AHC/WI: Large Commonwealth Civilian Nuclear Program

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I came across something interesting on liquid cooled organically moderated and cooled reactors too. It's only liquid cooled, not gas, but it does involve a Commonwealth member.

The United States Atomic Energy Commission built an organically cooled and moderated reactor, Piqua, which was decommissioned after only three years due to coolant decomposition and fouling that caused some control rods to become stuck.

In contrast, the Canadian WR-1 heavy water moderated organically cooled reactor operated successfully for twenty years. The initial plan was to start the reactor with light coolant, heat things up, and the load heavier coolant, but the light coolant decomposed slowly enough that the switch was never made. The reactor was successful enough that Ontario Hydro also considered switching from heavy water cooled CANDU reactors to organically cooled CANDU reactors, which were estimated to be 10% less expensive to build and operate. Ontario Hydro stuck with heavy water CANDU reactors to simplify training and logistics, but apparently India is now considering a similar reactor design.
 
Gas cooled reactors can use Rankine cycle steam turbines from coal fired power plants, but why do that when they can directly drive Brayton cycle gas turbines from natural gas power plants? By the 1990s Brayton cycle turbines were seeing service in natural gas power plants.
The Rankine cycle turbines were well understood. Set up the steam generators right, and there's almost no development needed on them. Even the steam generators are a fairly low-risk technology.

The big Brayton cycle turbines you'd need would have relatively little in common with gas turbines, since the working fluid has changed from air to helium and the combustion chamber replaced with a nuclear reactor. The cycle has promise, but is probably another another development generation.
 

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The Rankine cycle turbines were well understood. Set up the steam generators right, and there's almost no development needed on them. Even the steam generators are a fairly low-risk technology.

The big Brayton cycle turbines you'd need would have relatively little in common with gas turbines, since the working fluid has changed from air to helium and the combustion chamber replaced with a nuclear reactor. The cycle has promise, but is probably another another development generation.

There were some powerplants built using closed cycle gas turbines in the 1960s and 1970s. It was tested on the ML-1 nuclear reactor of the United States Army Nuclear Power Program, but closed cycle gas turbines were mostly used in coal power plants. Notably, ML-1 also used nitrogen gas.

There was also the Soviet Tupolev Tu-155 (a Tupolev Tu-154 variant) in the 1980s. It used hydrogen powered jet engines, which are open cycle Brayton gas turbines. That's probably more difficult than adapting the Brayton cycle for a prototype nuclear power station.
 
You don't use helium to go to 400 °C. It's very high temperature reactor coolant for conditions twice as hot. I'm not sure the expense of better coolants could be justified at only 400 °C, since carbon dioxide's worst effects only start above that temperature. You can't use Magnox type cladding above 400 °C either. It would be such a new design that it wouldn't even be a natural evolution like a Super Magnox.

Except that He has got better heat transfer capacities than CO2 so you would have a smaller core for the same output.

We're talking theoretical deisgn here though.

I thought it was peaceful nuclear explosions and then later it became water cooled designs?
Not according to this document among other things. See page 4.
A Magnox reactor produces better steam than a LWRs so these kind of proposals make perfect sense.

Coal uses Rankine cycle steam turbines. With a Brayton cycle gas turbine reactor it would make more sense to use a natural gas turbine.

Having fully interchangeable steam turbines between fossil and nuclear stations is a big cost saving and operational advantage.
The steam turbines for LWRs are rather complex pieces of machinery because of the fact that quality of the steam produce in a LWR is so low.

I would like to keep closed Brayton cycle stuff out of this. The reason why? Brayton cycle power conversion has been proposed for nuclear reactors since the late 1940s! Yet has any reactor or prototype been built with this power conversion technology? None at all so far.
Brayton cycle power conversion will be a big engineering step to take. It will be costly and issues will emerge during development. Sure it would be great if the UK could get there first. But lets focus on steam cycles first.

