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 Post subject: New FHR whitepapers
PostPosted: Aug 09, 2013 3:14 pm 
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http://fhr.nuc.berkeley.edu/?page_id=19

White Paper 1: FHR Subsystems Definition, Functional Requirement Definition, and Licensing Basis Event Identification
White Paper 2: FHR Methods and Experiments Program
White Paper 3: FHR Materials, Fuels and Components
White Paper 4: FHR Development Roadmap and Test Reactor Performance Requirements


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 Post subject: Re: New FHR whitepapers
PostPosted: Dec 15, 2013 6:07 am 
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The large central station, 3400 MWt FHR appears to have become the baseline design for further focus. The PB-AHTR has gotten much less attention and one might be forgiven to think it has been effectively comatized if not dead.

The large FHR design has a lot of issues in my opinion. Here are just a few of them off the top of my head.

The cavity cooling system is an active one. That means the cavity will overheat and damage in the event of a multi day station blackout like Fukushima.

They are also using argon as the cavity insulation gas. Obviously, argon has a neutron activation issue. They appear to be unaware of that.

They claim a thinwalled vessel. However they are going for a vessel of more than 10 meters ID. And made of Hastelloy N cladded Incolloy 800h which is weaker than Hastelloy. Looking at creep rupture curves for Incolloy 800h compared to Hastelloy N, and looking at the higher vessel normal operating temperature for the FHR (650C vs. 565C for MSBR) it would have to be about twice as thick as the MSBR vessel for a given inner diameter. Given the higher diameter, I'm calculating something like a 150 mm thick vessel to meet the 30 year life, and probably over 180 mm to get to the full 60 year service life. How is that supposed to be "thin walled"? It is just as thick as a BWR vessel.

The vessel is also humongously heavy. FLiBe being much heavier than water and there being a ridiculous amount of FLiBe in that vessel. Taking that into account, especially in terms of earthquake resistance, this would probably push the vessel thickness to over 200 mm to make it robust enough. Thicker than BWR vessels.

They are also talking about actively cooled flanges for the vessel. Again a serious risk in the event of loss of active cooling.

Then there is the DRACS thing which is an easy leak path for tritium, and an easy way to freeze up the entire decay heat removal path. A single ruptured tube in the DRACS, anywhere in the system, fully incapacitates the cooling system.

Then there is the fact that they are pushing for a 3400 MWt reactor for a reactor type where the biggest prototype ever built was 0 MWt - that is to say no prototypes ever (at least MSRs had the ARE and MSRE). And people barely got some tiny salt loops running. It seems like asking too much for any potential investor, so the concept risks getting stuck before it can get commercial.

Someone pinch me. How has this become the baseline design where DOE, CAS, natlabs, have all put their faith & money in?


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 Post subject: Re: New FHR whitepapers
PostPosted: Dec 15, 2013 10:00 pm 
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When I read these reports, the thing that struck me is that someone is (again) thinking that designing reactors is like making sausages.....


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 Post subject: Re: New FHR whitepapers
PostPosted: Dec 16, 2013 5:58 am 
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That appears to be more like a PB-AHTR.

The central station AHTR, 1500 MWe unit, has a very small aspect ratio.


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 Post subject: Re: New FHR whitepapers
PostPosted: Dec 19, 2013 12:34 am 
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Location: Berkeley, CA
I apologize that due to teaching and research, I've not been keeping up with the discussion forum the way I normally do.

Onrejch posted the link to the white papers that we published following a series of four expert workshops we hosted at UCB, UW Madison, and MIT in 2012, as a part of the 3-year DOE-NE Integrated Research Project we now have to develop the technical basis to design and license fluoride-salt cooled, high temperature reactors (FHRs). As many participants in this forum know, we've been working on technology to use fluoride salts as coolants for high-temperature, coated particle fuels, both in pebble and in plate forms. These reactors appear to have attractive attributes due to their intrinsically low operating pressures and the high average temperatures that they can deliver heat at (between 600 and 700°C with currently available structural materials).

Each white paper has an executive summary, and these should be interesting to review since they summarize some of the key issues that need to be addressed to utilize fluoride salts in high temperature reactors, ranging from methods to identify licensing basis events; to selection and experimental validation of codes for thermal hydraulics, neutronics, and structural mechanics; to issues for materials, fuels, and tritium and beryllium management.

In addition, there have been a series of efforts to develop various designs for AHTRs and FHRs, to explore the potential parameter space for this class of reactors. ORNL completed an important design study in 2012 examining a point design for a large, 3400 MWth AHTR.

Currently, as a part of our IRP work, UCB is developing a new design for a small, 236-MWth, Mk1 PB-FHR, that is coupled to a nuclear air combined cycle (NACC) using a GE 7FB gas turbine. We've been working with Lindsay Dempsey, who posts frequently to the forum and who has extensive expertise in gas turbine and power conversion technology, to establish the technical approach for high temperature reactors using fluoride salts to drive open air gas Brayton cycles. The baseline design is capable of producing 100 MWe of base load electricity (42% thermal efficiency), but to ramp up to 240-MWe with gas co-firing so it can also provide peaking power as well as other grid support services such as spinning reserve and frequency regulation.


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 Post subject: Re: New FHR whitepapers
PostPosted: Dec 25, 2013 1:57 am 
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Thank you Per for the update & details on your research.

