Energy From Thorium Discussion Forum

It is currently Dec 15, 2017 2:58 pm

All times are UTC - 6 hours [ DST ]




Post new topic Reply to topic  [ 11 posts ] 
Author Message
 Post subject: I2S-LWR
PostPosted: Nov 09, 2014 8:24 am 
Offline

Joined: Feb 28, 2011 10:10 am
Posts: 347
A new design for future PWRs has been presented by the Georgia Institute of Technology, in collaboration with the University of Cambridge:

Integral Inherently Safe Light Water Reactor (I2S-LWR)

It is interesting that the design has been influenced by the modularity of the SMRs, although the power output will be around 1 GWe. Another interesting feature is the use of new fuel: U3Si2 . The team from Cambridge is also looking into using thorium in this reactor. I wonder whether this reactor could become a LWR thorium breeder.

links:

http://www.neimagazine.com/features/fea ... r-4253617/

http://www.cam.ac.uk/research/news/camb ... ear-design


Top
 Profile  
 
 Post subject: Re: I2S-LWR
PostPosted: Nov 09, 2014 8:35 am 
Offline

Joined: Jun 19, 2013 11:49 am
Posts: 1494
Its not that innovative apart from the Uranium Silicide fuel - which I will look more into.


Top
 Profile  
 
 Post subject: Re: I2S-LWR
PostPosted: Nov 09, 2014 11:20 am 
Offline

Joined: Oct 28, 2013 12:24 am
Posts: 256
Quote:
Reactor pressure vessel size : Same size or smaller than current large PWRs.


If they really can do it, this is impressive. I though this type of integral design with large PWRs was nearly impossible since the construction of a big vessel would be very difficult, so this is very interesting.

Having the borated water tank in the RPV is an improvement in safety since it avoids the break of the pipe between the RPV and the borated water tank.

However the benefits in safety for primary line breaks is maybe not that great. Large primary pipe breaks with PWRs are very improbable and modern passive loop designs can deal with these breaks. This integral design must also deal with water leaks anyway although this accident is less probable and will probably be less severe.

The DRAC loop can maybe run constantly and do not need Instrumentation and Control and openning of valves, which is a good thing. But they must deal with loss of water in the DRACS (in case of pipe breaks or overpressure in the DRACS). If the level of water is low in the RPV the DHX can be dewatered. The containment must be passively cooled anyway and they must provide water to the core in case of water leaks in the primary loop. So this kind of DRACS is maybe not absolutely needed but it avoids pressurization of the containment if there is no leaks at all.

I think the main improvement will be in the economical domain. They can maybe put the flashing steam drums outside of the containment, the containment may be less large than for current PWRs. They can be inspired by the passive cooling system of the ESBWR.


Top
 Profile  
 
 Post subject: Re: I2S-LWR
PostPosted: Nov 11, 2014 4:39 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5056
Thanks for the references Camiel. This is a very interesting design.

I like the integral design combined with high power output and am quite amazed like some others here that they can pull this off at all.

I imagine the pressure vessel is enormous and very thick even with higher power density core.

Flashing steam is a nice simplification but a bit old fashioned. This is rarely used in modern designs because of issues with carryover of water to the steam turbine and generally lower steam quality lowering the efficiency.

Uranium silicide fuel is very promising and has been proven in smaller plate type reactor fuel. The silicon improves oxidation resistance and likely also improves the phase stability of the uranium (reduce swelling). Very high HM density is possible with this fuel.

Still the FeCrAl cladding is going to be a massive devourer of neutrons. Also while it reduces hydrogen generation it sure isn't zero if there's a heatup and it does have a threshold where the steam reaction runs away, if a loss of cooling accident occurs very high temperares are seen. There is also a bunch of hydrogen generated from damaged fuel debris, from radiolysis due to high LET alphas and such. Plus the uranium silicide fuel will generate more hydrogen than UO2 upon contacting water in a core melt accident. This suggests this design has difficulty with beyond design basis accidents where fuel damage occurs. It would still need the containment that traditional PWRs need. One of the attractions of the NuScale reactor is that its containment is integral to the module as well so the bay the modules is in is an ordinary bay in a simple shield building rather than massive pressure containment.

Like Fab I don't think LOCA is all that big a deal. It is very unlikely if enough safety margin is employed, if it does occur there are redundant injection systems in LWRs. If those also fail then the high reliability depressurization system followed by emergency fire water injection would terminate the accident progression. All of the systems would have to fail which is just very unlikely. Loss of heat sink type events are more serious and the passive systems help a lot. Still I don't really see a big gain in safety or economics over say AP1000. It would need similar containment and shield building and foundation, all big cost items. The reactor equipment itself is usually on time and on budget, its all the other stuff like civil works, plant electrical etc where the big cost overruns are seen. So just taking a different reactor design without a whole new approach to major construction etc. seems to me as a case of missing the point.


