ThorCon Power
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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.
" 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 :)
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.
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...
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.
What they have done, though, which is still very cool, is use thorium instead of uranium in a conventional nuclear reactor.
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.
At that point you can just let it sit there "forever" if you want. Not that you would of course, you'd want to clean it up.
If the drain between the core and the drain tank fails AND the both other passive cooling methods fail to keep the core cool enough then yes eventually the core vessel will fail. In that case, the fuel escapes the first containment (the primary loop) into the can. The can drains to the fuel drain tank so we still provide cooling.
The alternative is a Fukushima-style transition from "working reactor" to "unapproachable death trap generating clouds of hydrogen gas which can explode the containment dome, sending toxic radioactive smoke from uranium fires into the atmosphere (while other material leaches into the ocean via the water table)". Even Fukishima's spent-fuel cooling ponds required water be added for for weeks and weeks on end.
If you'd like it to keep the reactor working while walking away from it, that's another matter which is keyworded something like "unattended operation" not "walk-away safe".
Also, what happened to that experimental reactor? Didn't Obama send it to Norway or something?
The second problem was with tellerium penetrating the Hastalloy and weakening it at the grain boundaries. This isn't a problem with stainless steel.
The stainless steel planned is SS316 which is available from multiple sources.
The primary loop does not have insulation surrounding it but it does have a 1m thick graphite reflector to bounce most of the neutrons back to the core then a layer of B4C to absorb the rest before they get to the vessel.
The MSRE was shutdown decades ago and recently had its fuel salt removed. The vessel and piping are still in Oak Ridge inside its concrete silo.
I only have two things to say: 1.) Good luck testing and gathering data on these ideas. You'll need it. 2.) Are you hiring mechanical engineers?
These in turn are inside a silo, which is inside the silo hall. All total there are four barriers to break through before we get radioactive release.
Further, the fission products are combined with fluoride upon forming (when you fission UF4 the uranium is split into two fission products and the F4 is available for recombining with the fission products). Most of the fission products like to stay in the salt so even if the salt gets spilled the fission products won't wander farther than the salt spill.
Molten salt corrodes stainless at a rate of 0.025 mm / year. The solution: make the walls thicker, change out and inspect the primary vessel and plumbing every 4 years; you get 40 years per millimeter.
This has a pretty good overview: https://www.youtube.com/watch?v=P9M__yYbsZ4
We should start with an understanding of how much waste is there currently from today's reactors. Roughly one coke can would hold all the waste generated from one person's electricity (European standards roughly 1kW) for a lifetime. We can reduce the volume of waste readily by removing the uranium and re-enriching it. This can be done with virtually all reactors including todays reactors. This will remove 90% of the waste volume but does nothing to reduce the hazards of the waste.
We can remove the elements that are heavier than uranium (transuranics or TRUs). This is the long term hazard. This material can be recycled into a reactor to be fissioned (destroyed forever not simply buried). This can be done to a very limited extent in some of today's reactors. But either IFR or molten salt reactors would really be the appropriate way to eliminate the long term hazards of nuclear waste. Such a process will be limited by our ability to separate the TRUs from the fission products. We expect to achieve around 99% separation so to reduce the long term hazard 100 fold.
The near term hazard comes from the fission products. These will decay in a reasonable time. Every 30 years the radioactivity will decay by half. So by 300 years you are back to roughly background radiation. 300 years is short enough we know how to build containers to last that long.
How does this compare to traditional nuclear power and other forms of power generation?
You have to put up quite a few windmills and solar panels to get to such numbers.
On the other hand, the Olkiluoto three 1,6 GW nuclear plant has taken more than a decade and countless billions and still isn't ready.
Instead of shipping containers, my thought was on using the existing rail systems, although that's very US centric.
What's the next step? What can the HN community do for you?
edit: more specifically, it's not about making it look more expensive/complex/modern but moving away from the specific aesthetic it has right now
Also, anything that could deliver radioactive waste to the sun could deliver it to a major city just as easily.
http://www.reddit.com/r/askscience/comments/2r43nl/why_dont_...
