In Nuclear Power, Size Matters

PerlJedi writes "Most nations with nuclear power capabilities have been re-assessing the risk/benefit of nuclear power reactors following the Fukushima plant melt down, a newly released study suggests the U.S. should expand its nuclear power production using 'Small Modular Reactors'. 'The reports assessed the economic feasibility [PDF] of classical, gigawatt-scale reactors and the possible new generation of modular reactors. The latter would have a generating capacity of 600 megawatts or less, would be factory-built as modular components, and then shipped to their desired location for assembly.'"

Comments

Re:right idea - Wrong fuel

[denis-The-menace]

/. ate my link
http://thoriumremix.com/2011/

Citation?

[Anonymous Coward]

I work as a consultant for electricity planning, and I have *never* seen a single survey which shows that folks who live near a nuclear plant are in favor of new units being built at the site. Not a single survey. Not even for Vogtle units 3 and 4, being built right now next to units 1 and 2, located on the Georgia-South Carolina line... a place where I'd expect a more favorable response than most.

If you've got one, I'd love to see it.

Re:right idea - Wrong fuel

[vlm]

Theres a whopping big wiki article that tries a little too hard to be "balanced" when in all fairness Th is a PITA fuel, that kinda sucks.

Its only good for non-proliferation from a distance. Up close its worse. You need to boot up with a slug of Pu because there are no fissile Th isotopes. So no one ever builds "a Th reactor" they build a "bomb grade Pu reactor" surrounded with a Th shell that eventually can breed itself into reacting, hopefully your breeding plan curve matches your electrical demand curve.

Its only good for non-proliferation if you define proliferation as current designs. Historically plenty of U233 bombs were blown and research done. No you cannot make a current model US B61 out of stuff from a Th reactor. Yes, you can make something almost as good as a B61 that is U233 based using what comes out of a Th reactor. It in no way prevents proliferation merely makes it a slightly more involved research project (slightly!)

In a way, not being useful for proliferation dooms Th. The US and Russia and China and god only knows who else (Iran?) are still going to need U based reactors so now you've gotta run both technologies... Why not just run one? And that one's gotta be U, at this time. So trying to push Th means your sales will be pitiful because you can only sell to 3rd world and not much else.

Plus it gives the non-proliferating Th owners experience in plant operation which they can transition to new/secret U plants of their own anyway, its like bootstrapping proliferation not preventing it.

Anyone who says Th = nonproliferation is either misinformed or being paid or trolling.

Its an unholy PITA to recycle due to hard gammas, or you can have agony when disposing. Its waste stream is just "worse" than a traditional reactor.

Its harder to run, more neutron poisons like Pa build up.

To be economical, you just have to burnup into the ground, which is kind of like saying a F-350 has a lower lifetime environmental cost IF you can get it to survive 600K miles. Its... ambitious. You don't achieve high burnup by just wishing, its difficult, dangerous if you have cladding failures, and expensive. Otherwise the prius wins again for overall lifetime costs.

Its interesting to learn about, good to learn about, but it shows good engineering judgment to avoid a Th design.

Re:Toshiba 4S

[DerekLyons]

You forgot "and it's pretty much vaporware", never having been tested or proven in hardware.

You obviously didn't watch the video...

[andersen]

They are NOT at suggesting using solid thorium and making fuel rods. That would indeed be truly stupid.

The LFTR uses thorium dissolved in molten floride salt. It is proven tech, since the US government
built one back in the late 60s and ran it for 5 years -- with 1.5 years at full power...

Watch the video http://thoriumremix.com/2011/
then and only then can you properly comment on thorium....

Re:You obviously didn't watch the video...

[BlueParrot]

The LFTR uses thorium dissolved in molten floride salt. It is proven tech, since the US government
built one back in the late 60s and ran it for 5 years -- with 1.5 years at full power...

The devil is in the details.

While it is indeed possible to build an LFTR, that old bugger called economics tends to come and mess things up.

First of all you need a larger amount of fissile materials since the molten salt transports it out of the core. and around the entire primary loop. Secondly, as with sodium, you need to have a secondary loop to make things safe. Then there's the hydrolysis that can occur at low temperatures, which means you have to keep the salt molten. If the reactor has problems, that may involve drawing power from the grid. The reprocessing technologies kinda work, but are unproven at large scale, and nobody has an idea what the cost will be for a large reactor. They also imply building reprocessing tech for every single plant, which increases capital costs.

Then there is the startup material. Natural uranium is not good enough, so you either need to breed U-233 in a different reactor ( proliferation concern ) , use highly enriched U-235 ( proliferation concern, expensive ) , or startup on plutonium. Now plutonium in a thermal spectrum leads to accumulation of Curium, which is a troublesome waste product that cannot be efficiently destroyed in a thermal reactor.

Add in that while Thorium and Uranium dissolves easily in fluoride salts, plutonium and the other actinides do not. In fact, even at high temperatures with a completely pure salt, the solubility of Pu fluorides is just a few percent. The molten salt reactor experiments got around these issues by using a very exotic salt. Beryllium and Lithium fluorides, with the lithium enriched in Li-7. Now, beryllium is highly toxic, expensive and difficult to work with. It's such a pain that the US and UK considered developing new nuclear warheads that did not use it, even though it is the best lightweight neutron reflector there is. Enriched lithium-7 is a different problem in itself, and even if 99% pure, you will get quite a bit of tritium when it is exposed to neutrons. Perhaps not more than in a CANDU reactor, but all tritium control systems ever designed are made for water coolant.

