increase power pump faster and get "fresh" fuel.

 

b) boil off the iodine as it's formed and let it decay in a headspace above the rector. This is a better bet as you dont need a pump for the fuel system - pumping a molted fluoride salt at 700C is not most peoples idea of an easily acheivable engineering practice....

 

Now that is actually easy to do. Trickier is to remove the unwanted waste products that are heavier actinide elements, the transuranics. You can process these out using PUREX or a similar system but you have to do it remotely, using equiment that is capable of sustaining high levels of neutron and gamma radiation. That means hardened electronics, exotic alloys that don't go excessivly brittle (Wigner energy which is found in neutron embrittled graphite was the cause of the Windscale fire for example).

 

It's far easier to just react the transuranics away and burn them as well. If you can do that, you can just also tip in all the waste that the world has and burn that too and make more power - that's what this setup is designed to do. You still have to process some very reactive waste out of the far end but the final product is tiny compared to what we have to deal with today, and perversely because it's very radioactive it's easy to deal with in storage because it decays quickly so it's safe to deal with after a few decades, rather than a few millenia like our current waste

 

---------- Post added 19-03-2013 at 12:21 ----------

 

Just like you did with that infant like end bit, you were doing fine up until then

 

I'm sorry you find reality upsetting. If you don;t have anything useful to contribute then perhaps you could join Mecky?