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PostPosted: Jun 12, 2009 1:34 pm 
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STG wrote:
However, knowing Italy a little, even the return to nuclear power is questionable...


Even if I tend to agree with you that a nuclear comeback in Italy is very unlikely, I'm not sure why you claim it's not feasible at all to build HWRs in the EU, the last nuclear plants build in Romania (an Ansaldo and Aecl cooperation) are indeed Candus (Candu-6); for Italy, in the near term, I' d see very favourably the development of Candu-9, for example in a configuration similar to the Darlington site in Canada, i.e. 4 reactors of 880 MWe each (for example, in ten different sites across the country, about 35 GWe and a potential 280 TWh/year in total vs 340 TWh/year today needed, of which about 60 TWh/year is from renewable). It's a simple, efficient and modular and quite economic strategy, in particular because it phases out costly natural gas for electricity genearation (the cost of NG in Italy is > 350 euros per 1000 mc); moreover, doesn't need very high heavy industries infrastructure

Obviously, in the long term (20 or 30 years and more) there are a lot of other strategies to adopt, including MSRs (I'm very sceptical about ADS Rubbia's idea, instead), particurally if they allow the exploitation of low temperature waste heat, district heating in primis (in the colder North), but also desalination in the southern regions, for example in costal sites as Kirk envisaged


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PostPosted: Jun 12, 2009 2:22 pm 
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Doesn't Romania already had CANDU reactors? This would make the licensing process a lot easier...Now you have to start from scratch for Italy, and they're most likely going to look to a country which employs many Italians....

Exploitation of LLW or HLW for heat is crazy...Have you any idea about the costs? Furthermore I would really advise it not to do that in Italy. Italians already have problems dealing with normal waste...The use of waste for heating is just fiction, it will never be allowed

And you might be a sceptic about ADS...This doesn't prevent Rubbia being a Nobel prize winner with a lot of respect in Italy, which will most probably be part of scientific comittees. Furthermore the ADS design isn't that crazy, it has some specific advantages...

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PostPosted: Jun 12, 2009 2:56 pm 
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The MSBR plans included exploiting the FP decay heat as part of the reactor output.
Since we pull out the Xe and this puts off a lot of heat (5% by some estimates - haven't made my own yet but perhaps soon) this is not a trivial amount.
I would also think that we do not have some of the constraints for the heat exchanger that the primary heat exchanger does.

The primary HX is constrained by the need to minimize the volume of the fuel salt.

An off-gas to secondary coolant HX would not have such a requirement.
This should allow a smaller delta T between the heat source (Xe gas in this case) and the secondary salt.

I am thinking we can use this to inject the remaining 5% power into the secondary salt at the high temperature end of the secondary salt.


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PostPosted: Jun 12, 2009 3:26 pm 
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STG wrote:
Doesn't Romania already had CANDU reactors? This would make the licensing process a lot easier...Now you have to start from scratch for Italy, and they're most likely going to look to a country which employs many Italians....

Exploitation of LLW or HLW for heat is crazy...Have you any idea about the costs? Furthermore I would really advise it not to do that in Italy. Italians already have problems dealing with normal waste...The use of waste for heating is just fiction, it will never be allowed

And you might be a sceptic about ADS...This doesn't prevent Rubbia being a Nobel prize winner with a lot of respect in Italy, which will most probably be part of scientific comittees. Furthermore the ADS design isn't that crazy, it has some specific advantages...


I can' t say about lobbing or PR, of course, ADS may have a lot of advantages, but there are many different strategies, including MSRs, which can do the same with much less complexity and infrastructures, thus costs - moreover, I don' t see on it any safety improvement, they can avoid intrinsically criticality accidents, but not a loss of coolant accident, in that case ADS is only vaporwave, in my opinion

I didn't mean exploiting heat from nuclear spent fuel :?: , but from waste heat using nuclear plants in cogeneration, there are a couple of examples of it in Europe (Cernavoda in Romania and Refuna in Swiss conf), even using current LWR and HWR technology, with an high temperature nuclear technology like LFTR is likely even easier. Anyway, no use of nuclear wastes for heating :P (there is furthermore little heat in them...)


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PostPosted: Jun 22, 2009 1:09 am 
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ondrejch wrote:
However, there is no shortage of Gazprom sellouts in Europe neither, which seems to be the real obstacle.

Have any Italian politicians been exposed as Gazprom stooges? There's a blogger I read who I expect would be interested to know...


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PostPosted: Jun 22, 2009 1:57 am 
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Lars wrote:
I am thinking we can use this to inject the remaining 5% power into the secondary salt at the high temperature end of the secondary salt.


Suppose we have a perfect Carnot engine with 2 GW(th) input at 800 K, and an output at 400 K. (These numbers are clearly rounded to make the math more obvious.) The efficiency will be 50%, so that we have 1 GW(mechanical) output and 1 GW(th) output.

Now suppose we add 100 MW(th) at the input, by raising the absolute input temperature to 820 K (assume heat capacity is constant over temperature), while keeping the output temperature at 400 K.

The Carnot efficiency is now 52.5%, and the outputs are 1.076 GW(mechanical) and 1.024 GW(th).

In other words, our efficiency of converting energy added at the margin by raising the temperature of the stream is 76%. Pretty good!

