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Comment by CurtMonash | Hacker News Reader

I took one nuclear engineering class, in 1975. It was clear then that pressurized water reactors should be replaced as the predominant design, either by gas-cooled or molten-salt. I'm sure the same is true now.

http://en.wikipedia.org/wiki/Very-high-temperature_reactor suggests that gas-cooled reactors tend to be pebble-bed, and that the story gets confused because there's a molten salt version of the pebble-bed reactor as well.

Anyhow, googling on HTGR (High Temperature Gas Reactor) will reveal more.

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They can have their own problems. The THTR-300 for instance is one of the few commercial HTGR we had. They had several operational problems like water leaking into the primary circuit (which could lead to hydrogen and oxygen buildups at that temperature). The decommissioning currently is a huge mess. Sadly the English wikipedia doesn't have as much information as the German one about it.

People have been trying for twenty years to find $300 million in government funding to create a new reference design of a modern thorium reactor. TVA's old reactor which ran until the seventies was based on forties research.

But the past three presidents have not made it a national priority. China and India have funded research and so has one private individual, Bill Gates.

It just vexes me that thorium research is not a national priority. How can a technology that, by many estimates, has at least a 50% chance of being a viable replacement of all energy needs over the next 1000 years not be worthy of the US investment? We lose hundreds of billions of dollars per year in oil imports. Why is that not worth avoiding?

It's because nuclear reactors, of any kind, are politically untenable at the moment. Especially unproven designs. Nobody's going to allow one to be built in their back yard, no matter how promising the technology.

I'm not familiar with Thorium reactors at all, so forgive me for asking: how much long-lived nuclear waste do they produce? Because we have no viable way to do with that.

They use about 1/200th amount of fuel compared to current uranium reactors, so the amount of total waste is small.

About 1 tonne thorium per one gigawatt-year.

And the wastes they produce have a far smaller portion of long lived isotopes, because the reactor controls very well what substances receive neutrons.

Here's the best image comparison I could find. http://4.bp.blogspot.com/-mAg4r-09gm0/TdZeWHzJWEI/AAAAAAAAAh... http://4.bp.blogspot.com/-mAg4r-09gm0/TdZeWHzJWEI/AAAAAAAAAh...

> I'm not familiar with Thorium reactors at all, so forgive me for asking: how much long-lived nuclear waste do they produce?

Almost none of the 250,000 year stuff. Almost entirely the 300 year stuff. Also, about 1/4 the total mass of all waste product.

Additionally, according to their documentation, the 250,000 year stuff is ultimately cycled back into the reactor to be destroyed. Most long-lived nuclear waste is fissionable, so you can just use it as more fuel, given that you can remove the fission products from the fuel easily.

The idea is that not only do they not produce long-lived waste, but some designs can even recycle the 'spent' fuel from conventional reactors.

Is this in models -- molten salt? -- where the fuel circulates in liquid form?

Norway has also put a bit of money into thorium reactor R&D, with a small modern experimental reactor currently operating on a 5-year trial: http://www.extremetech.com/extreme/160131-thorium-nuclear-re...

In fact it is an old test reactor from the 1950ies.

What they have done, though, which is still very cool, is use thorium instead of uranium in a conventional nuclear reactor.

Gates isn't working on Thorium; the TWR is a uranium / plutonium reactor.

impressive - http://en.wikipedia.org/wiki/Pebble-bed_reactor#AVR

" There exists currently no dismantling method for the AVR vessel, but it is planned to develop some procedure during the next 60 years and to start with vessel dismantling at the end of the century."

German methodical planning :)

As long as it is relatively secure, monitoring it and otherwise keeping away is probably an ok strategy. At least the half-lifes are only in the decades if I remember correctly.

That amazing piece of technology is in my birth town (or city, if you're generous).

While I never actively followed the plant's history, I do remember quite a bit of resistance, reports about potential 'leaks' and talks about it being not reliable enough.

Never been a fan of HTGRs; the problem with LWRs is pressure, and what happens if you get to much of it or have a material failure. HTGRs have the same issue (though, not the potential for thermocatalytic degredation of the fuel elements).

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