Fission news(I know blasphemy )

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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Re: Fission news(I know blasphemy )

Postby KitemanSA » Fri Mar 03, 2017 5:22 am

I'm still not sure where you foresee all the difficulty. Solid salt is brittle. That which hasn't made it to the dump tanks can be easily broken into small pieces and swept up. Then the remainder can be washed up. Clean-up... easy.

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Re: Fission news(I know blasphemy )

Postby RERT » Fri Mar 03, 2017 8:25 am

The Thorcon FDT is below the 'can', which contains the reaction vessel and primary cooling circuit. The facility includes a 400 ton hoist to remove and replace the can as a unit. Once the can is removed, there is no obvious reason why the exposed FDT could not also be lifted out and reprocessed at a specialised facility after a drain event.

That is speculation though: their website is silent on the process after a drain event. I've asked them for more info, we'll see if they care to respond to Joe Public.

D Tibbets
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Re: Fission news(I know blasphemy )

Postby D Tibbets » Sun Mar 05, 2017 8:29 am

Having a removable tank would help cleanup on site( probably by a large amount .But if it weighs 400 tons, it could not be transported intact, except perhaps by barge. Also, clean up of the actual radioactive slug is not just fragmentation of the sludge and sweeping. It is doing so by robotics. Everything will become dangerously radioactive and have to be stored for many years in a safe manner. Any washing fluid would also need to be stored, it could not be released into the environment. Washing may actually increase the radioactive waste volume and weight that has to be handled.

Actual damage to the reactor itself with it's associated steam generating and primary cooling plumbing may not be much with a liquid salt reactor coolent failure. Restoring the reactor function may not be to difficult once the failure points(s) have been corrected. So the plant may be recovered, but the clean up/ removal/ storage of the drain tank and associated plumbing is no trivial endeavor, though I can appreciate designing things so that an intact drain tank can be removed would help the local situation. The tank might be drained if the salt/ sludge is still hot enough to be liquid, or if it is reheated. This would allow transfer to more transportable tanks like railroad tankers similar to those designed for conventional transfer of liquid radioactive wastes to long term storage sites like Yuma Mountain, or processing sites where the products might be processed for subsequent use. Both of these considerations are very expensive though and have suffered considerable public resistance. To establish / reestablish a processing site like what was done for plutonium production would cost tens of billions $ if not hundreds.

This has to be considered in any system that uses fission fuel on industrial scales. My guess is that this is why storage is used for fission waste, it is cheaper than reprocessing and consolidating or reuse of the fission products. The exception is the weapons programs where the cost is acceptable to the parties involved. It has to compete with coal and natural gas. With political green considerations (which are very volatile at this time) nuclear fission gains and perhaps fission reprocessing gains. It also has to compete with wind and solar and other renewables, which is becoming cheaper.

Very large fusion reactors like large tokamaks suffer similar challenges except that the radioactive concerns are several orders of magnitude less problematic (provided there is not an uncontrolled quenching of the superconducting magnets). Concerns are not absent, especially with D-T dependent fusion, but it is better. Fusion advantages increase with D-D or D-D half catalyzed fusion reactors, and of course reach the apex of desirability with aneutronic P- 11B fusion. If liquid salt reactors can be scaled down economically, a failure would result in smaller drain tank size considerations and other advantages that would perhaps reduce the relative costs of recovering or retiring the reactor. The steam generation costs is very significant when considering the cost of operating, maintaining, repairing, or retiring a plant. Using CO2 super critical dynamos changes the picture some irregardless of the heat source. Having a direct conversion scheme changes the picture profoundly. No steam plant is required, cooling considerations are much easier without needing to generate a relatively hot and challenging and expensive gas (steam or CO2) handling system. This is somewhat tangential but is very important in consideration of system costs.

I'll add that after more than a decade of following this stuff, my impression of the ranking of approaches to reliable electrical production based on desirability from cost concerns- money and environmental, is first P-11B fusion in small machines, then large, followed by D-D fusion, solar/ wind, D-T in smaller machines, thorium and liquid salt fission, D-T fusion in large machines similar to ITAR, and finally classical fission. Aneutronic fusion is so attractive. I think Helium3 is an extremely unlikely candidate due to the lack of the fuel. The same can be said for tritium primary fusion. though expensive and unproven methods may circumvent this. I terms of the holy grail , P-11B fusion in small machines is the best by far. A huge effort should be directed towards it. Solar is another fusion reactor that may surpass fission and ITER schemes as improvements in cost and efficiency, and of course storability are pursued.