It uses molten salt as the catalyst for nuclear reaction, using thorium as the fuel.
The molten salt allows passive safety measures, significantly reducing the negative effects of a meltdown. It also significantly reduces the size of the reactors housing.
The use of thorium allows for significantly cheaper nuclear fuel, which happens to be very difficult to convert to weapon-grade nuclear fuel. By very difficult, I mean very difficult for a nation state, let alone a small group of bad actors.
Yet, LWR is still the dominant design. So, what's the catch? There's clearly something preferable about Uranium LWR that causes their dominance, no?
After Fukushima, I don't think most people would agree the risks are well understood, at least as reflected in the actions of the nuclear industry and its regulators.
The NRC (and hence most of the world's regulators) uses a "design basis" approach to establish what emergencies reactors should be able to respond to safely without the release of radioactive materials. The design basis is supposed to quantify the known risks.
In 2011 we saw just how inadequate the design basis framework was. It failed to predict risks such as multiple systems failing simultaneously, emergency generators being flooded, the plant being cut off from external help, multiple meltdowns happening simultaneously, valves getting stuck open, and a litany of other things that actually happened, resulting in the level 7 accident we saw.
While the exact set of events that happened at Fukushima Daiichi is unique, similar accidents could happen in the US, or indeed anywhere (e.g. many reactors are downstream from major dams and could theoretically experience catastrophic flooding).
And just as the NRC's computer models deemed Fukushima impossible before the accident, the NRC has largely ignored the recommendations of its own near-term task force in how to improve the regulatory situation in the US after the accident.
It is up to us to demand that the nuclear power industry, which is wielding technology of massive destructive power at the behest of its shareholders, transform itself into the transparent, accountable industry we deserve.
Still, the US Airforce wanted a nuclear-powered bomber shortly after the Navy showed their nuclear sub and before ICBM's deprecated "end-of-days" long-range bombers. A water-contained reactor wouldn't work in an airplane, so they funded the development of the MSR (molten-salt-reactor).
Unfortunately, when they shuddered the project after the implementation of practical ICBMs, industry politics discredited MSR's in favour of the reactor-types we have now.
After fukushima, a grassroots campaign has been undertaken to resume research of MSR's as a replacement of fossil fuels for scalable carbon-free energy creation. If you are interested, you can get a great overview here: https://www.youtube.com/watch?v=P9M__yYbsZ4
So essentially what you're seeing is the result of decades of regulatory capture of the NRC by the nuclear industry.
Most of the alternative reactor designs have more going on in the radioactive part of the system, or more difficult working fluids. This usually leads to trouble. Sodium-cooled reactors have sodium fires. Helium-cooled reactors have helium leaks. Pebble bed reactors have pebble jams. (The one in Germany is so jammed it can't be decommissioned.) Molten salt reactors have to pump radioactive molten salt around and run it through a chemical processing plant. In some designs that salt is a fluorine compound. Now you have all the headaches of operating a radioactive chemical plant.
Most power utilities don't want to operate a radioactive chemical plant.
Most power utilities don't want to operate a radioactive chemical plant
This is a brilliant phrase, thankyou.
http://thorconpower.com/features/clean says:
> And ThorCon obtains about 25% of its power from easily mined thorium which requires no enrichment.
http://thorconpower.com/design/thorcon-can says the "fuelsalt" is "a mixture of sodium, beryllium, uranium and thorium fluorides called nabe".
In such an event, an MSR has a "drain tank" that sits below the reactor. In an emergency, gravity drops the salt into the drain tank, and the nuclear reaction safely comes to a halt- all with zero human intervention.
I'm surrounded by vehement anti-nuclear types, you know the ones who get arrested for their environmental activism antics. When talking about nuclear technology with them I find it helpful not to utter certain words like 'meltdown', 'weapons', etc etc.