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PostPosted: Dec 02, 2016 5:22 am 
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If anyone is interested in UK demand and supply options in 2050, I've co-authored a series of analysis:
http://euanmearns.com/uk-electricity-20 ... and-model/ outlines a "all electric scenario"
http://euanmearns.com/uk-electricity-20 ... ear-model/ outlines how this could be fulfilled with nuclear, based on a mix of PWRs and SMRs.
http://euanmearns.com/uk-electricity-pa ... and-solar/ outlines how wind and solar - with gas backup - could fulfil this

My co-author is a former nuclear engineer grounded in PWRs, so acted to curb my enthusiasm for MSRs in Part 2. It indicates the level of demand for advanced reactors though.

I wrote Part 3 with a "Requirements gathering" hat on. If we wanted to power the UK with wind and solar, what would it take?


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PostPosted: Dec 02, 2016 6:34 am 
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The thermal mass assumption is a very generous one if you assume heat pumps provide the primary heating output, given the awful state of the British housing (and other building) stock.
I came to the conclusion that peak electricity demand for heat pumps was something approaching 150GWe alone, based on an analysis by Robert Sansom at ICL.
I think this can be significantly peak-shaved using a mix of storage heaters and heat pumps, but I come to the conclusion that nuclear supply needs to be something in excess of 100GWe.
Which is surprisingly close to your figures.

With regards to energy storage - I recently stumbled across some BGS reports that make me believe several hundred gigawatt hours worth of heat could be economically stored in northern Kent (near Canterbury) using underground limestone caverns which could be finances partially by selling off the limestone for aggregates. I made a post about it in my "hot water pit storage" thread in the Energy Issues subforum.
I'm afraid I must disagree with you about the economics of turning an "MSR down or off" - the economics are even worse than they are with regards to a PWR. Even a PWR with its relatively high fueling cost saves virtually nothing from reducing power output in winter - its fueling outages must still occur when they were going to occur anyway, otherwise you risk pushing the fuel outage into the next winter (or not having enough fuel to make it to the summer if the year is colder than projected). It is likely that all you will achieve is discharge under-irradiated fuels.

With an MSR it probably reaches the point where it is cheaper to just heat resistor grids than throttle back - throttling back has all sorts of maintenance and wear and tear concerns, as you say. Even a CANDU is pretty much at that point. Either way it is probably more economic to simply sell electricity even more cheaply so you can get rid of it - at prices down to £1/MWh or less.

Also not sure about SMRs either - they tend to take the big problem of nuclear (large capital cost per kilowatt) and make it even worse - for some nebulous financing advantage that is moot anyway because no nuclear project is going to go forward without massive state support, any nuclear project gets crushed by CCGTs on capital cost otherwise. Likewise there is no serious chance that Hualong-1 or other pure-Chinese PWR designs will ever actually get built in the UK.

My own opinion is that based on industrial constraints [where will the 60+ pressure vessels come from for one thing] there are only two real routes open that can possibly keep pace with the rate of decarbonisation required to hit the targets (and fuel security etc etc etc).
1. Build EC6s as described in the CANMOX proposal, but keep building them - develop the programme along the lines of some sort of Darlington/CANDU 9 reactor with 640 tubes and 4 units per plant, then develop a CANDU coupled to a condensing carbon dioxide cycle to reduce capital costs and increase efficiency. That gives us minimum uranium input requirements without going for any crazy recycling cycles - with a design we could start building tommorow.

2. Try and ressurect the gas-graphite reactor programme, after all designing a new design from scratch for an 85GWe scheme is a negligible cost, and AGRs married with supercritical carbon dioxide cycles could be an interesting economic proposition. Would have to build LWRs as a stop gap however to get construction going, but it is feasible that it could be cheaper in the long run.

But that is just my two cents - we both know that none of these proposed scenarios will ever develop to anything close to reality.

EDIT:

District heating is £8,000 per dwelling according to DECC (or whatever it is called this week).
It just can't compete considering it creates a whole new maintenance requirement that would not exist in an all nuclear system.