What worries me most is D-D fusion in small machines. The proliferation risk from such might be orders of magnitude worse than the large and very expensive fission reactors. This is especially true if D-D fusion becomes easy to implement primarily, instead of depending on the use of pirated large fission plants that have been foolishly made available to nuclear weapon wannabes.

Dan Tibbets
To error is human... and I'm very human.

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Re: Fission news(I know blasphemy )

Postby RERT » Mon Mar 06, 2017 10:55 am

...first P-11B fusion in small machines, then large, followed by D-D fusion, solar/ wind, D-T in smaller machines, thorium and liquid salt fission, D-T fusion in large machines similar to ITAR, and finally classical fission....

Interesting list, and seems sensible. Solar/Wind without batteries is more of a net-demand reduction technology, and is only a competing generation technology with good enough batteries. Hard to place the latter on the list until the batteries are understood, but probably high up there.

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Re: Fission news(I know blasphemy )

Postby RERT » Mon Mar 06, 2017 11:04 am

This response from Thorcon on the 'drain event'.

After a drain , the normal procedure is to use one of the drain tank's three fluidic pumps to transfer the fuelsalt to either

a) back into this Can's primary loop, or
b) to the other Can in this PMOD's, or
c) to the PMOD's fuelsalt transfer cask.

A drain is not a meltdown in any normal sense of the word. While a drain is used in some casualties to put the fuelsalt in location where there is no chance of criticality and the decay heat can be removed passively, it is also the first step in transferring used fuelsalt to either the other Can in the PMOD or to the transfer cask. A drain is a standard operating procedure, albeit one that normally takes place only once every 4 years per PMOD.

Fluidic pumps are quite reliable. They have no moving parts. And the compressor that drives them is in the silo hall where it is easily accessible for maintenance and replacement. And we have triple redundancy.

But if we cant pump the fuelsalt out of the drain tank, the crane is speced to lift both the Can/FDT and the salt. The problem here is that the additional radioactivity in the Can/FDT will require special procedures during the transfer for the silo to the Canship and at the Can Recycling facility end.

Hope this helps,

(reformatted by RERT)

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Re: Fission news(I know blasphemy )

Postby Maui » Thu Jan 04, 2018 5:48 am

Maui wrote:Is Yucca really the primary hurdle for nuclear?

It seems reality has come back with a different verdict than the answer I got to this question earlier this year. (edit: last year!) The only two ongoing US nuclear projects (approved in 2009 and 2012) bankrupted builder Westinghouse due to billions in cost overruns.. Recently Georgia PUC elected to push forward on their project despite 5 years and $9B in overruns. South Carolina, OTOH, is abandoning their project and refunding customers an average of $1K in extra fees intended to have helped finance the project. This, despite being 5 years into construction.

I don’t see any mention of regulation tying up these projects which I would assume cleared most of those hurdles when they began. Perhaps Westinghouse just f’d this up, or there are better designs that should have been used, but it’s hard to argue this calls the economics of fission into question.

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Re: Fission news(I know blasphemy )

Postby RERT » Thu Jan 04, 2018 7:53 am

I think the assumption that regulation was cleared up-front is questionable. The assertion from Thorcon was that 1970s nuclear costs were lower than coal. That must mean currently many billions of costs per plant are due to regulation, which can hardly be from a careful review of plans. More likely every last component being over specified, tested, certified, and tracked - though that's just my speculation. Someone involved might shed more light.

Nuclear companies might be on a sticky wicket with the public and the regulator if they cited (well known) regulations as the cause of overruns.

Tom Ligon
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Re: Fission news(I know blasphemy )

Postby Tom Ligon » Thu Jan 04, 2018 6:43 pm

In our neck of the woods, we have an abundance of gas from fracking. The most recent powerplant to be built in our area is natural gas fired. This has, if I understand it, a mix of steam and gas turbines. The gas turbines are like turboprop engines ... can throttle up our down quickly.

Compare this to nukes, with reactor periods of half a day or more. These typically just run steady to supply base load. But we're getting more and more wind turbines on line here. In South Carolina, I've recently noticed a proliferation of old agricultural fields covered with PV panels. Nuclear is not a good balance for these. Natural gas is. I suspect the economics of fission plants, already not great, are not being helped by the load-management hurdles the renewable part of generation are creating.

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Re: Fission news(I know blasphemy )

Postby RERT » Fri Jan 05, 2018 2:00 pm

Can't argue with that. Subtract volatile renewables from volatile demand, and you get smaller demand which is more volatile. Must be bad for any base load supply which is not easy to adjust.

Ironic that renewables are working against carbon-free nuclear power. You can probably work up an argument that base load can shrink more than the average contribution of renewables. In places where all of base load is nuclear, that might make the addition of renewables increase carbon intensity...

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