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Some nukes are better than others

Page history last edited by Andrew Alder 8 hours, 58 minutes ago

A page of energy issues


Some nukes are better than others. Here are some examples. It's not a complete list, but it should give some food for thought.


And some of these headings overlap. I know! But I hope it will prove informative even so.




The good



Many in operation.


Oxide fuel, either slightly enriched Uranium or MOX. Ordinary water cooling and moderation.


One serious accident, Three Mile Island, in which the melt didn't escape the pressure vessel. There was secondary containment, as in all modern PWRs, but it wasn't needed.


Safe. Can't be used to produce military material, see fool grade, and ideal candidate to support the NPT. Waste a solved problem.


Some recent PWR proposals are small and the proponents call them SMRs instead. Exactly how long this will fool the greenies is the question on everyone's lips, but it's worth a try and seems to be working well so far.



One prototype, EBR-2, operated and produced power for many years. The best fast reactor power station yet, and radically reduces the amount of fuel required and the amount of waste produced compared to a PWR. The best solution to the waste a PWR produces, in fact, as it can burn the leftover Uranium and Plutonium and other transuranics from spent PWR fuel, and these tend to be the longer-lived radionuclides in this waste, spectacularly so if you count the unused Uranium, 


Metallic fuel, a "starter" charge of enriched Uranium or other fissile material needed at first startup but from then on almost any fissile or fertile material can be used, notably spent PWR fuel as noted above. Sodium cooled, three levels (primary and secondary coolant and a unique fuel design providing a third level). No moderator, it's a fast reactor. 


Proliferation issues, yes, but relatively small compared to other fast reactors and to fusion plants. Ideal candidate to support the NPT


The bad


Proposed cladding failed. Not tested before significant commitment to the program. 


Originally planned to use natural Uranium fuel but in practice enrichment proved necessary owing to the cladding problem, which destroyed the economic case for building it.


Britain's second costliest mistake post-war, at least. The other candidate for first place is the Concorde.  



Unstable. That was publicly predicted by Western experts and acknowledged by the Soviets before it was built. See The upside of Chernobyl.


And yet, did you hear a single word of criticism of the design before it blew up? Where were the greenies? Oh, they had more important things to do, like chanting slogans outside PWRs and telling the public barefaced lies about Plutonium. See sex lies and nuclear power.


One serious accident of course, Chernobyl.


Ordinary light water cooling, graphite moderator, oxide fuel. Originally planned to use natural or even depleted Uranium fuel, such as spent PWR fuel. See why on earth did they build the RBMK.


Ten still operating as of 2020, the last to close in 2034, but with enriched fuel to remove the instability. But that also removes the economic justification, so all subsequent construction and the proposed successor the MKER cancelled.  


The ugly

 Many candidates. Some may yet prove to be ugly_ducklings. Others will remain ugly.



One of my pet peeves. Nuclear engineers love them. Two serious accidents, SL-1 and of course Fukushima.


No secondary coolant. The irradiated primary coolant goes through the turbines, as with the RBMK and SGHWR. This limits containment possibilities. See why on earth did they build the BWR.



Unsolved waste problems. Enormous in scale. Proliferation issues. Hyped. Proposed implementation always ten or more years in the future. My prediction is in the range AD 2200 to AD 3000.


The main problem is, it can't compete with PWRs and IFRs for a long, long time. It has all the same problems, but worse, and no redeeming features. apart from those in science fiction.


The various MSRs, SMRs etc

As with fusion, hyped. See the green nuclear backdown.


Possible exceptions are the little PWRs recently proposed, They are both PWR and SMR, and If they can combine the political cred of the SMR with the proven technology of the PWR it could work well.




There are two very different classes of reactor sometimes called MSR. 

