3 ms·

AFAIK one limitation is forging of the large pressure vessels, mainly the reactor itself and the steam generators. Those take a long time. Of course you can do

by jabl 8y ago

AFAIK one limitation is forging of the large pressure vessels, mainly the reactor itself and the steam generators. Those take a long time. Of course you can do multiple ones in parallel, but then the limit is that there's about 25 heavy forge presses on the planet, of which only a subset are doing nuclear work. So in total the capacity at the moment is maybe 50 large pressure vessels per year worldwide. If one plant requires one reactor and 4 steam generators that would then be 10 plants per year. Of course it's possible to increase the worldwide heavy forging capacity, but again, something that takes time. Then there are many reactor designs that don't use water as a coolant or moderator; those are obviously not restricted by heavy forge capacity. But those reactors are mostly on the drawing board and not available off the shelf.

ohyes 8y ago
The quality of the steel is the hard part of this. It is incredibly important to not have any defects in the pressure systems & turbine of a nuclear plant for obvious reasons.
mikemotherwell 8y ago
If Nuclear was committed to, would the number of these heavy forge presses likely go up, and costs come down? I have no idea, but it does seem that if there are bottlenecks in the process, demand for nuclear could bring costs come down dramatically. Am I missing something here?
- jbay808 8y ago
  Those heavy presses themselves seem to be nation-state level engineering projects, so it's unlikely that anyone would build more of them than they absolutely need. https://youtu.be/hpgK51w6uhk https://youtu.be/hpgK51w6uhk
- jabl 8y ago
  Oh, absolutely! Or well, maybe costs wouldn't come down that much, since AFAIK press forging is a pretty mature technology. I'm just saying a heavy press forge is a major infrastructure project on its own, and it won't just happen by snapping our fingers. It will take time. Then there's the question of whether it makes sense to embark on a major buildout of current style large light water reactors? If the market shifts towards smaller modular reactors (SMR's), then for light water SMR's smaller forges would likely do. Or further in the future non-water low pressure designs. My opinion is that given the urgency of addressing climate change, coal pollution etc., yes we should embark on a major buildout of currently available reactor types, while also massively increasing advanced reactor R&D&commercialization funding.
nnq 8y ago
Why would forging be a requirement? Hasn't material science reached a point where we can built alloys that can be just cast into the right shape? Can't the problem of them being slightly weaker be solved by just making them thicker (not a problem for nuclear I'd guess bc you don't build that many pieces and you don't need to move them much), or by just having stuff like turbines replaced more often? I know that mixing "nuclear" + "cheaper manufacturing" sounds scary, but maybe it's a better idea... why would you need "best of the best" materials for pieces that (1) stay in one place (they're not airplanes!) and (2) can be replaced/serviced/inspected on fixed schedules following fixed procedures on fixed budgets etc. Modern forges were perfected by the germans in the war because they wanted to build airplane parts (!!) and they wanter to build them fast... I'd imagine nuclear power technology has none of this requirements and can be re-designed to work with commodity low-quality parts and have the movable pieces easily replace-able... (I'd imagine that if people would get over the "uuh, nuclear, scarry, scarry" mindset nuclear technology could become a dirt cheap commodity and be build with a mixture of ceramics + cheap alloys just fine...)
- tcpekin 8y ago
  That's a pretty good question, so I looked things up a little. Casting, especially on pieces this big, is difficult. It has problems with chemical segregation due to temperature gradients in the material, as well as porosity from the differential shrinkage due to the same temperature gradients [1,2]. From [2] "Consolidation of porosity formed in the ingot during solidification and homogenization is the major aim of the initial stage of forging. After that, the material is forged to form the shape of the desired products." The porosity and chemical segregation if I remember correctly, is very bad in nuclear applications, where bubbling and embrittlement would only be accelerated in non-homogenous materials. They are usually 1 piece to minimize welds, and this is just a feeling, but I think replacing the pressure vessel is pretty much currently the same as buying a new reactor [4]. These are very radioactive 1000 ton pieces of solid metal that you need to move and dispose of. Interesting question though, and I'd want to look into it more later. [1] https://inis.iaea.org/collection/NCLCollectionStore/_Public/18/010/18010016.pdf https://inis.iaea.org/collection/NCLCollectionStore/_Public/... (pdf, p. 11) [2] https://www.sciencedirect.com/science/article/pii/B9781845699673500027?via%3Dihub https://www.sciencedirect.com/science/article/pii/B978184569... (can send a pdf if interested) [3] https://www.reddit.com/r/pics/comments/3mzltj/a_nuclear_reactor_being_forged/ https://www.reddit.com/r/pics/comments/3mzltj/a_nuclear_reac... [4] https://www.neimagazine.com/opinion/opinionreplace-the-rpv/ https://www.neimagazine.com/opinion/opinionreplace-the-rpv/

by jabl 8y ago

ohyes 8y ago

The quality of the steel is the hard part of this. It is incredibly important to not have any defects in the pressure systems & turbine of a nuclear plant for obvious reasons.

