Energy From Thorium Discussion Forum

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PostPosted: Aug 07, 2015 10:06 am 
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Normal construction method for a built up gun barrel is to either heat-shrink the outer tube onto the inner one or to expand the inner tube by pushing a mandrill through.
The former sounds far more practical in this case.


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PostPosted: Aug 07, 2015 11:01 am 
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Cyril,
Think concentric cylinders. You heat one (increasing the diameter), slide/press it over the cool cylinder, allow to cool, repeat with additional cylinders until you have built up to required material thickness for pressure needed to resist. The total assembly can then be further heat treated if needed after assembly is complete. The cooling cylinders add compression to the inner cylinders helping to resist the design pressure. The top and bottom of the reactor could be sealed/welded against every cylinder.

I like the fruit roll up reactor design.

mike


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PostPosted: Aug 07, 2015 1:10 pm 
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michaelw wrote:
Cyril,
Think concentric cylinders. You heat one (increasing the diameter), slide/press it over the cool cylinder, allow to cool, repeat with additional cylinders until you have built up to required material thickness for pressure needed to resist. The total assembly can then be further heat treated if needed after assembly is complete. The cooling cylinders add compression to the inner cylinders helping to resist the design pressure. The top and bottom of the reactor could be sealed/welded against every cylinder.

I like the fruit roll up reactor design.

mike


Hmm, ok. So each cylinder is closed in itself. I guess the advantage of using a single coiled up sheet of metal is that we avoid welds that we can't ever see or inspect again. But this idea sounds promising for the bottom and top vessel head. Just add more caps. If the caps are thin enough they can be mass produced in a die press line. This would make it easy to puncture holes for control rod drives, as well. Each cap could be welded circumferentially. This sounds like something that would be possible to automate. Like, panel manufacturing for cars or saucepans.


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PostPosted: Aug 07, 2015 2:48 pm 
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For the interior weld, Would you weld on the inside of the of the spiral to the next leg of the spiral or would you weld to the back of a mandrel/liner and wind the spiral around the mandrel?
If you notched the exterior surface of the liner your spiral would lay flush with the mandrel and would fix the liner to the spiral.
The thermal expansion of the metal would have to be accounted for, may have to wind the spiral at operating or higher temperature.
Any thoughts on fusing the spiral across the full face of the plates as it is formed with friction welding/ultrasound welding? Oscillating wedge/tool at the union of the two faces of the plate, friction welding the interior and exterior of the spiral together.


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PostPosted: Aug 07, 2015 3:51 pm 
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I'm thinking of using the maraging steel with an inner stainless steel liner. That inner liner would be prefabricated completely and would form the roll on which the spiral plate coil is rolled onto. That way the maraging steel weld requirement is low. Be interesting to check the stresses, it may need a special weld overlay on the ends of the spiral. I'm thinking everything is welded by semi-automatic/automatic TiP-TIG welding. Friction stir welding is cool, but needs a lot of hold down forces and resulting equipment. Sort of tricky to do compared to a simple, idiot-proof TiP-TIG technology.

Then again perhaps with this roll method we might as well use A508/A533 standard RPV grade steel. Thickness is not so difficult anymore...


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PostPosted: Aug 07, 2015 3:53 pm 
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michaelw wrote:
The thermal expansion of the metal would have to be accounted for, may have to wind the spiral at operating or higher temperature.


Good point! Winding at higher temperature would be interesting. Sort of like a prestressed steel vessel, where vessel overheating actually reduces the stress...


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PostPosted: Aug 08, 2015 9:35 am 
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Re: Super Bainite
I've been doing some more reading on the Charpy impact test. I understand how it is done. What I don't understand is how it is reported. You may want to evaluate Super Bainite on your own. I don't know if I reported the right number. Super bainite is being promoted for armor applications, you would think that it would have high fracture toughness along with high strength.

Mike


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PostPosted: Aug 08, 2015 3:51 pm 
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Fracture toughness and impact toughness are not quite the same thing. Impact toughness, as measured by Charpy tests, is a measure of the energy absorbed during fracture. Fracture toughness is a measure of the ability of a material to resist crack propagation of an existing crack or other imperfection. One big difference between the two is the strain rate. Another big difference is that impact testing measures the energy going into the fracturing whereas fracture toughness testing measures the stress before fracturing actually occurs.

For armor you definately need high impact strength. For nuclear pressure vessels, fracture toughness is more important, as the vessel is well protected by all kinds of thick shields against impact. It has always seemed a bit odd to me that the codes focus on impact strength. Some is needed for servicing the reactor vessel (can't have a vessel break when a worker is doing repair, replacement, disassembly or inspection on it). But not that much is needed unless sabotage is considered (it isn't considered quantitatively in current codes, to my knowledge).

Maybe we will be interested in a lower grade bainate like a flash bainate steel. But the fracture toughness is well below 100 MPa/sqrtm so it isn't really a fair comparison with A508/A533.


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PostPosted: Aug 12, 2015 9:48 am 
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Cyril,
Haynes 556 looks interesting for the super alloy reactor with no cladding. weldable, oxidation (chemical) resistant and reasonable toughness. behavior in a neutron environment?
http://www.haynesintl.com/pdf/h3013.pdf
Has ASME vessel code section 1 to 650C. 129Mpa max allowable stress at 371C.


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PostPosted: Aug 12, 2015 12:39 pm 
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michaelw wrote:
Cyril,
Haynes 556 looks interesting for the super alloy reactor with no cladding. weldable, oxidation (chemical) resistant and reasonable toughness. behavior in a neutron environment?
http://www.haynesintl.com/pdf/h3013.pdf
Has ASME vessel code section 1 to 650C. 129Mpa max allowable stress at 371C.


Looks like it is more of a high temperature alloy. The low temperature strength is worse than regular A508/A533 RPV steel.


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