Then is the issue of in-core materials. The molten salt reactor developed by the US dealt with damage to in-core materials by replacing the graphite core materials frequently. Not only is this expensive, but it's not very fun to handle radioactively contaminated graphite. It is hard to reprocess since it forms organic compounds and is difficult to dissolve in nitric acid. Pyro-processing by electro-refining and similar is also poorly suited for graphite. This is one of the reasons why the pebble bed reactors are usually seen as "once through". Nobody has come up with a practical way to deal with the graphite. Since the material will be in direct contact with the fuel salt, it will likely adsorb quite a bit of contaminants.

Plateout on heat exchangers is another issue. The noble metals have poor solubility in fluoride salts, so unless a very potent ( i.e expensive ) reprocessing system is able to get rid of them quickly, they will plate out on the cold parts of the reactor, which is usually the heat exchangers. A suggested solution is to use graphite-based heat exchangers, which has its own spectrum of development issues and research needs.

I'm not saying molten salt reactors can never become a good idea. I'm just saying that in comparison to the number of issues that need to be resolved to make them practical for a power plant, they are extremely hyped.

Re:Cheap energy saves lives.

[Solandri]

The problem is rather: Where do you put all that irradiated waste, ranging from water over metals, concrete, oils, various sealants and so on? After all, most of this stuff happily glows for a few decades at minimum and hundreds of thousands of years at the upper echelon.

The problem is, we ask these questions only of nuclear.

Of course things like coal, gas, etc. are not better -- especially regarding the climate. But at least they don't cause such extremely permanent issues that we can't even imagine a kind of physical or chemical process to get rid of it.

The elemental mercury released by burning coal sticks around not for years, or decades, or hundreds of thousands of years. It sticks around practically forever. At least as long as it'll take for current organisms to absorb it, die, and turn into coal themselves. Yet we're happily pumping it into the atmosphere because we're too afraid of nuclear.

Each year, the U.S. generates about 2000 tons of spent nuclear fuel (high level radioactive waste) in exchange for ~20% of its electricity. By volume that's about two tractor trailers. This is the stuff which can potentially be dangerous for thousands of years. (The 10,000 to 100,000 year stuff lasts so long precisely because it has low radioactivity. By the time it got that old, it would no longer be high-level waste, contrary to what anti-nuclear activists like to imagine.) This "waste" could actually be used as fuel in breeder reactors, reducing the total amount of "high level radioactive waste" to just 1/10th or 1/20th what we currently generate.

But because we're scared to death of what to do with such a small quantity of nuclear waste, we continue to pump into the environment billions of tons of coal ash, including mercury, CO2, radioactive uranium and thorium, and a host of other nasty materials which together kill an estimated 250x as many people as Chernobyl every year. That is what saddens me so much about the energy situation. Yes long-term we should be working towards renewables like wind, geothermal, solar. But while we are working towards scaling those up and making them cost effective, it is absolutely criminal not to be switching out our fossil fuel plants for nuclear. Environmentalists have fabricated a false dichotomy between nuclear and renewables, where we must choose either nuclear or rewnewables. There is no such choice. We can switch to nuclear while we continue to work on renewables.

And if you finally arrive at hydroelectric, geothermal, solar and wind generation, the scope of the problems you cause by running them can be measured in "less than a decade" for cleaning up a broken dam and "what problems?" for solar and wind

Just how do you define "problem"? People see the evacuation zone around Fukushima as a problem. A hydroelectric dam creates a permanent evacuation zone behind it larger than Fukushima's. It's called a reservoir. Why is vacating people for one bad, while the other acceptable? Because one has the N word and the other is just water? Water kills nearly 100x more people each year than nuclear power has in its entire history. So which is truly more dangerous?

Measured in lives lost per unit of energy generated, nuclear is by far the safest power source. So your "less than a decade" and "what problem" assessments are only accurate if you assign zero value to people's lives.

Re:right idea - Wrong fuel

[BlueParrot]

1. With LFTR you have next to no waste.

Other than all the fission products, including radioactive iodine, strontium and caesium (and others). Heck, just avoiding excessive tritium production involves isotope separation of lithium to enrich it in Li-7.

Essentially somebody has not told you teh full truth, or outright lied.

2. Uranium has an [Expensive] established fuel chain. You can only get fuel pellets from ONE supplier: the one who built the reactor. And no, they don't have sales.

Fuel costs are less than 10% of the cost of nuclear power. Construction and operation is the majority of it. Most estimates conclude that reprocessing ( even in the LFTR ) would be more expensive than uranium enrichment. You may save some money by not needing fuel manufacture , but in return you have a larger inventory of fissile material since it is not all in the core.

3. Advantage of thorium vs uranium:
-No enrichment
-No 10000 year radio-active waste

Nonsense. Thorium is not fissile, so it needs to be started on a large seed of fissile material. This could be either reprocessed plutonium or enriched uranium, just as with other reactors. Also, since plutonium cannot be effectively destroyed in a thermal spectrum, there will be a buildup of plutonium and curium, both of which have half-lives in the range of thousands of years, while still be very toxic.

-No high-pressure water cooling schemes that need power to work and backups up the wazoo.

Most modern designs, whether they use water or some other coolant, are built to not need power for emergency cooling.
The ESBWR doesn't even use pumps during normal operation. This is not a feature of thorium, but a general property of
decent engineering. Hot liquid flows up, cold comes down. This has been demonstrated successfully in virtually all types
of coolant, including water, lead, sodium, salt and carbon dioxide and even nitrogen.

You may have a point about pressure, but there are other issues with salt systems. The need to keep the salt above it's several
hundred centigrade melting point is one of them.

-Others mentioned in the video

There's loads of videos. Most of them are half-truths at best, and I'm not just talking about reactors. Seriously, you seem to never have come across a marketing campaign before.