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 Post subject: Re: High Pressure BWR
PostPosted: Aug 01, 2017 7:51 am 
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Sure that should fit fine. There's a shield wall and some space for steam flow in a loca (between lower drywell and upper drywell). The shield wall would be integrated with the cast iron (or concrete) and the loca drywell communication could be via embedded pipes. Ditto for the DW/WW vent lines.

This would probably allow a very large uprating with the ESBWR size containment. 5000 MW would be rather easy. If you can get 39% gross efficiency it would be 1950 MWe gross. Probably 1850 MWe net. That's a serious machine!

A concrete version (PCRV) would be interesting too, as it would be easy to integrate the reactor vessel with the containment structure - don't need reactor vessel supports. It could all be made of steel plate concrete.

Cast steel may also be an interesting option; it is tougher and stronger than cast iron and allows easy welding of pipes and nozzles (this is a tricky area with PCRV).


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 Post subject: Re: High Pressure BWR
PostPosted: Aug 01, 2017 5:59 pm 
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At that point you are limited by the availability of suitably sized turbine plant.

I believe Areva and General electric only advertise up to ~1900MWe.

Unless you went Sizewell B and had two turbine trains.
Or built some sort of bespoke quarter speed [750rpm 8-pole] machine.


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 Post subject: Re: High Pressure BWR
PostPosted: Aug 02, 2017 8:21 am 
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E Ireland wrote:
Resistance to aircraft strikes is the important factor.
Varies from 44MPa/(m^0.5) to 100+

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.


I think the Hualong One splits the problem with an outer, concrete shell, to take aircraft impact. The inner shell is designed to withstand internal events, and I assume a collapsing outer shell.

This increases the size of the unit, but the outer dome is relatively low cost and simple, though massive. It should also make analysis simpler.


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 13, 2017 9:10 am 
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There's one other benefit to higher steam pressure that I hadn't realized before - higher steam density. This means fewer steam lines, relief valves, depressurization valves, etc. Higher temperature and pressure also means higher heat transfer rates - so ditto for cooling systems design.

According to my steam tables, a 12.5 MPa sat steam pressure would be twice the density as 7 MPa sat steam.

For an ESBWR this would mean 2 instead of 4 main steam lines, 2 isolation condensers rather than 4, 2 DPVs instead of 4, 9 SRVs instead of 18, etc.

That would easily offset the increased cost due to thicker walls. Not to mention less stuff to fail or service!

Looking at this stuff:

http://www.siempelkamp.com/fileadmin/me ... _09_EN.pdf

It suggests you can just cast an ESBWR size pressure vessel out of 3 or 4 pieces and ring weld the pieces. Castings are pretty common in the nuclear industry already, even for critical components such as safety grade, nuclear grade, high pressure valve bodies. Likely a cast equivalent of a nuclear grade steel (A508 or similar) would meet all ASME requirements for fracture toughness, etc.


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 14, 2017 1:19 am 
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We could use a calandria with bigger tubes for water and main drum for liquid thorium based fuel. We could flush out the neutron absorbing gases and keep on adding 20% leu as required. We could change the fuel when the reactor is closed for periodic repairs such as retubing. I am sure this will reduce cost.


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 16, 2017 2:57 pm 
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Looks like tese guys have the right idea:

http://proceedings.asmedigitalcollectio ... id=1573553

Too bad its paywalled...


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 16, 2017 3:05 pm 
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Its even paywalled from my uni access point....


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 16, 2017 4:32 pm 
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E Ireland wrote:
Its even paywalled from my uni access point....


Typical ASME "ivory tower" syndrome...


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 16, 2017 6:37 pm 
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Cyril R wrote:
E Ireland wrote:
Its even paywalled from my uni access point....


Typical ASME "ivory tower" syndrome...

Considering my course is MSc Nuclear Science and Technology I might raise this with the course office.

(But I also have something I am working on that can apparently make 42% gross with a Sizewell B type PWR.... although I am not sure I really believe it)


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 17, 2017 8:40 am 
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42% with PWR, that does aound too good to be true. Then again US APWR got 39% and i'm sure there is more to gain with innovations...

Also think that Tsiklauri et al are too pessimistic on efficiency. 42% for 150 MPa steam of 550c is not stellar, esp. For a 1500 MWe class TG.


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 17, 2017 1:14 pm 
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It's about what the AGR managed 40 years ago with similar steam conditions.


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 17, 2017 2:40 pm 
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E Ireland wrote:
It's about what the AGR managed 40 years ago with similar steam conditions.


Exactly! Various improvements have since been made, esp in the lower pressure turbine, steam dryers, bleed systems, blade/bucket design, etc


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 18, 2017 8:37 am 
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Wouldn't the pebbles likely be able to withstand attack from supercritical water?
If so, wouldn't that mean we should be looking at an SCWR in that performance range - which would have nearly 50% efficiency if coal units with 550C steam are anything to go by.


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 18, 2017 10:57 am 
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E Ireland wrote:
Wouldn't the pebbles likely be able to withstand attack from supercritical water?
If so, wouldn't that mean we should be looking at an SCWR in that performance range - which would have nearly 50% efficiency if coal units with 550C steam are anything to go by.


Yes, almost certainly, SiC withstands supercritical conditions, even in rad field. But there are some other components in there too - core internals. Unless these can be made of SiC composite, there are all sorts of questions regarding core flux levels of radiation + supercritical conditions. The radiolysis products will be different, and solubilities change with going from water to supercritical fluid. So far results on metallic internals are not good, very high levels of stress corrosion is seen. From a safety systems viewpoint, removing the recirc in the core does mean loss of feedwater is a more serious transient. So that will have to be evaluated. Otherwise it's a pretty promising concept.

Of course, the MFE particle fuel guys are into this as well, the best paper I got from them is attached, a really nice read I found:

Attachment:
SCWR MFE 1500.pdf [693.12 KiB]
Downloaded 21 times


Pretty clever doing a tube-filter style radial flow in the core, that means low pressure drop through the particle bed (short flow path length), plus nice cold feedwater in between the assemblies for moderation. Cooling the vessel with the feedwater is clever too, though most SCWR guys and gals figured that trick out some time ago...

I've looked at casting and I think a cast steel (same RPV steel as PWRs, but just cast) is very feasible with this size vessel. It could probably be made in one piece so no welds to fail or inspect. Pretty sure Sheffield Forgemasters or Siempelkamp can do this. (recall that forged rings start out as castings, so if you can make a multi hundred ton forged ring you can make an equivalent size casting). Casting would be a lot cheaper too.


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 Post subject: Re: High Pressure BWR
PostPosted: Sep 21, 2017 4:11 am 
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High pressure gets you higher thermal efficiency but also risk and cost. It should be combined with some mitigating factors. Some that I could think of are
A standardised size such as current 500MW reactor.
Intermediate heat transfer with a less volatile moderator. Some hydrocarbon could be suitable. It could make the reactor lighter and safer. High pressures could be confined to steam generator and reactor could work at low pressure. MSR could be developed.


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