Magis wrote:The low-pressure, low(ish)-temperature state of the liquid fuel during normal operation will not necessarily be maintained during any kind of accident. Sustaining its operating temperature requires control over both the fission reaction rate and cooling system. If the cooling system fails (hmm... where has that happened recently?), then the temperature of the liquid fuel will increase, and may increase catastrophically. Even when the cooling systems are working just fine, a power excursion could bring the fuel to thousands of degrees in an instant. Flash-boiling however many tons of fuel is going to breach the piping system - period. Not that boiling is even strictly necessary. Even in a liquid state, increased temperature will lead to a density (and thus pressure) change.
heh, I was asking about the properties of the salts used for a reason.
The interesting thing about a liquid reactor is that you can spread the core on a much larger surface area (either around the broken core or by dumping it in a specifically-built container), thus allowing it to cool itself passively-ish. In case of total cooling failure a normal reactor will melt through anything.
someone_else wrote:Once this gas escapes the reactor somehow, is cooled by contact with the fucking surrounding air (not anywhere close 100 degrees, go figure 1000+ degrees like required by the salt gas to fucking stay gaseous) to well below its liquid state temperature, then you have to deal with very stable salts that won't dissolve in water. And this well before it could manage to get close to a wall.
You have no grasp of how much cooling is necessary for nuclear fuel if you think that
natural convection to air is going to get the job done.
Nonono, stop. the above was an answer to your "
Oh, except with this thorium reactor, instead of just mildly radioactive coolant vapor bursting out, it's an incredibly lethal fume of nuclear fuel and tons of fission and activation products." You were talking about superheated gaseous salt escaping the core and talking about how dangerous would that be. Which is kinda bullshit since that gaseous salt is going to be so hot that contact with anything (like air) would cool it down to (still impressive) temperatures, but at those temps the salt is liquid at most, so it will fall down.
Assuming the liquid fuel that escapes into the building is in a non-critical formation, it will still be generating heat at a rate equivalent to 7% of full-power. So, assuming a 3000 MW-th core, you'd be looking at 210 MW of heat generated in the fuel. Good luck trying to keep that temperature down just through contact with air or other building materials.
I frankly don't know enough, but the designs of Flibe energy have a pan where they can drain the entire reactor onto and they say the pan is designed to cool the fluid passively. Making one under the reactor in case of issues doesn't sound so strange. Is that made of handwavium?
I think the outrage from nuclear experts would have reached obvious levels if it was blatant handwavium.
there are kinds of concrete or materials that can dissipate thermal energy faster.
Not to mention that in the meanwhile, fission product gasses will be flooding the entire facility killing every operator/electrician/janitor in its path.
Why should this happen? Isn't the manned area relatively far from the reactor contaiment buildings?
Besides, thorium fuel cycle generates only 1/6th of the transuranics of uranium fuel cycle. So you are looking at much less stuff.
Given that heat after the reactor stops being critical is generated by decaying stuff, should that mean that decay heat is only 1/6 of a uranium reactor? Because that would bring down your 210 MWt to 35 MWt. Big difference.
But you are the expert here. So feel free to say I'm wrong.
Here's an idea: instead of this batshit crazy liquid fuel design that has substantial safety issues and no immediately obvious benefits, how about the world continue to build solid-fuel reactors that, you know, work.
The benefits are massively cheaper construction, massively cheaper fuel (no enrichment needed), easy reprocessing that can be done with a small chemical plant at the facility, much more limited amount of nuclear waste to be handed to italian organized crime that sinks it with old ships in the mediterranean, proliferation resistence. It does have some safety issues but it avoids others.
I thought I read that a modern solid-fuel reactor will repay the investment in 30-40 years, an investment of double-digit billions and building times measured in decades, assuming no cost overrun and no fuckup (and also assuming no semi-slave-labor like china). But no, we don't need something cheaper and simpler.
Besides, there is another design you may find more close to your tastes, the (warning, pdf)
ADTR offers the same benefits of LFTR without the molten salt part, and avoid the issue of finding highly enriched stuff to kick off the reaction by using an accelerator to bombard the reactor core with neutrons (and can also dial its power production by varying the accelerator output).