I don't see how having moderating cladding would be an advantage.
Its all about improving the neutron economy. Instead of losing neutrons to the steel cladding you keep them with a beryllium cladding and get a bit of moderation as well.

What kinds of things would the Super Magnox have involved?
As I've said information on this is very scarce.

Online refueling was optional? Sure it never quite worked as planned, but the economic case for AGR was based around online refueling.
Its far more complicated than this. Why don't you spend some time this week-end having a look at this document in Kew Gardens?
The file is super thick and there's all kind of interesting stuff there. The BWR tender for example and very different designs of AGR too. Some of which are refuelled off-load.

I don't know how the gas flow and fuel element design could be left undecided at that point, seeing as that's a major part of nuclear reactor design.
Try to compare the prototype Windscale AGR and Dungess B and the differences are vast including:
-Fuel element design
-Pressure vessel design
-Gas circuit design

It is because the prototype was so different from what was built/tendered that Dungeness B and the other AGRs had so many issues. You can't upscale from 100MWt to 1500MWt without running into issues.

Carbon dioxide corrodes graphite too?
You have no idea what kind of soup the gas circuit of an AGR is. Its unbelievable at first what's in there besides 99% of CO2.
Yes the CO2 and graphite do react with each other. The CO2 "eats" the graphite basically. The process can be controlled to a degree. But if you increase gas pressure and power density further on an AGR, you need a replaceable moderator. The idea was studied in the 1980s.

By the 1990s Brayton cycle turbines were seeing service in natural gas power plants.

Open Brayton cycle turbines, based on combustion chambers. They're just like jet engines basically. Closed cycle Brayton cycle turbines on the other hand are something else that's completely different. You would need closed cycle Brayton turbines for power conversion from a nuclear reactor.
 

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What was the United Kingdom doing with breeder reactors prior to PRISM?

Did Canada ever look into breeder reactor technology, or was that not much of a concern given Canada's nuclear self-sufficiency?
 
What was the United Kingdom doing with breeder reactors prior to PRISM?
Nothing much, just a 14 MWe technology demonstrator brought online in 1959 and a 250 MWe prototype brought online in 1975.
DounreayJM.jpg
 

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Nothing much, just a 14 MWe technology demonstrator brought online in 1959 and a 250 MWe prototype brought online in 1975.
DounreayJM.jpg

What about MOX fuel research? The United Kingdom has the world's largest stockpile of civillian plutonium, and that could have been an interesting route to pursue. It would have been possible to greatly reduce or even eliminate the need for enrichment facilities for the AGR and water cooled reactors if MOX fuel was used.
 
What about MOX fuel research? The United Kingdom has the world's largest stockpile of civillian plutonium, and that could have been an interesting route to pursue. It would have been possible to greatly reduce or even eliminate the need for enrichment facilities for the AGR and water cooled reactors if MOX fuel was used.
About 20 tonnes of MOX fuel was produced to support the fast reactor programme; when that was terminated, work began on MOX fuel for thermal reactors primarily for export. A pilot plant opened in 1993, and the production-scale plant was completed in 1997, partly justified by the need to do something with the plutonium stockpile. When completed it represented about 40% of the world's MOX production capacity. It didn't work very well - it didn't start operating until 2001, produced less than 1% of design output in the first five years, and was shut down in 2011 having made a £2.2 billion loss.
 

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About 20 tonnes of MOX fuel was produced to support the fast reactor programme; when that was terminated, work began on MOX fuel for thermal reactors primarily for export. A pilot plant opened in 1993, and the production-scale plant was completed in 1997, partly justified by the need to do something with the plutonium stockpile. When completed it represented about 40% of the world's MOX production capacity. It didn't work very well - it didn't start operating until 2001, produced less than 1% of design output in the first five years, and was shut down in 2011 having made a £2.2 billion loss.

The United States had more success with MOX despite a total lack of civillian reprocessing infrastructure. How did the United Kingdom have such issues given that MOX fabrication is an additional step to the reprocessing it has already been doing since the 1950s?
 
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