Energy From Thorium Discussion Forum

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PostPosted: Feb 23, 2014 11:06 am 
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One intriguing option, that we've discussed on the forum before, is to insulate the vessel on the inside. This works particularly well for drain tank concepts. It allows the vessel to operate at an already qualified nuclear vessel temperature, so regulatory speaking you don't need a new nuclear code case. Technically it eliminates a number of problems ranging from thermal creep to high temperature neutron embrittlement. From a safety viewpoint it prevents vessel overheating during transients. The only real downside is, passive cooling through the vessel (if you want that) doesn't work so well anymore. Which is why it works better for drain tank concepts.


Well if you don't want to use drain tanks ( which is maybe a good thing economically for a low power density reactor) and isolate the vessel, I guess you can still use DRACS ; or PRACS in a buffer salt as you already said it before in an other tread.

Thanks for all your responses Cyril, but there is one thing I don't understand : if it's possible to use stainless steel at 600°C for the vessels and the other main components, why don't I see it more often ? I mean all the documents I read about MSRs speak about Hastelloys and sometimes Molybdenum alloys, Carbides and Carbon composites for high temperatures. It's pretty unusual to see mention of stainless steel for the vessel ( I just saw it in Dr. Leblanc's presentations and a few other papers...)


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PostPosted: Feb 23, 2014 4:50 pm 
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This is because stainless steel costs more letters than Hastelloy N. So for a paper reactor, stainless steel costs more paper. And boy, do we've got paper MSRs.

More seriously though, the cost of the reactor metal itself is only a small fraction of the total plant cost. So look for other advantages than cost alone... stainless has a lot going for it that have nothing to do with raw $/kg material.

The recent PB-FHR mk1 design uses SS316 as major reactor vessel and HX material, so it seems more people are coming over to the low allure of cheap and common materials. :lol:


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PostPosted: Feb 24, 2014 12:53 pm 
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:P thanks


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PostPosted: Feb 24, 2014 1:47 pm 
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SS also has a lower op temp than H-N. That is why it becomes viable at the lower temps of the subject line.

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PostPosted: Feb 24, 2014 2:36 pm 
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KitemanSA wrote:
SS also has a lower op temp than H-N. That is why it becomes viable at the lower temps of the subject line.


What are you talking about?


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PostPosted: Feb 24, 2014 4:05 pm 
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Cyril R wrote:
KitemanSA wrote:
SS also has a lower op temp than H-N. That is why it becomes viable at the lower temps of the subject line.
What are you talking about?
Every time I see the peak operating temperature of Stainless Steel, it shows up LOWER than Hasteloy-N. So reducing the peak temperature of a reactor would allow SS to be used rather than requiring H-N. No?

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PostPosted: Feb 24, 2014 4:14 pm 
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KitemanSA wrote:
Cyril R wrote:
KitemanSA wrote:
SS also has a lower op temp than H-N. That is why it becomes viable at the lower temps of the subject line.
What are you talking about?
Every time I see the peak operating temperature of Stainless Steel, it shows up LOWER than Hasteloy-N. So reducing the peak temperature of a reactor would allow SS to be used rather than requiring H-N. No?


SS is fine for 700C. Hastelloy N actually has a higher strength gain for going to lower temperatures. At 700C the allowable service stress of SS316 is similar to Hastelloy N.


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