-Iain


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PostPosted: Jun 22, 2009 11:36 pm 
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Alex P wrote:
STG wrote:
However, knowing Italy a little, even the return to nuclear power is questionable...


Even if I tend to agree with you that a nuclear comeback in Italy is very unlikely, I'm not sure why you claim it's not feasible at all to build HWRs in the EU, the last nuclear plants build in Romania (an Ansaldo and Aecl cooperation) are indeed Candus (Candu-6); for Italy, in the near term, I' d see very favourably the development of Candu-9, for example in a configuration similar to the Darlington site in Canada, i.e. 4 reactors of 880 MWe each (for example, in ten different sites across the country, about 35 GWe and a potential 280 TWh/year in total vs 340 TWh/year today needed, of which about 60 TWh/year is from renewable). It's a simple, efficient and modular and quite economic strategy, in particular because it phases out costly natural gas for electricity genearation (the cost of NG in Italy is > 350 euros per 1000 mc); moreover, doesn't need very high heavy industries infrastructure

Obviously, in the long term (20 or 30 years and more) there are a lot of other strategies to adopt, including MSRs (I'm very sceptical about ADS Rubbia's idea, instead), particurally if they allow the exploitation of low temperature waste heat, district heating in primis (in the colder North), but also desalination in the southern regions, for example in costal sites as Kirk envisaged

Italy has a lot of SNF being reprocessed. Recovered uranium can be used as fuel in Candu.


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PostPosted: Jul 28, 2009 6:46 pm 
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Italy is cutting deals left and right with nuclear suppliers. Why anyone doesn't take this seriously is beyond me. They will start with 1000MW plus reactors of course..they have a huge industrial load. Italy is not Ghana for goodness sakes. At the very minimum, they need plants to they can stop buying oil from Libya and Algeria.

David

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PostPosted: Jul 29, 2009 8:13 am 
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Alex P wrote:
I didn't mean exploiting heat from nuclear spent fuel :?: , but from waste heat using nuclear plants in cogeneration, there are a couple of examples of it in Europe

It is a subject I have always wondered about. Co-generation is perfectly good but why spurn the heat from spent fuel?
If we can somehow leach the freshly removed spent fuel with water, the highly radioactive cesium137 and strontium90 isotopes shall go into solution. They are potentially as good as Pu238 for nuclear batteries. I think we can burn the Zr cladding in chlorine gas and wet grind the remainder in water by remote control to extract the required isotopes.


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PostPosted: Jul 29, 2009 9:52 am 
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The process you describe sounds like it generates a significant amount of solvents that have become contaminated with radioactive material.
Is this right?


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PostPosted: Jul 29, 2009 12:47 pm 
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jagdish wrote:
It is a subject I have always wondered about. Co-generation is perfectly good but why spurn the heat from spent fuel?
If we can somehow leach the freshly removed spent fuel with water, the highly radioactive cesium137 and strontium90 isotopes shall go into solution. They are potentially as good as Pu238 for nuclear batteries. I think we can burn the Zr cladding in chlorine gas and wet grind the remainder in water by remote control to extract the required isotopes.


The Chinese have some pilot system running that scavenges heat from the spent fuel pool to supply a small district heating loop. How large and how effective I don't know.


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PostPosted: Jul 29, 2009 2:11 pm 
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If the heat from the spent fuel stored at site is converted to electricity, it could provide assured power for operation and safety of the plant. Diesel generators kept for the purpose can be retired after spent fuel is put into use!!


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PostPosted: Jul 29, 2009 2:32 pm 
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DV82XL wrote:
The Chinese have some pilot system running that scavenges heat from the spent fuel pool to supply a small district heating loop. How large and how effective I don't know.


A follow-up: The plant was going to be built at Yingkou in Liaoning province however the idea was scrapped when it was decided to expand Hongyanhe nuclear power station with LWRs.


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PostPosted: Jul 29, 2009 5:44 pm 
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jagdish wrote:
If the heat from the spent fuel stored at site is converted to electricity, it could provide assured power for operation and safety of the plant. Diesel generators kept for the purpose can be retired after spent fuel is put into use!!


The heat quality from the spent fuel pool can not be used because of it's low quality (low temperature heat). It could for instance be used only to supply some heating for fish farming. Letting the fuel heat up more would also be very very irresponsible. That fuel has been in the reactor and had to be unloaded because it has reached its limits, the fuel is afterwords put to rest to make sure it fulfills its main duty: dispersion barrier for fission products!

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PostPosted: Jul 29, 2009 6:39 pm 
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STG wrote:
Letting the fuel heat up more would also be very very irresponsible. That fuel has been in the reactor and had to be unloaded because it has reached its limits,
....as we found out last year at Hungary's Paksi NPP, when SNF was improperly stored, causing a batch of assemblies in the pool to boil water, dry out partially, and fail the cladding, releasing fission products....
STG wrote:
the fuel is afterwords put to rest to make sure it fulfills its main duty: dispersion barrier for fission products!
Thanks for pointing out what many here seem to be ignoring : fission products are way too hot to store in purified (extracted) form.
They need to be dispersed in some sort of matrix material.
In the case of LFTRs, that default material should probably be ThF4 -- just as in LWRs its UO2.


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