Sir Bobby, excellent questions to which my answers are given in detail below. Cleaning the salt: To complete the breeding cycle, there are two salts that require cleaning.  The fuel salt requires the removal of fission products that would absorb neutrons needed to maintain the chain reaction, with an excess of neutrons from each fission of U-233 that goes toward the conversion of Th-232 into Th-233.  The last species becomes U-233 after two beta-decays.   The most important  fission product to remove is Xe-135, which has a huge cross section (2 million times greater than normal) for capturing neutrons.  The isotopes of Kr are also abundantly represented in fission products and are important to remove for the same reason.  Fortunately, both are noble gases that will bubble out of the liquid salt if we sparge a carrier noble gas like helium into the pump bowl.  Next, the fissile U-233 needs to be reclaimed before further cleaning of the fuel salt.  Sparging fluorine gas, F2, into small samples of fuel salt will convert UF4 into UF6.  While UF4 is a liquid at temperatures characteristic of the fuel salt, UF6 is a gas and will, if encouraged, bubble out of the molten salt.  This step also removes compounds of volatile fission products like dangerous I-131 with an 8-hr half-life .  To separate the UF6 from the other volatile species, the vapor is passed through a powder of NaF-BeF2, which will adsorb the UF6 while letting the other gases through to be bottled and stored as radioactive nuclear waste.  By then passing hydrogen gas, H2, though the powder, the trapped UF6 is converted back to UF4 with the release of 2 molecules of HF gas for each molecule of UF4 or UF6.  The NaF-BeF2-UF4 can be put back into the reactor core as clean fuel salt, while the 2HF can be converted by electrolysis to F2 + H2.  The recycled F2 can be used to convert a new batch of UF4 to UF6 that is trapped in fresh NaF-BeF2, while the recycled H2 can be used to convert the UF6 trapped in NaF-eF2-UF6 into a new batch of cleaned fuel salt, NaF-BeF2-UF4. Where does the fresh NaF-BeF2 come from?  The small samples of fuel salt into which we sparge fluorine gas, F2, has not only NaF-BeF2, but also non-volatile fission products, some of which are extremely radioactive.  The high radioactivity will steadily try to increase the temperature of the fuel salt.  If we pump down the pressure above the contaminated fuel salt, we can vacuum-distill the fuel salt so that NaF-Be2 boils away as a gas once the temperature gets above 1000 C.  This vacuum distillation produces gaseous NaF-BeF2, which will become a liquid and then a solid as it cools down.  The pure solid NaF-BeF2 is what is made into a powder to capture the UF6 in the previous paragraph.  The non-volatile fission products left behind need to be divided into very small parcels, so that their large surface-to-volume ratios allow them to be cooled, and then converted from fluoride forms into safer oxide or silicate forms.  We put the parcels of solid oxide or silicate fission products into cold storage for up to five years, before fusing them with non-radioactive glasses to be buried for, say, three hundred years until the radioactivity decays to safe background levels. Blanket salt When we write UF4 or UF6 in the above, the U we are assuming is mostly U-233 (with a little accompanying U-232).  Natural uranium is mostly U-238 with a little U-235 mixed in.  Where do we get the U-233? The answer is from the blanket salt, which is either NaF-BeF2-ThF4 or, more simply, NaF-ThF4, with natural thorium being almost pure Th-232.  When Th-232 is irradiated by neutrons generated in the reactor core in excess of what is needed to maintain the chain reaction, the Th-232 can capture a neutron and become Th-233.  After two beta decays, the Th-233 turns into U-233.  In the blanket salt, the U-233 is in the form of UF4.  To separate the UF4 from the rest of the blanket salt, we remove a small batch of the blanket salt from the pool for off-line processing.  The processing consists of sparging F2 into the small sample, whiich converts the UF4 into UF6 that bubbles out of the blanket salt.  Unlike uranium, thorium does not have any valence state higher than +4, so the thorium stays as ThF4 and remains as a liquid in the cleaned blanket, salt which can be put back into the pool. As before, a powder of NaF-BeF2 can capture the UF6, with the combination turned into fuel salt by the methods described earlier.  Indeed, to prevent the cleaned fuel salt from dropping in U-233 concentration, we should add the UF6 extracted from the blanket salt as a supplement to the UF6 that comes from cleaning the fuel salt to make up whatever was lost by fission reactions in the core. In this way, the reactor becomes a breeder, which is self-sustaining in its fuel requirements as long as we have enough thorium in the blanket salt.

Bobby, I can understand that you find this frightening. But many things in biology and physics are frightening to amateurs (like myself.)

Are you less alarmed about nuclear weapons, now that the processes of fission and fusion are common knowledge?

If you don't trust engineers, who have a university education to even call themselves an engineer, and years of specialized work experience before they're allowed to make critical decisions,