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42 comments on On the hazards of ignorance of thermodynamics

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The_Dude on October 8, 2008 - 9:57am Permalink | Subthread | Parent | Comments top

Very true, not proven. Like most engineering fields, advances in power cycles are getting held back by materials issues.

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Engineer-Poet on October 8, 2008 - 10:43pm Permalink | Subthread | Parent | Comments top

If you think that companies which currently build and sell combustion turbines running at 1380°C firing temperatures would have any difficulty cranking out inert-gas turbines taking a measily 850°C input stream, you're kidding yourself.

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The_Dude on October 9, 2008 - 10:22pm Permalink | Subthread | Parent | Comments top

Well the Helium one should be ok. But you have to remember that the people who sell these turbines, design them to break even after selling a lot of them. There's an inherent resistance to a new working fluid or different working conditions. I heard GE sells a new aircraft engine with the break-even time frame on the order of 5-10 years. I bet GE Energy has lost money on a couple of their combustion turbines. That requires a lot of confidence in the power plant design and market.

A CO2 turbine in the 500-600 C range for a sodium cooled reactor would be a materials nightmare.

The materials problem with the HTGR is the nuclear fuel. Fission product leakage plus the graphite in the fuel might turn the turbine into a combustion turbine if air ever leaked in.

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Engineer-Poet on October 10, 2008 - 11:23pm Permalink | Subthread | Parent | Comments top

But you have to remember that the people who sell these turbines, design them to break even after selling a lot of them. There's an inherent resistance to a new working fluid or different working conditions.

Offsetting this are the mild operating conditions (old, cheap materials and processes will be more than sufficient) and large potential volume.  Certifying one turbine as part of a power reactor (especially one which doesn't compete with other designs for fuel, using e.g. spent PWR fuel and/or thorium) could sell 100 GW of capacity or more in the USA alone.

A CO2 turbine in the 500-600 C range for a sodium cooled reactor would be a materials nightmare.

Sodium is a materials nightmare.  Molten fluorides appear to be much easier to handle.  Neon is more expensive than CO2, but unreactive and with a much more favorable set of thermodynamic properties (ratio of specific heats = 1.67).

The materials problem with the HTGR is the nuclear fuel.

Silicon carbide is sufficient to protect carbon-carbon against re-entry heat on the Shuttle.  It will keep HTGRs from going all Chernobyl on us even if the reactor fills with air.

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Cyril R. on October 14, 2008 - 8:34am Permalink | Subthread | Parent | Comments top

If you think you can get away with comparing apples and oranges like that on this site, you're kidding yourself.

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42 comments on On the hazards of ignorance of thermodynamics

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