Energy From Thorium Discussion Forum

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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 5:07 am 
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Solar panels would also be a useful comparison. They use lots of metals and chemicals and most are toxic to highly toxic.

Quote:
In the coming years, SVTC estimates that 1.5 billion pounds of solar panel waste containing 2 million pounds of lead and 600,000 pounds of cadmium will be disposed of in California alone.


http://www.motherjones.com/blue-marble/ ... nels-toxic

That lead alone, by LD50 calculation, is enough to kill some 50 million people.

In fact, looking at the global lead metal production of some 10 million tonnes,

http://www.ila-lead.org/lead-facts/statistics

Enough lead around to kill 500 billion people.


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 5:11 am 
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Quote:
Demand for Cs-137 and Sr-90 will be significantly lower than what a decent nuclear program will produce.


True for Cs-137, though strontium titanate RTGs could make a comeback if there is a large cheap source of Sr90. I can especially see a large military and aerospace demand, if the price is right...


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 8:13 am 
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Cyril R wrote:
Quote:
Demand for Cs-137 and Sr-90 will be significantly lower than what a decent nuclear program will produce.


True for Cs-137, though strontium titanate RTGs could make a comeback if there is a large cheap source of Sr90. I can especially see a large military and aerospace demand, if the price is right...


I think safety concerns might forever rule out any RTGs flying (on Earth).

In an ideal (benign) world, I could buy a chunk of shielded strontium titanate and put it in my basement for the winter. Then in summer I'd pick it up and drop it into my swimming pool.

In reality, it will be a controlled material. Perhaps it might be usable for district heating schemes. That said, with abundant MSR electricity, why would you have district heating?


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 9:24 am 
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Well, strontium titanate for consumers I don't think is a good idea. We're talking about a lot of curies and consumers are such irresponsible folk.

RTGs are for small remote power users. Not for district heating. District heating is powerplant territory.

Military apps look important to me. Much better than solar panels with the enormous battery backup need and fragility (can't bunkerize solar panels!). Sr-90 is pretty good, heavier than the Pu238 RTGs but not that much and in some ways safer because PuO2 has some solubility in water.


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 9:30 am 
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I misread that at first as "We're talking about a lot of curries and consumers are such irresponsible folk." :)


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 10:33 am 
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alexterrell wrote:
I misread that at first as "We're talking about a lot of curries and consumers are such irresponsible folk." :)


hmm... curry. :lol:


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 1:22 pm 
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Ok you guys, here's a first graphical attempt at the risk or "what do do when you encounter a spent nuclear fuel assembly!". Can you guess the legend?


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spent fuel gamma dose rate.jpg
spent fuel gamma dose rate.jpg [ 81.13 KiB | Viewed 2409 times ]
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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 3:32 pm 
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Location: Montreal
Cyril R wrote:
For the spent fuel assembly, how about a graph where the bottom of the scale (y axis) is the safe dose level of 2 mSv/day @ 1 meter distance. The line would then reach the bottom at 500 years or so. Then insert a person standing next to a spent fuel assembly to show what this graph depicts. The title, "how long before it is safe to stand next to a spent fuel assembly?". It should not be a log scale, just linear. People don't understand log, plus it is impossible to read from.

Thanks, this is giving me some ideas.....


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 3:40 pm 
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Cyril R wrote:
Ok you guys, here's a first graphical attempt at the risk or "what do do when you encounter a spent nuclear fuel assembly!". Can you guess the legend?

Pretty good. Thanks.
Are the dose rates taken from Cohen's book ? (I have a copy at home, but I'm away until mid-April...)


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 3:56 pm 
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Location: Iowa, USA
alexterrell wrote:
1. Demand for Cs-137 and Sr-90 will be significantly lower than what a decent nuclear program will produce.


Basic supply and demand economics disagree with you. If there is a glut of Sr-90 then I expect new markets to be found for it. I gave an example in a different thread about how fishing boats could find a RTG to be a life saver as it could give heat, light, and communications for someone with a broken motor. I could give a lot of other examples. Titanium lived in the realm of only spacecraft until the price went down to where it was used in aircraft, price drops and it's used to make laptop computers, another price drop and it's used as a building material. Things like back-up cameras and tire pressure sensors were luxuries before but now are standard equipment on all but the cheapest cars.

I expect a Cs-137 would also develop. One company I do contract work for is working on a product that exposes food to RF to kill off diseases, think of it being much like pasteurization for milk but used on fruits and vegetables. This process can also be done with Cs-137 as the radiation source. If Cs-137 gets cheap enough then I expect this market to shift from power hungry microwave generators to Cs-137 devices.

alexterrell wrote:
2. Separating the various chemicals is a non trivial task. An entity which can master this task will also have the capability to produce weapons grade materials.


Advocates of LFTR appear to disagree with you. One of the primary aspects of LFTR that makes it beneficial as an energy source is the difficulty in removing the fissile plutonium from the non-fissile plutonium. SNF contains many plutonium isotopes and there is enough Pu-240 present to prevent simple chemical extraction of plutonium to create weapons grade material. I'm not disputing that an entity capable of this chemical extraction would not also have the knowledge and resources to refine plutonium. What I'm saying is that refining plutonium to weapon grade is a very different process than extracting reactor grade plutonium from SNF.

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Disclaimer: I am an engineer but not a nuclear engineer, mechanical engineer, chemical engineer, or industrial engineer. My education included electrical, computer, and software engineering.


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 4:34 pm 
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It is important to note that when new supply or new technology makes something cheaper,
the loss to the seller is matched by a gain to the buyer. From society's point
of view, this is a big plus. See consumer's surplus. Or for a recent concrete example,
computer chips. We should brag about making stuff cheap, not bemoan it.


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 4:58 pm 
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Problem is, outside niche applications, radioactive materials are more trouble than they are worth. They can't be turned off for one thing.


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 7:07 pm 
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There is always a niche of isolated users not best dependent on the grid. Distributed of renewable power is extendind among right now. A buried RTG can be a less obvious power for them. You have power from fission product waste.
There can be deep boreholes for fission products over the requirement


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 8:46 pm 
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As I've said before - RTGs can't compete with grid electricity. Which leaves only places too isolated for a grid connection - the list of such places shrinks every year thanks to development in Voltage Source Converter HVDC systems. And potentially increasingly high voltage SWER type systems associated with developments in Solid State Transformers related to the former.


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 Post subject: Re: Spent fuel activity
PostPosted: Mar 08, 2015 11:39 pm 
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I looked for published documents that include analyses of radiation dose rates over time, and found one by Canada's NWMO (Nuclear Waste Management Org), which gives this graph of surface dose rates over time -- separately for gamma, beta and alpha radiation.
At ~500 years gamma dose rate comes to about 15 Sv/y.
What would that be at a distance of 1m in air?


Attachments:
CANDU_SNF_surface_dose_rates_NWMO.JPG
CANDU_SNF_surface_dose_rates_NWMO.JPG [ 264.16 KiB | Viewed 2362 times ]
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