Concerning Cyril R's questions about the large AHTR, here is the latest from ORNL: Fluoride Salt-Cooled High-Temperature Reactor Technology Development and Demonstration Roadmap, September 2013, ORNL/TM-2013/401. The vessel is discussed on pages 39 and 40.


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 Post subject: Re: New FHR whitepapers
PostPosted: Dec 25, 2013 3:02 am 
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ondrejch wrote:
Thank you Per for the update & details on your research.

Concerning Cyril R's questions about the large AHTR, here is the latest from ORNL: Fluoride Salt-Cooled High-Temperature Reactor Technology Development and Demonstration Roadmap, September 2013, ORNL/TM-2013/401. The vessel is discussed on pages 39 and 40.


Thank you, Ondrejch. This latest ORNL AHTR design provides the best developed approach to large, base load power output from FHRs. The full design report is available here, ORNL/TM-2012/320,

http://www.osti.gov/scitech/biblio/1054145


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 Post subject: Re: New FHR whitepapers
PostPosted: Dec 25, 2013 9:56 am 
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Cyril R wrote:
The large central station, 3400 MWt FHR appears to have become the baseline design for further focus.


I'll also point out that the SmAHTR concept http://info.ornl.gov/sites/publications/files/Pub26178.pdf is also alive and well with some limited on-going work this year. There are applications that demand both small and larger systems, so both scales are being considered.


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 Post subject: Re: New FHR whitepapers
PostPosted: Mar 13, 2014 12:23 am 
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ondrejch wrote:
http://fhr.nuc.berkeley.edu/?page_id=19

White Paper 1: FHR Subsystems Definition, Functional Requirement Definition, and Licensing Basis Event Identification
White Paper 2: FHR Methods and Experiments Program
White Paper 3: FHR Materials, Fuels and Components
White Paper 4: FHR Development Roadmap and Test Reactor Performance Requirements



I think it is good job to develop FHR in the future.


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 Post subject: Re: New FHR whitepapers
PostPosted: Mar 13, 2014 3:08 am 
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It is difficult to reply to the questions of IF and WHEN of the FHR without knowing WHERE.
If the place is Russia, India or China, the generation system from secondary coolant onwards can be fitted to a sodium cooled fast reactor.
In the proposed reactor, LiF component of the coolant requires a very high isotopic purity of 7Li due to presence of neutron poison 6Li in the natural lithium. This could hold up a trial prototype. The three countries mentioned above are building sodium cooled fast reactors and can easily test the secondary salt as a safety improvement in fast reactors.
With IFR non-proliferating reprocessing, the FHR could be a way to dispose off the LWR spent fuel if it is accepted. A higher percentage of TRU could provide the equivalent of 9% enrichment specified.


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 Post subject: Re: New FHR whitepapers
PostPosted: Mar 13, 2014 6:02 pm 
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The FHR seems to me a bridge to the MSR. It avoids some of the major challenges of the MSR as the complex fuel treatment and the issues with the fission product salts.

Perhaps the FHR might become an ideal design up to 2000MWe and the MSFR the ideal design for huge electricity generating power plants.


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 Post subject: Re: New FHR whitepapers
PostPosted: Mar 14, 2014 5:12 am 
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HolgerNarrog wrote:
The FHR seems to me a bridge to the MSR. It avoids some of the major challenges of the MSR as the complex fuel treatment and the issues with the fission product salts.

Perhaps the FHR might become an ideal design up to 2000MWe and the MSFR the ideal design for huge electricity generating power plants.


The FHR can be a technology bridge to the MSR, but the unique properties of the liquid fuel are lost. Realistically: what is the added value of a molten salt-cooled reactor over a lead-cooled reactor, which both use solid fuel ? Although a FHR can operate at higher temperature than a lead-cooled reactor(which operates between 400-480 degrees C), this brings also more challenges and requires more development.


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 Post subject: Re: New FHR whitepapers
PostPosted: Mar 15, 2014 3:58 am 
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camiel wrote:
The FHR can be a technology bridge to the MSR, but the unique properties of the liquid fuel are lost. Realistically: what is the added value of a molten salt-cooled reactor over a lead-cooled reactor, which both use solid fuel ? Although a FHR can operate at higher temperature than a lead-cooled reactor(which operates between 400-480 degrees C), this brings also more challenges and requires more development.

A salt cooled reactor is a bridge to salt handling technology. Either salt or lead as secondary coolant will reduce the fire risk from a sodium cooled fast reactor.
Reduction of moderator volume will make the reactor compact and reduce structural cost.


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 Post subject: Re: New FHR whitepapers
PostPosted: Mar 15, 2014 9:18 am 
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camiel wrote:
Realistically: what is the added value of a molten salt-cooled reactor over a lead-cooled reactor, which both use solid fuel?


The difference is the spectrum. Thermal spectrum can be seen as an added value.


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 Post subject: Re: New FHR whitepapers
PostPosted: Mar 16, 2014 3:02 am 
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Burghard wrote:
camiel wrote:
Realistically: what is the added value of a molten salt-cooled reactor over a lead-cooled reactor, which both use solid fuel?


The difference is the spectrum. Thermal spectrum can be seen as an added value.


Why choose, when you can have both? :mrgreen:

Competition is good, and its not as if we have only a few coal plants to displace...


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