mikemotherwell 8y ago

If Nuclear was committed to, would the number of these heavy forge presses likely go up, and costs come down? I have no idea, but it does seem that if there are bottlenecks in the process, demand for nuclear could bring costs come down dramatically. Am I missing something here?

jbay808 8y ago
Those heavy presses themselves seem to be nation-state level engineering projects, so it's unlikely that anyone would build more of them than they absolutely need. https://youtu.be/hpgK51w6uhk https://youtu.be/hpgK51w6uhk
jabl 8y ago
Oh, absolutely! Or well, maybe costs wouldn't come down that much, since AFAIK press forging is a pretty mature technology. I'm just saying a heavy press forge is a major infrastructure project on its own, and it won't just happen by snapping our fingers. It will take time. Then there's the question of whether it makes sense to embark on a major buildout of current style large light water reactors? If the market shifts towards smaller modular reactors (SMR's), then for light water SMR's smaller forges would likely do. Or further in the future non-water low pressure designs. My opinion is that given the urgency of addressing climate change, coal pollution etc., yes we should embark on a major buildout of currently available reactor types, while also massively increasing advanced reactor R&D&commercialization funding.

nnq 8y ago

Why would forging be a requirement? Hasn't material science reached a point where we can built alloys that can be just cast into the right shape? Can't the problem of them being slightly weaker be solved by just making them thicker (not a problem for nuclear I'd guess bc you don't build that many pieces and you don't need to move them much), or by just having stuff like turbines replaced more often? I know that mixing "nuclear" + "cheaper manufacturing" sounds scary, but maybe it's a better idea... why would you need "best of the best" materials for pieces that (1) stay in one place (they're not airplanes!) and (2) can be replaced/serviced/inspected on fixed schedules following fixed procedures on fixed budgets etc. Modern forges were perfected by the germans in the war because they wanted to build airplane parts (!!) and they wanter to build them fast... I'd imagine nuclear power technology has none of this requirements and can be re-designed to work with commodity low-quality parts and have the movable pieces easily replace-able... (I'd imagine that if people would get over the "uuh, nuclear, scarry, scarry" mindset nuclear technology could become a dirt cheap commodity and be build with a mixture of ceramics + cheap alloys just fine...)

tcpekin 8y ago
That's a pretty good question, so I looked things up a little. Casting, especially on pieces this big, is difficult. It has problems with chemical segregation due to temperature gradients in the material, as well as porosity from the differential shrinkage due to the same temperature gradients [1,2]. From [2] "Consolidation of porosity formed in the ingot during solidification and homogenization is the major aim of the initial stage of forging. After that, the material is forged to form the shape of the desired products." The porosity and chemical segregation if I remember correctly, is very bad in nuclear applications, where bubbling and embrittlement would only be accelerated in non-homogenous materials. They are usually 1 piece to minimize welds, and this is just a feeling, but I think replacing the pressure vessel is pretty much currently the same as buying a new reactor [4]. These are very radioactive 1000 ton pieces of solid metal that you need to move and dispose of. Interesting question though, and I'd want to look into it more later. [1] https://inis.iaea.org/collection/NCLCollectionStore/_Public/18/010/18010016.pdf https://inis.iaea.org/collection/NCLCollectionStore/_Public/... (pdf, p. 11) [2] https://www.sciencedirect.com/science/article/pii/B9781845699673500027?via%3Dihub https://www.sciencedirect.com/science/article/pii/B978184569... (can send a pdf if interested) [3] https://www.reddit.com/r/pics/comments/3mzltj/a_nuclear_reactor_being_forged/ https://www.reddit.com/r/pics/comments/3mzltj/a_nuclear_reac... [4] https://www.neimagazine.com/opinion/opinionreplace-the-rpv/ https://www.neimagazine.com/opinion/opinionreplace-the-rpv/