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3 Fluoride Salt Chemistry, Partitioning, and System Corrosion
Pages 37-44

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From page 37...
... The LiF and BeF2 components were chosen to be thermodynamically more stable than UF4, with a liquidus temperature for the flush salt of about 460C. The 4.9 mole percent ZrF4 in the fuel salt reduces the liquidus temperature slightly but otherwise serves two functions: 1.
From page 38...
... . The fuel salt solids can be viewed as a matrix of closely packed fluoride ions with the much smaller Be2+ and Li+ ions occupying interstices.
From page 39...
... . This gaseous product results from radiolysis reactions in the solidified salt phase, and it would be prudent to assume that UFO has been distributed to, and condensed in, all regions of the system, including the freeboard volume in the upper regions of the drain tanks as well as areas of restricted flow in the off-gas vent system preceding the auxiliary charcoal bed (ACB)
From page 40...
... Several chemical options can be considered for the removal of nonvolatile uranium residues remaining after the initial pumping. Considerable fluorination technology that has been developed over the last 20 years at other Department of Energy (DOE)
From page 41...
... The results showed that very little plutonium was removed, even after most of the uranium was volatilized as UF6.3 Furthermore, the high-temperature fluorination yield of PuF6 was low, and long fluorination times caused increased corrosion. These results are consistent with the understanding that, because PuF6 is a powerful fluoridating agent, little PuF6 would be expected to be volatilized from the molten salt phase until all other volatile fluoride gases (including all the UFO)
From page 42...
... Since oxygen gas has a low solubility in the molten salt, addition of sodium carbonate to the molten salt has been found at Los Alamos to be a suitable way to precipitate the plutonium-americium oxides. If the MSRE molten salt is sufficiently fluid to be either filtered or centrifuged to separate a precipitate of zirconium-plutonium oxide, the method utilized at Los Alamos may be an applicable technique for isolation of the small amount of plutonium present in the MSRE drain salt.
From page 43...
... ORNI, corrosion researcher James Keiser inspected one valve that had been plugged and cut out of the system and found no evidence of observable corrosion attack. As one possible means of observing on a gross scale the condition of the Hastelloy and the salt inside the storage tanks, an optical fiber inspection system could be considered.
From page 44...
... The ideas4 presented below are offered for consideration by ORAL staff to weigh the merits of obtaining this information against the time and efforts required for meaningful results. Corrosion tests would be conducted over irradiation times short compared with the 27year radiation exposure of the fuel tank walls, even though the integrated dose could be similar.


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