Page 3 of 3

Re: Wendelstein 7-X has successfully finished its second major experimental run

Posted: Thu Jan 10, 2019 3:53 am
by Richard Hull
The fission plant explosions are all hydrogen explosions or steam explosions and not fission explosions. Most all accidents thus far have either run a high probability of hydrogen explosion or have actually had a hydrogen explosion, thus, blown up in actuality.

I feel or rather felt that every one knew that.

Richard Hull

Re: Wendelstein 7-X has successfully finished its second major experimental run

Posted: Thu Jan 10, 2019 11:56 am
by Dennis P Brown
American level enriched fission reactors can't create a nuclear explosion as pointed out. Yes, as Richard said, hydrogen gas has been the issue in any such explosions - in a runaway situation the hot fuel breaks water into hydrogen and oxygen gas. A mixture not friendly to ignition sources - and also under a lot of pressure making it more unstable still.

That all said, breeders can support a nuclear explosion due to the plutonium fuel elements (in rods) used for the breeding process. Hence, melting (for any reason) can lead to a real danger of a nuclear explosion. Hence, these are not reactors to be taken lightly. That said, any nuclear run away and fuel melt down in a breeder will not in any manner, shape or form be like any atomic bomb explosion - it does not have even remotely that level of weapons grade fuel density.The building will be breached in a big way and the reactor core turned into a large pile of shrapnel thrown many hundreds of meters and certainly a large vapor cloud of very fun radioactive waste burning away until stopped by desperate means (air drop comes to mind.) Not a situation anyone would want to be downwind for a very long way and a few thousand years there after.

As for thorium breeders, a bit different fuel system (enriched uranium rods are added) but I have no real knowledge if they offer similar issues. I do not believe they do.

There is one reactor that is essentially fool proof in a safety sense (of course, we know what that implies and that is the Candu reactor. It uses heavy water so is costly in that respect. It can't really melt down so that failure path isn't a concern (unless one pumps out the water) and since it uses un-enriched uranium has a far cheaper fuel that again, is safer to install and posses no weapons risk to make or install (at first; in time it produces a lot of plutonium (more slowly than a US plant) so that becomes an issue with time.) It is less efficient than any American plant and produces as much waste (per kilowatt generated) as any plant.

So, while a lot cheaper to build and requiring fewer operating personnel, the heavy water cost is not cheap so the net cost to build was similar in the late 60's as American plants then. I guess compared to modern plants, it would be a lot cheaper to build due to not needing new fancy design safety systems nor suffer massive design changes during construction like current American plants (why? That drives me crazy to understand and I gave up trying) but that is complete speculation on a Candu current cost, and hardly science.

Finally, even best case fusion (and that assumes all goes well for the stellarator), twenty years to get a net power, ignition reactor (used ONLY as a test bed) would really require everything to flow perfectly. As for a power plant level, that is far, far more difficult and in that, Richard isn't too far off at all. So, while I'll say that a test bed fusion reactor will occur within our children's lifetime, that time frame isn't anywhere as likely for a real power plant - certainly not unless a major need is found. The engineering issues for a commercial fusion power plant are massive - i.e. the extreme neutron and gamma ray production of a deuterium/tritium fuel burn in a plasma makes a fission reactor environment look somewhat tame. I'll add that super conducting magnets have little long term tolerance to any significant neutron flux and do remember that magnet field strength is a one over "R" squared issue so thick absorbents aren't easy to deal with in that design situation. Also, first walls won't last very long, either and become fiercely radioactive, as well. Gotta love those neutron effects.

Re: Wendelstein 7-X has successfully finished its second major experimental run

Posted: Thu Jan 10, 2019 3:07 pm
by Ameen Aydan
I had the opportunity to see one of the Canadian made CANDU reactors a long time ago here in Ontario. Now looking on the internet, I can find that this design is in fact a very desirable one. The only problem with this reactor is as you mentioned, the cost. They sold a couple reactors at first and later got f*cked over because of the prices. No one bought the design and the company failed to keep the design in the market, eventually forcing them to cancel the design and move to a different one. The ACR (Advanced CANDU Reactor) was another design they tried to sell. No buyer, the company cancels.

In all of these situations the cost always forced very good designs to be retired. Now here's a slice of my cake.

I think that though the over whelming costs is not a good factor to consider in this reactor it will always become cheaper. It is the most basic knowledge of a business. People will always find ways to make things cheaper and more accessible to sell better. A good example is Tesla's batteries. They used to be relatively expensive to manufacture which is why lots of people turned away from it in the beginning. But now with ever increasing efficiency in production, they managed t bring the price, A LOT. I don't have any number but it's easy to find.

So where does this connect? Well, this always turns out to be the outcome in this certain aspect of capitalism. If the heavy water was really that expensive and people really want the CANDU reactor, then people would find ways to make better production methods. Ones that are cheaper and easier. Or, the production method in hand is enhanced to satisfy this equation.

People can always find a way to do what they really want. But the only barrier here is if they WILL do it. That, that is the problem we have.

Ameen Aydan

Re: Wendelstein 7-X has successfully finished its second major experimental run

Posted: Thu Jan 10, 2019 5:45 pm
by Dennis P Brown
Check out how heavy water is made. Thermodynamics is cruel but CANNOT be overcome by any means - if someone finds a way, besides a Noble they'll do away with quantum mechanics, all known chemistry and create a universe based on magic - lol.

More to the point, there is no cost effective way to create heavy water but frankly, that is the only real issue with Candu reactors. Unlike most reactors, they are innately safe so can be built close to where they are needed (assuming sufficient water cooling is available) and don't require expensive fuel. While this ignores waste processing and storage - those two problems certainly DO lend themselves to mass production cost reductions - these are great advantages compared to other nuclear reactor designs.

