What's the pattern of I-135 and xe-135 removel in MSRE?

[Lars]

Wikipedia, Webelements, and Google all agree that that AgI has a melting point of 558 degrees Celsius. (perhaps your source said 1036 F). It will melt off before silver will melt.

You guessed my error exactly.

But is it bad if the AgI melts before Ag? Seems like that is a good thing. It flows to the fission product liquid pool and is chemically bound so it isn't a significant risk for widespread environmental radioactive release.

Also, if it drips off the silver donor then seems like we get fresh silver surface to collect more iodine.

I'm thinking of a filter (kinda like the home furnace filters) with the gas flow pushing down to encourage the AgI to drip down the a liquid collection pool at the bottom (along with the Cs).

[Cyril R]

But is it bad if the AgI melts before Ag? Seems like that is a good thing. It flows to the fission product liquid pool and is chemically bound so it isn't a significant risk for widespread environmental radioactive release.

Also, if it drips off the silver donor then seems like we get fresh silver surface to collect more iodine.

I'm thinking of a filter (kinda like the home furnace filters) with the gas flow pushing down to encourage the AgI to drip down the a liquid collection pool at the bottom (along with the Cs).

This might work. What we get is liquid Cs and AgI, in a bed that has NiF2 pellets, that get reduced by the Cs -> NiF2 + 2Cs = 2CsF + Ni. We have to make sure the AgI doesn't clog up this bed (by keeping it as hot as the Ag trap). There may be a useful AgI-CsF eutectic that allows all the reaction products to be in a drainable liquid form.

Molten AgI may be corrosive, something to check.

[Cyril R]

Does iodine dissolved in a fluoride melt react with silver? If so, this may be a way to trap it. One might consider a silver noble metal filter, where the iodine reacts to silver iodide, and is then stuck in that filter. Mp. of 558C is just enough if the cold salt is operated slightly below this (say 550C). Pass some of the cold salt through the silver filter. Perhaps we may even trap some of the precursor Te-135 (half life 0.5 minute) before it turns to I-135, in this filter. If the iodine trap is good enough, active helium sparging could be eliminated.

Will AgI dissolve or dissociate in a redox controlled fluoride melt environment?

[Lars]

Yield is around 6% IIRC so we want to pull out around 35 kg worth of iodine per GWe-year.

Half-life of 135I is 6.57 hours so we would want to process the whole fuel salt every 3 hours or so to get 75% of the iodine.

I suppose when the 135I decays to 135Xe we will lose our AgI so there will be an offgas and a return to silver. Perhaps we collect offgas from the outflow of such a cold iodine filter and thus we get automatic cleaning of the silver and collection of the Xe without pushing lots of He bubbles through the core. This would require sufficient silver surface area to collect 6.57 hours worth of iodine or around 30 grams. It would also require a way to collect the offgas. The flow would be very much lower (~200x) so the intense heat is proportionately reduced.

[Cyril R]

If the process is simple bypass flow through a filter, then 3 hours is no problem at all. You'd need less than 1% bypass flow of cold salt, that's childsplay.

The bigger question is will it work submerged under salt. Will AgI form in a submerged filter and will it stay there if salt contacts the filter? It might form as fluorine seems to have no affinity for silver, but AgI is a halide salt that may be soluble. Anyone have solubility data for AgI in fluoride melts?