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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 16, 2014 9:38 pm 
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I thought I'd calculate the pluto exposure, because it didn't sound that bad to me. Say that the SOP is to jettison a reactor in a crash. It falls at the speed of sound (345m/s), and is designed to penetrate 30 meters into the dirt, and thereby become more-or-less passively safe.

I have to eat crow. The result is surprisingly nasty. If you were standing 100m from the reactor's crash site at the time of the crash, you'd get 40 Grays. (Afterward, you'd be fine unless you stood on the lip of the hole.) This is a lethal dose for half the population.


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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 17, 2014 2:49 am 
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Nuclear power is best left to power plants and ships. Cars and aircraft are just too small for the purpose.
I have been posting in favor of floating power plants. Now the same idea has come from elsewhere.
http://www.theverge.com/2014/4/16/56209 ... -disasters


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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 17, 2014 6:57 pm 
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"floating power plants."


I realize the Russkies are building some form of these. However, I wonder how practical an idea this really is. Big nuke plants in the US have big staffs. Will the majority of the staff work ashore and only a minority travel to the plant?

How about them transmission lines, eh? Have you ever seen many undersea 345 kV lines? How reliable are they going to be?

Maybe a few fixes would have prevented Fukushima. Diesels in a high watertight room and a higher seawall perhaps. Moving the entire plant out to sea may be a bit of an over-reaction.

It seems like a plant sitting in the water is like a sitting duck for all kinds of things. It could be great target practice for some kinds of nasty people. Greenpeace could take their boat and get lots of publicity attacking the nuke plant.

On the other hand, if the plant was built right and warmed surrounding waters it could be a great spot for fish farming.

Even the dreamers at MIT realize it ain't gonna happen in the US. :P


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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 17, 2014 7:44 pm 
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Fitting a plant onto a ship requires all sorts of compromises in the design that we can really do without.

You can't simply throw masses of concrete and cheap cast iron/concrete radiation shielding at every problem.

A 1500MWe class reactor masses something approaching 300kT at minimum.


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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 17, 2014 11:25 pm 
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E Ireland wrote:
Fitting a plant onto a ship requires all sorts of compromises in the design that we can really do without.

You can't simply throw masses of concrete and cheap cast iron/concrete radiation shielding at every problem.

A 1500MWe class reactor masses something approaching 300kT at minimum.

They do it all the time, and make them robust enough to survive combat. Putting a big one in a spar-bouy the size of an oil rig would be a piece of cake.

As to the transmission lines, they exist in a lot of places and are quite reliable.

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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 18, 2014 5:09 am 
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Good idea, but only in conjunction with a waste burning Liftr right next to it. So that everybody is happy. :lol:


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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 18, 2014 5:19 am 
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"As to the transmission lines, they exist in a lot of places and are quite reliable."

I wouldn't say all the time, but you are right there are submarine cables.

http://en.wikipedia.org/wiki/High-voltage_direct_current

You have the extra complication of having to build a rectifier inverter station because it would end up as DC.

They better be reliable because they sure would be hard to repair.

Only the military can afford such a thing these days. It ain't gonna happen.

Maybe,.....We can get somebody to build a small Thorium pilot plant in the desert of Idaho, but that's the best you can ever hope for in the next 20 years.

It would take 20 years to license an offshore facility.


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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 18, 2014 9:35 am 
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KitemanSA wrote:
They do it all the time, and make them robust enough to survive combat. Putting a big one in a spar-bouy the size of an oil rig would be a piece of cake.


Naval reactors cost many times more than civil plants even with current runaway costs. This is why every major navy does not have an all nuclear surface fleet.


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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 18, 2014 10:12 am 
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E Ireland wrote:
KitemanSA wrote:
They do it all the time, and make them robust enough to survive combat. Putting a big one in a spar-bouy the size of an oil rig would be a piece of cake.


Naval reactors cost many times more than civil plants even with current runaway costs. This is why every major navy does not have an all nuclear surface fleet.
Naval reactors cost as much as they do for a goodly number of reasons that wouldn't apply to a comercial NPP, that survivability being amoung them. But being designed to be refueled every 20 years instead of every two makes a difference too.
Lets face it, EVERYTHING the navy buys is much more expensive than the civilian countrparts, even lap-top computers.

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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 18, 2014 8:16 pm 
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In this thread, we started discussing the small thorium MSR but moved afar. We have found that Smallest reactor cores are thorium. However you should not have a solid throwaway moderator. Go un-moderated or use water as moderator-coolant.
To do something new, have a water moderator-coolant with molten salt if you can manage the thermal shock.


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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 19, 2014 1:12 pm 
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jagdish wrote:
have a water moderator-coolant with molten salt if you can manage the thermal shock.


Jagdish, can you explain this in more detail please, I am not understanding your idea. Thanks.


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 Post subject: Re: Smallest Thorium MSR
PostPosted: Apr 20, 2014 3:02 am 
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edpell wrote:
jagdish wrote:
have a water moderator-coolant with molten salt if you can manage the thermal shock.


Jagdish, can you explain this in more detail please, I am not understanding your idea. Thanks.

Put liquid nuclear fuel in the fuel space of a water tube boiler. It requires moderated neutrons for burning it.
Put some Be-Pu in fuel for neutron generation. The neutrons will be moderated by water in tubes and move back to fuel for multiplication.
The fuel should be enriched with extracted Pu, enough for thermal spectrum but not for fast spectrum. The fuel away from water tubes will eat up excess neutrons for conversion to fissile U-233 or Pu-239. This has to be designed to balance the loss to absorption by fission products. This can be done better by thorium, which can be added as in the DMSR.
This boiler can be the core of the rector. the other requirements can be added in the manner of nuclear power plants.


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