Smelting Associated with the Advanced Spent Fuel Conditioning Process Page: 4 of 7
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The vapor pressure variation of chloride compounds with temperature is shown in Fig. 3. The
significant increase of vapor pressure is found above 900 C. Considering the vaporization behaviors
of chloride compounds, the removal of residual salts at 950 C was set up for the 1st step of smelting.
The metal elements in the targets of smelting have relatively low vapor pressure compared to chloride
compounds. Actually, the vaporization of U and Pu is negligible during the smelting process. However,
Am is a very peculiar element which has a very stable gas phase ground state and accordingly shows
high vapor pressure. To prevent the vaporization of Am, the heating condition should be carefully
controlled. Mn shows similar vaporization behavior of Am. Therefore, Mn was used as a surrogate
material for Am in this study.
2400 - 0.6 -
2100 CSC - Am
-U- LCI 9 0.5 - Pu
c 900 0.2
' 600 -
0 300 600 900 1200 1500 0 300 600 900 1200 1500
Temp. (C) Temp. (C)
Fig. 3. Vapor pressure changes of the target materials of the smelting with temperature.
The surface of metal powder can easily be attacked by oxygen in the oxidative condition and the
resultant oxide layer will inhibit the melting of metal powder. Therefore, the smelting should be
carried out at much higher temperature than the melting point of U. Removal of volatile materials will
be facilitated in vacuum condition by enhanced diffusion rate. Fig. 4 shows the vaporization behaviors
of some characteristic materials during inactive experiments conducted by using induction furnace.
The final temperature was kept for 5 hours in the vacuum condition of ~10-2 torr. Chloride compounds
except SrCl2 were completely removed from metal product during the 1st step of smelting at 950 C.
The vaporized chlorides will be transferred to the salt waste treatment process. Mn, the surrogate of
Am, and SrCl2 were partially vaporized at 1,500 C. The separation of Am from the metal ingot is not
desirable. The lowering of the smelting temperature or decrease of the vaporization rate by increasing
the pressure inside the smelter can be an effective method for the prevention of Am vaporization. The
further study to get quantitative data on the vaporization behaviors of Am and SrCl2 will be carried out
to optimize the operation of the smelter.
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Hur, J-M.; Jeong, M-S.; Lee, W-K.; Cho, S-H.; Seo, C-S. & Park, S-W. Smelting Associated with the Advanced Spent Fuel Conditioning Process, article, October 3, 2004; United States. (digital.library.unt.edu/ark:/67531/metadc785482/m1/4/: accessed October 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.