Post by Roger Clifton on Jun 11, 2013 13:15:31 GMT 9.5
The Bush administration led the GNEP which offered to spread fast reactors around the world, however the Obama admin did not fund it. Instead it has provided 450 M$ in two rounds to accelerate the licensing of small, mass-production reactors. Readiness for market implied the more conservative, slow-neutron designs.
mPower was announced as the winner of the first round. Full story posted 20121121
The second round is also about acceleration: US DoE "solicit proposals for projects that have the potential to be licensed by the Nuclear Regulatory Commission and achieve commercial operation around 2025". More posted20130313.
For those of us concerned about reliable power supplies in a future angry climate, an attraction is that the mPower's condensor is air-cooled, so it can be located away from the sea. Away from a rising, stormy sea, and its crowded, fearful, coastal population.
Conservative design choice allowed the Liberty Ships program to mass-produce very cheap, sturdy ships during WWII. The mobilisation was made possible by an international perception of crisis.
I am not convinced that SMRs a reasonable solution to grid energy production. They are just too small, I understand the argument that the existing large designs require too many large forgings which we don't have the capacity for at the moment, but we would apparently be able to spit out reactors in the 500-900MWe range relatively easily (see the SBWR).
Post by anonposter on Jun 12, 2013 5:46:23 GMT 9.5
SMRs as I see it are a reasonable solution to small grid energy production (i.e. the places that can't support a 1 GW unit) as well as for remote power (the mPower is probably a bit big for remote needs, probably the right size for SA though).
Post by anonposter on Jun 12, 2013 9:14:38 GMT 9.5
The remote needs I was thinking of would be islands. Niche market for sure, but in a way that's an advantage as the fossil fuel industry won't lose much if we got it (so not as much motivation to fund opposition to them).
Post by David B. Benson on Jun 12, 2013 14:19:44 GMT 9.5
Transatomic Power's WAMSR reactors turn high-level nuclear waste into electric power. transatomicpower.com/products.php Our compact 500 MWe molten salt reactor can be manufactured economically at a central location and transported by rail to the reactor site. That is a very impressive claim indeed.
The US Department of Energy has just authorized funding for a second SMR-- NuScale. According to an article in NEI Nuclear Notes:
"[NuScale offers] a smaller, scalable version of pressurized water reactor technology with natural safety features which enable it to safely shut down and self-cool, with no operator action, no AC or DC power, and no external water. Each NuScale Power Module is 45 MW and has a fully integrated, factory-built containment and reactor vessel."
Post by Roger Clifton on May 3, 2014 17:44:18 GMT 9.5
DBB says the development of the mPower SMR has faltered.
At 180 MW and ~5 $/W the mPower would still be a billion-dollar gamble for any financier. The concept of "small, modular and mass produced" implied in the SMR Initiative is better served by the remaining contender, the Nuscale reactor of 45 MW. Presumably the ballpark 200 M$ cost would be easier to find for a utility that wants to start small and prove the concept before ordering a series of the same reactor.
The US DoE is administering the SMR Initiative on the basis of making SMRs commercially viable in the current world market. The same initiative could have been driven by a more heroic vision of the US saving the Greenhouse for the world. However we have a long way to go before world opinion has the necessary sense of crisis.
Post by Roger Clifton on May 11, 2014 18:52:48 GMT 9.5
The NuScale design (see) has a long thin reactor vessel (containing core and steam generator) inside a long thin containment vessel, immersed in a below-ground pool. The stretch allows gravity to circulate the coolant without pumps.
A curiosity about the NuScale is that the cavity between the reactor pressure vessel and the containment vessel acts as a vacuum flask. Throughout the life of the reactor, vacuum pumps act to maintain thermal isolation. In the process they ensure that hydrogen leakage during any hypothetical incident would be removed before contacting oxygen.
I guess that the reactor pressure vessel wall will be at a temperature of at least 100° C, so there will be a certain amount of heat radiating across the vacuum gap, conducting through the containment wall into the pool. Somewhere in the design they would have to cool the pool water to a temperature to be tolerated by the pool wall and host rock beyond for 60 years.
Post by David B. Benson on May 16, 2014 10:29:48 GMT 9.5
Going that deep the ground temperature is a constant 10 degrees Celsius. I strongly suspect that an excess simply spreads away. More of a concern is evaporative loss of the pool water. Some modest makeup is required.
Post by Roger Clifton on May 18, 2014 17:32:38 GMT 9.5
Referring to the pool in which the NuScale reactor would be immersed, I worried that the water would need to be cooled, lest it eventually boil. DBB says that heat would likely conduct away, but the pool would still need make-up water. (However I reckon even 1% of ~200 MW thermal would need removal.) Assurance of passive cooling of fission products on shutdown would also require make-up water to flow in as the pool water evaporated.
Yes, I guess it could be built below the water table too, so that a hypothetical breach of the pool would not lose water. However the idea of having a long-lived pool near boiling temperature seems to be asking for trouble for the longevity of the (concrete?) pool wall, and the rock immediately beyond. If any hydraulic connectivity developed outside the wall across the 60 years, a convection system would be set up, potentially dissolving the rock, infill, grout or concrete. Metal corrosion could be that much more active too, with steel in two different temperature zones acting as dissimilar metals in an electrochemical cell.
Would the robots be happy to work at that temperature? Inspections have to be carried out, and presumably some maintenance functions such as cleaning would be performed by robots.
As I understand it, in normal operation essentially all the heat is removed via the steam generator. The containment vessel will remain close to 10 degrees Celcius as the actual heat lost via IR radiation from the reactor pressure vessel must be quite small while the outer pool is substantial, enough for emergency cooling if required. Nonetheless, the pool water will evaporate in normal operation so some small makeup is necessary. As for the outer pool wall remaining without leaks for 60 years, while I leave that to the civil engineers, I've talked to the local CE professors enough to have no doubts about the ability to do so. Some minor repairs might be be required due to (small) ground movements. If so, I assume the reactors are shut down for the short time required to drain the pool, repair and refill.
Indian 220MW PHWR is the most economical option of SMR for a country starting afresh like Australia, Namibia or even Kazakhstan. A number are already in use. That is, if politics permits. Canada is an alternate fuel source. New SMR designs may or may not be ever developed.
AP1000s are not easily mass produced because they require massive forgings. It is the SMRs, the small modular reactors, that are designed so they can be mass produced under licence in any industrialised country.
"[AP1000s] require massive forgings". Are you talking about the 6 inch thick single mould required for the Shell Flanges for Reactor Pressure Vessels?
OK, thanks for the heads up. These things designed for 70 atmospheres up are not so easy to mass produce. SMR's at one atmosphere are! Good stuff.
Large forgings are needed for designs like big PWRs and BWRs that enclose their core inside their pressure vessel. The head on the RPV may amass more than 200 tonnes and take years to deliver.
Heavy forgings are not so needed by large reactors whose cores run at near-atmospheric pressures. These are metal-cooled or salt-cooled and can be quite big. The EBR2 (IFR) for example, was cooled by sodium and evolved into PRISM, of output 300 MWe. I doubt if PRISM's design is ready for mass production.
However the SMRs are specifically designed to be modular, enabling factory production and potentially mass production. NuScale is a PWR, a small one at 50 MWe, being accelerated through licensing by US DoE. The recent declaration by President Obama that the US is shifting to low carbon power increases the likelihood of a sufficiently large market for the NuScale to get into production, perhaps eventually mass production.