Top
 Profile  
 
 Post subject: Re: I2S-LWR
PostPosted: Nov 11, 2014 6:22 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5056
Hmm, they are using a printed circuit heat exchanger (PCHE) for the steam generator, and that appears to be the major reason why this integral design works on such a high power output level. PCHE SGs are around 1/10th or less the size of U-tube SGs as used in PWRs.


Top
 Profile  
 
 Post subject: Re: I2S-LWR
PostPosted: Nov 11, 2014 3:34 pm 
Offline

Joined: Feb 28, 2011 10:10 am
Posts: 347
I did find somewhat more information on the web. They are also looking at UN fuel in SiC cladding, as a secondary choice (see attachments). The height of the integrated vessel is less than 22 m. , which means that it is easily transportable as module(s). Quite impressive for a 1 GWe unit.


Attachments:
I2S-LWR(BPetrovic)_HND_IEEE_2014-02-10.pdf [1.89 MiB]
Downloaded 147 times
9-Petrovic.pdf [430.05 KiB]
Downloaded 209 times
Top
 Profile  
 
 Post subject: Re: I2S-LWR
PostPosted: Nov 11, 2014 4:26 pm 
Offline

Joined: Oct 28, 2013 12:24 am
Posts: 256
Thanks for the references Camiel.

Quote:
Hmm, they are using a printed circuit heat exchanger (PCHE) for the steam generator, and that appears to be the major reason why this integral design works on such a high power output level. PCHE SGs are around 1/10th or less the size of U-tube SGs as used in PWRs.


One of the main advantages of PWRs over BWRs is that we have physical separation between the reactor and the turbines thanks to the steam generators. How do perform a PCHE in that domain ? Is the barrier stronger or not ?


Top
 Profile  
 
 Post subject: Re: I2S-LWR
PostPosted: Nov 17, 2014 4:16 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5056
fab wrote:
Thanks for the references Camiel.

Quote:
Hmm, they are using a printed circuit heat exchanger (PCHE) for the steam generator, and that appears to be the major reason why this integral design works on such a high power output level. PCHE SGs are around 1/10th or less the size of U-tube SGs as used in PWRs.


One of the main advantages of PWRs over BWRs is that we have physical separation between the reactor and the turbines thanks to the steam generators. How do perform a PCHE in that domain ? Is the barrier stronger or not ?


The PCHE is a much stronger barrier than tubular exchangers. This is due to a combination of autogenous, solid state (diffusion) welding as the plate to plate welding, a very low design stress (high thickness to diameter ratio) and lack of thin fusion welds for pressure containment (header/plenums use thicker welds).

The PCHE also has a lower heat flux through the plates which means less issues with dryout, critical heat flux and the like.

Some worry about thermal stresses because of the rigid nature of PCHEs, but it is possible to use geometry to our advantage here and make the PCHE deform in a benign way rather than fail upon thermal stress.


Top
 Profile  
 
 Post subject: Re: I2S-LWR
PostPosted: Nov 19, 2014 11:26 pm 
Offline

Joined: Oct 28, 2013 12:24 am
Posts: 256
Thanks for the response Cyril.

Can we inspect a PCHE ? It seems difficult with all these ultra small channels.


Top
 Profile  
 
 Post subject: Re: I2S-LWR
PostPosted: Nov 20, 2014 10:06 am 
Offline

Joined: Jul 14, 2008 3:12 pm
Posts: 5056
fab wrote:

Can we inspect a PCHE ? It seems difficult with all these ultra small channels.


It is possible to use ultrasonic resonance type measurements, I'm researching a high penetration, high resolution technique right now but better if I don't talk about it.

PCHEs are a bit different than tubular exchangers in this respect. The leak probability is greatly reduced. The experience with heat exchangers is that they leak in specific places, such as thin fusion welds, gaskets/seals and such. PCHEs avoid these altogether so they eliminate the primary leak paths. If a leak does occur, it will be small because of the small channel size, and also the compactness and modular nature of PCHE means that you can simply isolate a leaking module. This is similar to tube plugging in tubular exchangers, but better since you don't have to open the HX...


Top
 Profile  
 
 Post subject: Re: I2S-LWR
PostPosted: Nov 20, 2014 1:38 pm 
Offline

Joined: Oct 28, 2013 12:24 am
Posts: 256
Thanks.

Quote:
I'm researching a high penetration, high resolution technique right now but better if I don't talk about it.


So you work on PCHEs, I understand that you can't speak about it. Good luck for your work.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 11 posts ] 

All times are UTC - 6 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group