That said, efficiency is an issue as is the requirement for natural uranium. But those can be dealt with - in the case of fuel, the ocean has more than enough and is cost effective to extract (currently, a factor of eight more expensive than ore but that would come down by economics of scale. Also, enrichment is a very expensive process. Don'y have the figures but I bet sea water derived uranium for a Candu would cost less compared to land based ore that is enriched and used in normal reactors.)

As for efficiency, one accepts what it has but compares the cost to carbon and its real social cost relative to AGW. Since fission is our only low carbon power source that provides giga-watts of power in most places where it is needed - neither solar nor wind can make that claim - and the Candu uses uranium safely, this is our best hope for a low carbon future over the next thirty years. These can be built now.

Re: Wendelstein 7-X has successfully finished its second major experimental run

Posted: Thu Jan 10, 2019 11:25 pm
by Peter Schmelcher
Hydrogen isotopes can now be separated from regular hydrogen using a membrane. I can’t remember the original research article read sometime in the last two years but it was a notable American university. I was amazed that a Nano technology membrane could exploit the very subtle atomic differences. ... ework.html
Another research article I read in the last two years was a new material for reactors that improves with neutron exposure, again it was a notable American university (unfortunately I don’t remember the title so I can’t find any equivalent link).

Re: Wendelstein 7-X has successfully finished its second major experimental run

Posted: Fri Jan 11, 2019 2:33 am
by Rich Feldman
Re. separation of isotopes. It'd be nice to see the numbers for heavy water next to those for uranium enrichment

They might represent two extremes of difficulty, among industrialized separation processes. In between are isotope products with special boron, nitrogen, oxygen, silicon, etc.

Dennis's point about thermodynamics is valid.
There is a theoretical minimum amount of work to make one gram (or one mole) of enriched uranium from the natural element.
And corresponding minimum to make a gram or a mole of heavy water from natural water.
How do the bottom lines compare, for D2O in a CANDU reactor (one time cost?) vs EU in a light water reactor?

Favoring heavy water: mass ratio of isotopes to be separated is 2:1 instead of 235:238.
Favoring uranium: desired isotope enrichment ratio is from 0.7% to 5%, instead of 0.03% to 99.some %.

Vemork Hydro plant in 1935 had heavy water production capacity of 12 tons per year.
220px-Deuterium_oxide_Norsk.jpg (6.95 KiB) Viewed 9680 times

Re: Wendelstein 7-X has successfully finished its second major experimental run

Posted: Fri Jan 11, 2019 3:49 am
by Ameen Aydan
I think you guys interpreted what I said incorrectly. But I did give a bad explanation.

I wasn't trying to say that there will be new technologies. I have seen how uranium is enriched and how D2O is made. They are both a very hard process. Rather than coming up with new technologies, we just make the ones we already have better. Now that might not be the case with D2O, it is possible that we have reached the best possible production method. In that case, people will find ways to cut costs as production becomes more wide spread.

I once again, revisit the same example. Lithium batteries used to be pretty expensive and hard to find... 5 years ago. Now today, there are eBay seller essentially giving them away. Why? Not because we made any improvements to production method. Certainly not because we made new inventions that cut down costs. Rather, it's because the production became more wide spread and now the cheaper person will win.

So from this we see that in some instances, another amelioration was not actually needed, just a little competition.

I would also life to as you guys to please not mind if I made any mistakes here. I'm sourcing this from my mind... not so reliable.

Ameen Aydan

Re: Wendelstein 7-X has successfully finished its second major experimental run

Posted: Fri Jan 11, 2019 12:36 pm
by Dennis P Brown
In the article on deuterium enrichment via membranes, the process has to occur at liquid nitrogen temperatures (not exactly conducive for water to be directly processed - lol.) The process they describe takes a mixture of gases of hydrogen (H2)and deuterium (D2)and separates these. There are no sources for deuterium gas other than first removing the oxygen from water (very energy intensive.) This creates a mixture of the two gas phase - hydrogen and deuterium; then these must be cooled to -173 C using liquid nitrogen (again, rather energy intensive;) finally, pass this mixture through a membrane (some energy cost)- this results in a single increase of D2 to H2 by a factor of 12 (i.e. from 0.03% to 0.36%.)

They give no indication of how many times the process has to be done to get the 99.7% purity required for a heavy water reactor but it is not a linear process with increased number of passes (exchanges never are) - yields will not continue at that high of a value. So, does this process reduce the total energy required to create the deuterium for a reactor? Maybe but if it does, certainly not by much but until they try higher levels of enrichment, even that is a big question.

Ameen, again, no issue with mistakes - unlike you, I don't speak nor can I write in another language so you need offer no apologies! The issue is that mass production of a small, very singular part (i.e. a battery) isn't like making a vast and complex nuclear power plant. No amount of mass production can create a cost curve like a battery or even a car. That said, yes, deciding to build a thousand Candu type reactors over thirty years would bring down the average cost - but not by orders of magnitude (like a battery) and not even an order of magnitude. Labor costs can be reduced only so much, as can materials (Concrete and steel are as cheap as one can already make them and these are the bulk of the materials needed), land (fixed) and a vast infrastructure creation (fuel supply chain - fixed) all have innate costs that do not lend themselves to significant reductions by mass production or clever short cuts.

Really, the question isn't the cost of a fission reactor (either type) - frankly, that is a red herring. The issue is the total cost of carbon; if the long term effects and cost to society are included due to AGW (ignoring issues of coal ash storage (a serious problem), a fission reactor likely is very cost competitive to even a coal plant. The issue is one of absolute safety (this allows a plant closer to a city which saves a great deal of money in reduced power lines - a not insignificant cost factor - and improves overall net efficiency of the final electricity delivered by reducing transmission losses) and the Candu wins that hands down.