CANDU fuel cycles - so many, but we only use one, why?

OVERKILL

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I know I've posted about the flexible nature of the CANDU reactor in the past. Not sure if my American friends on here are aware, but the US actually briefly pursued (and constructed) a heavy water reactor too, but it never amounted to anything.

PHWR reactors have the relatively unique characteristic of being extremely flexible with what fuels them, this is due to the much better neutron economy as the result of the deuterium moderator. It requires much lower levels of fissile material in order to sustain a chain reaction, which is why natural uranium can be used as fuel, requiring no enrichment.

Of course, if you can use natural uranium, that means you can use anything else that provides a similar fissile equivalence, this includes:
- Depleted uranium
- Spent PWR/BWR fuel
- Thorium blended with plutonium or LEU

SNC Lavalin, the company that bought CANDU energy from Atomic Energy Canada Limited produced the following advert for the AFCR CANDU, which is just a slight evolutionary "tweak" of the mature Enhanced CANDU 6, itself a tweak of a design that has been around since the 1970's, but had been evolved into a Gen3/Gen3+ design; kept current.

Screen Shot 2021-10-02 at 3.24.24 PM.png


Which sounds novel, until you look back to historic AECL CANDU vision documents:
AECLs-fuel-cycle-vision-for-CANDU-2.jpg


Because alternative fuel cycles for the CANDU had been a part of its development all along. They were just never pursued because the market didn't exist.

Put a different way, all existing CANDU reactors are technically capable of running on these alternative fuel cycles, but this has never been advertised as a feature until the AFCR, as part of its development, which happened using the C6's at Qinshan, was for the use of used LWR fuel, and that created the foundation for the "flexible" moniker/designation even though it's basically just a C6 with a few tweaks.

China is the only place in the world currently leveraging an alternative fuel cycle with a CANDU. The rest of them are using the traditional NU fuel bundle design, even India, which has substantial thorium reserves. The reason is that the uranium supply chain and fuel cycle is already well established, which makes it cheap. If uranium were to become more scarce, I suspect we'd see a renewed interest in not only alternative fuel cycles, but also reprocessing.

While there's a ton of interest, presently, in some very revolutionary reactor designs, this also brings with it significant risk. There have been hundreds if not thousands of paper reactors designed over the years that were not pursued or abandoned for reasons that killed their commercial viability. Water has proven to be the most successful moderator, even though it is not the only one to reach commercial success. The UK has had mixed results with graphite, as have the Soviets/Russians. Therefore, it should surprise nobody then that a "modern" spin on traditional designs has become a thing with respect to the latest SMR craze. GE Hitachi are now offering a BWR SMR and SNC has revived the old CANDU 3 design and are now pitching it as an SMR. Both based on mature reactor designs and thus no impediments to their viability and construction.

Contrarily, MSR (molten salt) reactors have some significant hurdles to overcome, one of which being the inherently corrosive nature of the salts, which has proven to be a significant problem with selection of materials and durability of not only the vessels themselves, but pumps and other components. This is why they were never pursued beyond testing back in the 1960's.

Since the C3 is just a scaled-down C6, it has the same potential for flexible fuelling, whether anyone adopts it and uses it however, is another thing entirely.

The next 10-20 years will be an interesting time for the nuclear industry, there's a ton of new technology, something we haven't seen since the 1960's before the PWR and BWR took hold and became the dominant designs. Whether that will translate into an actual uptake of alternative fuel cycle designs will be something to watch. For the US, being able to use their existing waste stores as fuel should have appeal, but there has been no interest in reactors that can actually do that, like the CANDU, thus far. Even PUREX reprocessing, which is tried and true and used extensively in Europe hasn't been pursued. So, if there are alternative fuel cycle reactors built, I suspect they will be the result of private capital invested by folks like Gates.

It all comes back to the established and optimized supply chain. Conceivably a MOX and/or RU or NUE fuel cycle agreement could be negotiated between Ontario and the US, but that's never come to be either, even though the viability of such an arrangement has already been explored. There are all kinds of possibilities, it seems that, for the time being, that status quo has some tremendous staying power, so I'm hesitantly optimistic to see what the future brings.
 

OVERKILL

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Just don't build them on a fault line like they did in California.
If we are talking about Diablo Canyon, it's seismically qualified for the location. The current shutdown plan for it hinges not in anything pertaining to seismology, but rather that its once-through cooling supposedly could impact marine life, which the gas plants using the same cooling, are exempt from that regulation.
 
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So why is it being decommisioned again? All power plants impact marine life. If only by the heat of the discharge water.
In fact, most marine life LOVES it.