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PostPosted: Dec 02, 2016 5:08 pm 
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^ Are you suggesting to use CO2 as a coolant in a modified EC6 to reduce the D2O requirements?


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PostPosted: Dec 02, 2016 6:14 pm 
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Titanium48 wrote:
^ Are you suggesting to use CO2 as a coolant in a modified EC6 to reduce the D2O requirements?


No, I am proposing a multiple reheat condensing carbon dioxide cycle be introduced in place of the existing secondary steam system. You would have big gas heater PCHEs in place of the current steam generator assemblies.
And an absolutely giant printed-circuit seawater-carbon dioxide condenser/gas cooler in place of the current large condenser assembly - you have to guarantee bottoming temperatures below 30 celsius for the cycle to work properly.

At 315 Celsius from an LWR they estimate ~38% - and even from the lower loop temperature of a CANDU 300 Celsius is likely obtainable given that we can build large PCHEs with almost ludicrous performance.
The previous estimate is only at 20MPa and we can push to 25MPa [or even the 30MPa of the turbines for the Allam cycle prototype] to gain back some of the efficiency loss - either way it should easily beat the ~33% of a normal CANDU station, with far more compact turbomachinery. And with winter water temperatures around the British islands ~40% is within reach.

EDIT: Here is a Sandia Report on the idea.
I think it might also be possible to use moderator heat in the cycle by dividing the LT Recuperator into an LT and IT Recuperator, then adding moderator water as a third cycle through the new LT Recuperator, this would allow the fraction of gas sent to the bypass compressor to be reduced which woudl reduce the total compressor power significantly.
However I have no tools available that would allow me to actually test that. And even if the effect is only a few megawatts it is heat that would go to waste otherwise and it does not seem to require significant additional plant. (The Recuperator would be replaced by two smaller recuperators and there would be an extra pump and pair of pipes, but that is about it).


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PostPosted: Dec 05, 2016 6:55 am 
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E Ireland wrote:
The thermal mass assumption is a very generous one if you assume heat pumps provide the primary heating output, given the awful state of the British housing (and other building) stock.


The heat loss was just an extrapolation of current trends - though admittedly it does get harder as the houses get a bit less awful.

If there is some form of workable "green deal" to encourage external insulation, then some of these old brick houses could have a huge heat capacity.

Quote:

With regards to energy storage - I recently stumbled across some BGS reports that make me believe several hundred gigawatt hours worth of heat could be economically stored in northern Kent (near Canterbury) using underground limestone caverns

Perhaps using Isentropic's technlogy?

I was thinking what would happen if instead of using "tanks" of gravel, they just used boreholes and heated / cooled 100m cubes.

(EDIT: Just read your post talking about limestone storage. Not at all the same)

Quote:
I'm afraid I must disagree with you about the economics of turning an "MSR down or off" - the economics are even worse than they are with regards to a PWR. Even a PWR with its relatively high fueling cost saves virtually nothing from reducing power output in winter - its fueling outages must still occur when they were going to occur anyway, otherwise you risk pushing the fuel outage into the next winter (or not having enough fuel to make it to the summer if the year is colder than projected). It is likely that all you will achieve is discharge under-irradiated fuels.


My thinking is - take the ThorCon design (same applies to Terrestrial). The core needs to be swapped out due to the neutron flux on the graphite. Basically a ThorCon core is good for 1 GW-year. Can't that be spread out over more than 4 years?

Ultimately though you want several "tiers" of energy, starting with what we call "base load" and ending with contingency reserve. The last one could be diesel power - what ever is cheapest to build - and might never get used.

There is discussion in Part 3 comments about the problems even diesels have if left idle for a long time - so some rotation might be needed.

Quote:
My own opinion is that based on industrial constraints [where will the 60+ pressure vessels come from for one thing] there are only two real routes open that can possibly keep pace with the rate of decarbonisation required to hit the targets (and fuel security etc etc etc).

