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 Post subject: Re: High Pressure BWR
PostPosted: Aug 22, 2014 7:33 am 
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jon wrote:
Any thoughts on the Lightbridge type helical cruciform metal fuel for BWRs? The surface area would be much greater, and the central temperature lower.


Yes, any fuel that is good enough for PWR will work with BWR because fuel conditions are less nasty.

Again though the question is how far you can push power density in a natural circulation design. Could be that less restrictive orificing gets you a lot but I don't know the design space available (anyone have information on the orificing plate in ESBWR?). The ESBWR vessel is already too tall for my tastes, at 27+ meters. Making it taller to get more driving force isn't attractive.

For forced circulation BWRs the sky is the limit basically. It seems especially suitable for Kerena (formerly SWR1000) because that 'only' generates 1250 MWe or so and it is forced circulation yet it has shorter lower pressure drop core like the ESBWR.


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 Post subject: Re: High Pressure BWR
PostPosted: Aug 25, 2014 4:53 am 
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What if you added this non-electrical pump (http://www.fisonic.us) to the BWR to enhance flow without electricity, no moving parts, and only 4 main parts: 1) T shell, 2) Venturi nozzle for mixing, 3) compression nozzle, 4) divergent nozzle, if additional pressure head is needed? Although I have to say that this pump would work better on a low pressure BWR to enhance flow.


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 Post subject: Re: High Pressure BWR
PostPosted: Aug 25, 2014 7:58 am 
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Ed P wrote:
What if you added this non-electrical pump (http://www.fisonic.us) to the BWR to enhance flow without electricity, no moving parts, and only 4 main parts: 1) T shell, 2) Venturi nozzle for mixing, 3) compression nozzle, 4) divergent nozzle, if additional pressure head is needed? Although I have to say that this pump would work better on a low pressure BWR to enhance flow.


This appears to be a typical steam injector or ejector or eductor or whatever it is called. Is the idea here to inject live steam from the turbine bleed system into an injector? This could be very interesting as the steam pipe could be routed from the top so no bottom penetrations, and no moving parts means high reliability.

The question I have is what is the workable range of pressure, temperature and will it work on nearly saturated water or does it need subcooled water? Lindsay may be able to answer these questions.

There are also issues with certain transients where the steam lines are isolated. Then you have no steam for the injector which I think might be a problem in certain ATWS scenarios.


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 Post subject: Re: High Pressure BWR
PostPosted: Aug 29, 2014 11:51 pm 
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Any expert ideas on adding a salt like BeF2 to water to make it a higher temperature reactor at lower pressure? Might help in a PWR.


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 Post subject: Re: High Pressure BWR
PostPosted: Jul 15, 2017 3:19 pm 
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Revisiting this on the basis of information I gained later.

With a Prestressed Cast Iron Vessel you could build a pressure vessel to almost arbitrary sizes and pressures.
And with this TiAlN/AlN coating it would be possible to deal with the increased cladding temperatures of high steam conditions.

360C 185atm would seem to be achievable.


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 Post subject: Re: High Pressure BWR
PostPosted: Jul 18, 2017 4:07 pm 
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Higher pressure without higher temperature probably doesn't buy all that much efficiency improvement.

Probably you can do pretty well with a marginal improvement in BWR conditions, maybe 8 MPa saturated steam conditions. Probably pushing 40% efficiency with optimized large turbine.

Really should push for a SiC-SiC fuel clad for next gen BWRs.


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 Post subject: Re: High Pressure BWR
PostPosted: Jul 18, 2017 4:46 pm 
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Well 185atm with a second reheat would enable the intermediate pressure turbine to have normal BWR live steam conditions at the inlet (285C 75atm)

Which probably gains you significant efficiency gains, remember that we would be talking about 360C steam, not 285C.


Also trying to work out if you can use austempered ductile iron (GRADE 1600 ADI has a compressive strength of 2500MPa... triple GG25 grey cast iron used in most PCIV calculations) to make a ridiculously thin prestressed reactor containment that can still withstand aircraft impacts - then large amounts of heat might be able to simply conduct out of the containment building passively.
And the relatively small size of existing furnaces might not matter too much with the relatively thin sheet castings.


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 Post subject: Re: High Pressure BWR
PostPosted: Jul 19, 2017 9:12 am 
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What kind of efficiency do you think you can get with those steam conditions?

What's the fracture toughness and impact energy of the austempered ductile iron?


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 Post subject: Re: High Pressure BWR
PostPosted: Jul 19, 2017 9:46 am 
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Cyril R wrote:
What kind of efficiency do you think you can get with those steam conditions?


I think pushing 40% is not out of the question, although I would have to do the calculations, but based on simple isentropic analysis of the state points [what is the isentropic efficiency of a modern steam turbine?] it looks very promising.
Cyril R wrote:
What's the fracture toughness and impact energy of the austempered ductile iron?


Varies with grades according to this chart I found on the internet.
The stronger in compression grades are less tough, but even the weakest grade would still be so much stronger than concrete that it almost doesn't matter - the vessels thickness for pressure vessel containment will still be very thin (on order of a few inches).

Resistance to aircraft strikes is the important factor.
Varies from 44MPa/(m^0.5) to 100+

The big problem is the cast iron is only being held together by the prestressing and relatively weak keying on the blocks - so it cant be treated as a big mass like concrete can. But even the keys might allow aggregate tensile strength comparable to the concrete.

EDIT:

The AP1000 Shield building cylindrical section is only 36" thick and is supposed to protect the steel vessel from aircraft impacts. Althoguh the steel content has apparently been redacted.


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