Chelant screening and refinement tests - Phase I, Task 2. Topical progress report, December 1993--June 1994 Page: 54 of 236
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In test 68, Solvent B (EDTA-carbonate-peroxide) was applied in the same manner as that
in Test 67 (high temperature application at 66*C). At the conclusion of the two-hour room
temperature exposure, the uranium concentration of the solvent was 3.50 grams per liter.
During the four-hour exposure at 66*C, the uranium concentration of the solvent increased
slightly to 3.82 grams per liter. The solvent was then cooled to room temperature and spiked
with hydrogen peroxide. The test flask was held at room temperature for two hours, during
which time the uranium concentration decreased slightly, to 3.72 grams/liter. This apparent
decrease is due in part to the dilution of solvent through addition of peroxide, as well as normal
analytical variance. This application sequence resulted in essentially 100% dissolution of the
added uranium dioxide. As expected, the coupons experienced considerable general corrosion,
as determined by weight loss (carbon steel 0.918 mils, nickel 0.069 mils, Monel 0.122 mils).
Test 70 was a repeat of Test 68, except the high temperature application was performed
at 93*C. Results for this test were very similar to those for Test 68; again, that the uranium
appeared to go into solution slightly more slowly than in the first test of the EDTA solvent.
After two hours at room temperature, the solvent contained 2.31 grams dissolved uranium per
liter. The concentration increased to 3.36 grams U per liter after one-half hour of the high
temperature exposure. Again, as in Test 69, the temperature increase during heatup appeared
to catalyze the uranium dissolution reaction. The uranium concentration of the solvent increased
slightly throughout the remainder of the test. A graphical representation of test results appears
at Figure 10. Note that the dissolved uranium concentration increased slightly after the peroxide
spike after cooling to room temperature. At the conclusion of the test, 100% of the added
uranium dioxide had been dissolved; the coupons experienced considerable general corrosion,
as determined by weight loss (carbon steel 1.405 mils, nickel 0.196 mils, Monel 0.124 mils).
The results of testing on Scenario #1 indicated that requirements for uranium dissolution
efficiency could be met by either solvent using this application sequence. The carbonate-
peroxide solvent exhibited negligible corrosion rates as applied; the EDTA solvent showed
general corrosion rates sufficient to remove 1.5 mils of carbon steel during a four hour exposure
8.3 Testing of Application Scenario #2
The rationale for the second application sequence was that solvent would first be applied
at elevated temperature, to allow for corrosion of base metal with subsequent release of uranium
having penetrated the grain boundaries of the metal. After the high-temperature exposure, the
solvent was to be cooled to room temperature, spiked with hydrogen peroxide (which would
have decomposed at elevated temperature), and held for four hours to allow for dissolution of
Four tests (71-74) of Scenario #2 were run to evaluate each of the two selected solvents
at two temperatures of application (66*C and 93*C). An identification of the four tests follows:
Test 71: Carbonate-peroxide solvent @ 66*C
Test 72: EDTA-carbonate-peroxide solvent @66*C
Test 73: Carbonate-peroxide solvent @ 93*C
Test 74: EDTA-carbonate-peroxide solvent @93*C
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Chelant screening and refinement tests - Phase I, Task 2. Topical progress report, December 1993--June 1994, report, July 1, 1995; United States. (https://digital.library.unt.edu/ark:/67531/metadc680875/m1/54/: accessed April 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.