  • Molten-Salt_Reactor_Experiment or MSRE used molten salt that contained the fuel, see also LFTR for other proposed designs.  MSRE got as far in 1965 as ITER hopes to by the end of the experiments that will start in 2035. So not the ugliest by a long way! 
  • Other designs use molten salt only as coolant, see molten_salt_reactor


Both have their advocates, but many of the advocates of the MSR do not even seem to know which of the two they are recommending, if they even know that there are two.



Even more various and popular than the MSR, and they have in common with the MSR that most advocates don't know what sort they mean. or if they do are careful not to say.


But that's the only ugly thing about small PWRs. They show promise. They are based on technology proven in naval propulsion and large power station PWRs. The only reason for not calling them PWRs is political. A week is a long time in politics, and the honeymoon with some greenies may not last when the time finally comes to build one. 




Magnox and UNGG

The UK and France both built dual-purpose plants, Magnox and UNGG respectively, to produce both weapons-grade Plutonium and electricity... not both at once, but either option depending how the plant was operated. Both had natural Uranium metal fuel, graphite moderator, and gas cooling. 


The UK later built larger Magnox reactors dedicated to electricity production. These were superseded by the unsuccessful AGR project. France went on instead to build a fleet of PWRs.


Some of the Brits now wish that they'd continued with more Magnox plants, but that horse has bolted. The latest British power reactor is a PWR.



Canada developed a unique and successful design using heavy water moderation and natural Uranium fuel as oxide, the CANDU. This was at least partly motivated by their heavy water expertise and capacity developed for the Manhattan Project. Uranium enrichment technology and capacity, on the other hand, was jealously kept under US control.


While designed primarily for natural Uranium, the excellent neutron economy allowed a wide variety of fuels to be used.


Development is continuing. But each successive generation looks more and more like a PWR. The latest CANDUs use light water cooling and heavy water moderation, unlike earlier designs that used heavy water for both. This reduces the heavy water inventory, a major cost, to about one-third of that required for earlier heavy water only designs. But this has also required slightly enriched Uranium fuel.



Heavy water moderated, light water cooled, water boiled in the core like in a BWR or RBMK. Able to use a variety of fuels, including natural Uranium, as oxide.


One built, in the UK, the Winfrith Reactor which successfully generated power for the grid from 1967 until 1990. A possible export order for Jervis_Bay_Nuclear_Power_Plant fell through when that project was cancelled, with South Africa also interested had that order gone ahead, but the design went no further.


Other Thorium reactors

India and China are spending significant amounts of money developing the Thorium (or more properly Thorium/Uranium or Th/U) fuel cycle. Thorium is more abundant than Uranium, and India in particular has lots of it. But there are several obstacles to rolling it out anytime soon. Here are just the two most obvious.


Firstly, the Th/U fuel cycle depends on the Uranium/Plutonium (or U/Pu) fuel cycle to get started. U-233 is created by irradiating natural Th-232 in a reactor. But that reactor needs fuel. The only natural fissile material is U-235, mined as Uranium of course. In order to "breed" U-233 from Thorium, you need a fuel for that reactor. Uranium and Plutonium are the only real possibilities. 


So India is for the moment concentrating on U/Pu to build up its inventory of fissile material (Plutonium in this case) with the declared intention of switching to Th/U as soon as possible.


Secondly, Th/U has a lot of catching up to do before it's a serious rival to U/Pu. The U/Pu fuel cycle, including but not only Uranium enrichment and Plutonium production, was developed for the Manhattan Project. The PWR was developed, based on this research and infrastructure, to power naval vessels. Military money paid for it all.


(But note that while this military research and infrastructure supported and influenced the nuclear power industry, it has never yet been the other way around. Yes, I say that a lot!)


And perhaps you can now see why the Manhattan Project did choose U/Pu and virtually ignored Th/U. It was simply that they were in a hurry.


Other Generation IV reactors

The phrase Generation IV reactor was coined by the founders of the Generation IV International Forum or GIF. The GIF promotes a disparate range of proposed designs, some of them already mentioned above, see  Generation_IV_reactor#Reactor_types.  





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