I suppose it's not like California needs the power or anything. It only produces 9% of the states needs.
 

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So why is it being decommisioned again? All power plants impact marine life. If only by the heat of the discharge water.
In fact, most marine life LOVES it.

I suppose it's not like California needs the power or anything. It only produces 9% of the states needs.

They imposed some new regulation that bans the use of once-through cooling, which is the reason given to kill the plant. This is betrayed by the fact that they've given exemptions to gas plants that are doing the same thing.

Mark Nelson has a piece on this. If you are interested, I'll dig it up for you.
 
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If we are talking about Diablo Canyon, it's seismically qualified for the location. The current shutdown plan for it hinges not in anything pertaining to seismology, but rather that its once-through cooling supposedly could impact marine life, which the gas plants using the same cooling, are exempt from that regulation.
California (wrongfully) classifies natural gas as a "dirty" fuel, while it (wrongly) classifies diesel as "clean." Politics and ignorance go hand in hand. If a utility wanted use the Pacific Ocean as cooling for natural gas turbines, one would have to ask why? You are joining facts that have no relevance. IF a utility wanted to use the ocean to cool a natural gas fired powerplant, they would be prohibited in California, because the State regulating agencies classify natural gas as dirty.
 
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All the cycles except the once-through natural uranium one require enrichment and/or reprocessing facilities, which are costly, dirty and a weapons proliferation issue.

Those other cycles are presented as ultimately achieving a net decrease in the need for newly mined natural uranium, which just isn't an issue for Canada with their large uranium production.
 
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All the cycles except the once-through natural uranium one require enrichment and/or reprocessing facilities, which are costly, dirty and a weapons proliferation issue.

Those other cycles are presented as ultimately achieving a net decrease in the need for natural uranium, which just isn't an issue for Canada with their large uranium production.
Correct. Canadian mining companies would love everybody to start building these reactors, and buy their uranium. Plain truth is there are better options.
 

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California (wrongfully) classifies natural gas as a "dirty" fuel, while it (wrongly) classifies diesel as "clean." Politics and ignorance go hand in hand. If a utility wanted use the Pacific Ocean as cooling for natural gas turbines, one would have to ask why? You are joining facts that have no relevance. IF a utility wanted to use the ocean to cool a natural gas fired powerplant, they would be prohibited in California, because the State regulating agencies classify natural gas as dirty.

You can start with that document that addresses once through cooling currently in use in California and the phase-out. Of note:

The policy recognizes that some of these power plants are critical for system and local energy reliability. Some may also provide operational services (such as flexible capacity requirements, ramping to follow net load, and regulation) needed to integrate renewable resources. Owners that plan to repower their plants face additional regulatory challenges due to the lack of air credits required for new facilities or major changes to existing facilities in one or more of the air basins. To assure effective communication among the state’s energy and environmental agencies concerning the role of these plants in ensuring reliability, the OTC policy created a permanent advisory body – the Statewide Advisory Committee on Cooling Water Intake Structures (SACCWIS)1 – that is scheduled to report annually to the SWRCB. A principal function of SACCWIS is to provide recommendations to the SWRCB if the member agencies believe a delay in compliance is needed to assure reliability. Recognizing the unique circumstances of the two nuclear power plants in California that were using OTC technologies (now only one), the OTC policy also established a second advisory body – the Review Committee for Nuclear Fueled Power Plants (RCNFPP) – to refine the cost estimates for the nuclear power plants to satisfy the policy

*snip*
Over decades, the OTC plants have changed power production patterns from baseload units to load-following or peaking units, but the reality is more nuanced. Tables 1 and 2 provide annual capacity factors for the natural gas-fired OTC plants still in service in the California ISO and LADWP balancing authority areas, respectively, for 2014 to 2018. Unit-specific and cumulative (total amount for all units added together) capacity and capacity factors are provided.

And the tables:
Screen Shot 2021-10-02 at 5.11.18 PM.png

Screen Shot 2021-10-02 at 5.11.27 PM.png


You can see that California still has several plants that are once-through cooled still in service. These plants were provided exemptions due to backing up renewables; providing "system stability".

Diablo Canyon was not exempt and would be required to be converted, having cooling towers constructed, the cost for which was extremely high. The operator has decided to shutdown the plant instead.
 

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All the cycles except the once-through natural uranium one require enrichment and/or reprocessing facilities, which are costly, dirty and a weapons proliferation issue.

Those other cycles are presented as ultimately achieving a net decrease in the need for natural uranium, which just isn't an issue for Canada with their large uranium production.