Though the build out rate is much less than France achieved - though they now appear to have quality control problems with the pressure vessels.

But if Moltex or Terrestrial (or someone else) are successful, then industrial constraints are much easier. Especially with the offshore approach to land use.

Quote:
District heating is £8,000 per dwelling according to DECC (or whatever it is called this week).
It just can't compete considering it creates a whole new maintenance requirement that would not exist in an all nuclear system.


Interesting. Though a new boiler and fitting is about one third of that. £8K is not that unaffordable for "free" heat.

It would be cheaper in new build areas - except they need much less heat - so the payback will be even longer. It's probably something best retrofitted for "tight packed" suburbia.


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PostPosted: Dec 05, 2016 12:11 pm 
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alexterrell wrote:
Quote:

With regards to energy storage - I recently stumbled across some BGS reports that make me believe several hundred gigawatt hours worth of heat could be economically stored in northern Kent (near Canterbury) using underground limestone caverns

Perhaps using Isentropic's technlogy?

I was thinking what would happen if instead of using "tanks" of gravel, they just used boreholes and heated / cooled 100m cubes.

(EDIT: Just read your post talking about limestone storage. Not at all the same)

There are a lot of proposals for ways to inexpensively store very large amounts of heat energy (and thus regular energy) - the problem is that heating media is very expensive to obtain in the temperature range required. Even my proposal resorts to water but simply uses the limestone quarry galleries as very low cost pressure vessels.
I might try to run the calculations on using a terphenyl heat transfer oil like the one proposed for the CANDU-OCR in a salt cavern (which is the cheapest underground structure available but can't be used with pressurised water for obvious reasons).
alexterrell wrote:
Quote:
District heating is £8,000 per dwelling according to DECC (or whatever it is called this week).
It just can't compete considering it creates a whole new maintenance requirement that would not exist in an all nuclear system.


Interesting. Though a new boiler and fitting is about one third of that. £8K is not that unaffordable for "free" heat.

It would be cheaper in new build areas - except they need much less heat - so the payback will be even longer. It's probably something best retrofitted for "tight packed" suburbia.

Unfortunately whilst steam cycles can easily produce waste heat for these systems - moving to more efficient and economic power cycles makes it much more difficult.
I am sure if it is even possible to draw bleed-heat from a supercritical carbon dioxide system effeciently, let alone how you would actually achieve it.
Although a Pressure Tube reactor has the advantage that, if nothing else, you could draw the moderator water heat at District Heat temperatures, although moving it without having a very large delta-T might prove challenging.


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PostPosted: Dec 09, 2016 2:56 am 
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If you use a pressure tube reactor but are not restricted to natural uranium, you could have any or some of various advantages.
1. You could use a high boiling liquid like biphenyl as coolant while still using heavy water as the moderator and work at a lower pressure.
2. You could use a thorium-plutonium fuel and create U-233 fissile in the fuel and/or blanket.
3. Reduce the natural uranium use for same power.
4. Have a higher conversion ratio. It could go to a breeder.


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PostPosted: Dec 09, 2016 3:01 am 
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jagdish wrote:
If you use a pressure tube reactor but are not restricted to natural uranium, you could have any or some of various advantages.
1. You could use a high boiling liquid like biphenyl as coolant while still using heavy water as the moderator and work at a lower pressure.

Who said you can't run a CANDU-OCR on natural uranium?
Most of the research assumed NU because at the time enrichment was a rare thing in Canada [and it still is but less so as there is a practical source of enriched uranium now]

As demonstrated here, it is projected that a CANDU-OCR would be able to obtain burnups of at least 6125MWd/tU, and that was considered to be an extremely conservative estimate. They believed it could have been up to 15% more than that in reality - which makes it rather close to the CANDU 6's reference burnup thanks to the higher density UC fuel, larger reactor [less neutron leakage] and the thinner pressure tubes.


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PostPosted: Dec 09, 2016 8:46 pm 
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From what I've read, the UK uses about 160GW of equivalent power. Seems that nuclear could easily provide that power.

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