That correct, that's why the foreign markets have been the marketing target for the AFCR, markets that don't have the uranium reserves we do. Alternative fuel cycles are a hard sell in Canada I suspect because of that, though OPG and Bruce Power are both financing SMR's that leverage them. We'll see where that leads.
 
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I see this as the reason: 1) US have a lot of money involved in the oil and gas industry, you don't want to encourage free energy when it competes with your bread and butter, which is why most oil states have problem endorsing Tesla or EV. 2) Proliferation risk is also a benefit for the nuclear based defense business. Having enrichment requirement means the civilian based enrichment facility can be dual use for military based reactor like subs and carriers. I fail to see why everyone pitch those tiny reactors replacing coal when they need to enrich to 20% or so, and how can that be cost effective compares to building a bigger nuke that only needs 5% or so with existing design.

Since India and China need those cheap electricity, are oil importers, and aren't in the defense pact with US, they would rather go alone on the newer design that suits them better, something purely civilian and better, like Thorium, breeder, fast reactors.
 

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I see this as the reason: 1) US have a lot of money involved in the oil and gas industry, you don't want to encourage free energy when it competes with your bread and butter, which is why most oil states have problem endorsing Tesla or EV. 2) Proliferation risk is also a benefit for the nuclear based defense business. Having enrichment requirement means the civilian based enrichment facility can be dual use for military based reactor like subs and carriers. I fail to see why everyone pitch those tiny reactors replacing coal when they need to enrich to 20% or so, and how can that be cost effective compares to building a bigger nuke that only needs 5% or so with existing design.

Since India and China need those cheap electricity, are oil importers, and aren't in the defense pact with US, they would rather go alone on the newer design that suits them better, something purely civilian and better, like Thorium, breeder, fast reactors.

What are you calling “free energy“ ?
 
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The perception that fusion is pollution free, sorry I forgot the word pollution in there.
Isn't it? I was under the impression that it is. I suppose the polluting part is the making of the fuel. Right?
 

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Isn't it? I was under the impression that it is. I suppose the polluting part is the making of the fuel. Right?
If we are talking about lifecycle emissions (which is the global standard) you have to look at the inputs used to construct the facility as well, fab the fuel...etc. Solar has no direct emissions for example, but its lifecycle emissions are 45gCO2/kWh. Wind turbines (onshore) are 11 or 12 (offshore) while hydro is pegged at 24, but that will of course vary depending on the type of hydro (that's the IPCC average). Traditional nuclear is listed as 12, but depending on the fuel cycle and source of uranium can be as low as 3.8 (CANDU).
 
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If we are talking about lifecycle emissions (which is the global standard) you have to look at the inputs used to construct the facility as well, fab the fuel...etc. Solar has no direct emissions for example, but its lifecycle emissions are 45gCO2/kWh. Wind turbines (onshore) are 11 or 12 (offshore) while hydro is pegged at 24, but that will of course vary depending on the type of hydro (that's the IPCC average). Traditional nuclear is listed as 12, but depending on the fuel cycle and source of uranium can be as low as 3.8 (CANDU).
Fun fact: not all pollution are CO2 based, and I am not sure if we have a way to quantify NIMBY pollution like turbine or nuke plants killing local real estate value, or hydro get their local population evicted etc.
 

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Fun fact: not all pollution are CO2 based, and I am not sure if we have a way to quantify NIMBY pollution like turbine or nuke plants killing local real estate value, or hydro get their local population evicted etc.
Yes, absolutely, there are other emissions, some of which are really serious pollutants (which CO2 isn't). The international community has of course latched on to CO2 as "it" in terms of what needs to be tracked, so as far as standards go, that's why I cited that figure.
 
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Nuclear power is potentially the only power source that can, if desired, be carbon negative. It would take using some of the energy produced to pull CO2 from the atmosphere (remember Carl Linde "pronounced lin-deh" figured out how to do this in the late 1800's, yes Linde gasses company) and then separate the carbon from the oxygen. While energy intensive, it is possible, even feasible, and could possibly use the waste heat from certain power plants.
 
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Nuclear power is potentially the only power source that can, if desired, be carbon negative. It would take using some of the energy produced to pull CO2 from the atmosphere (remember Carl Linde "pronounced lin-deh" figured out how to do this in the late 1800's, yes Linde gasses company) and then separate the carbon from the oxygen. While energy intensive, it is possible, even feasible, and could possibly use the waste heat from certain power plants.
Instead of using energy to pull CO2 from atmosphere and then break it down I think it is better to move energy intensive stuff (or population) there and use it directly instead of burning oil or coal to produce energy. Of course politics would prevent that from happening.
 
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