Chelant screening and refinement tests - Phase I, Task 2. Topical progress report, December 1993--June 1994 Page: 42 of 236

Corrosion coupons were used in Test 42 and the application temperature was 93*C. The
initial pH of the solution,' as tested, was 4.5. The Radiac Wash marginally outperformed the
basic solvents tested at 93*C, but still overall dissolution efficiency was less than 20%. No
additional proprietary or commercially available solvent systems were tested in this program.
6.5 Corrosion/Dissolution Tests
Limited corrosion testing was performed prior to going on to the process development
phase of this task (which will be presented in Section 8). This testing was performed with the
carbonate only solvent. Corrosion with the EDTA/carbonate system was expected to be higher
based on past experience with EDTA-based solvent systems (References 3 and 24). Based on
the data generated to date it was also expected that the dissolution behavior of the
EDTA/carbonate system and the carbonate alone system would be similar. Additional testing
with the EDTA/carbonate system was also planned for the process development phase of this
The purpose of the corrosion tests was two fold:
1. Determine corrosion rates of 1018 carbon steel, Nickel 200, and Monel 400 in the
candidate carbonate/H202 decontamination solvent.
2. Determine if the presence of the metal specimens adversely affected the uranium
dissolution performance of the solvent.
The first test with corrosion coupons (Test 64) used the carbonate only system with all
solvent constituents at their lowest tested concentration:
10 g/L (NH4)2CO3
2.5 g/L H202
pH 9.0
4 g/L UO2 Deposit Added To Test Flask
Room Temperature Application
The test duration was eight hours. Corrosion loss was low and uniform. The 1018 carbon steel
corrosion was 0.86 m (0.034 mils). This calculates to the very low corrosion rate of 0.11
m/hr. The corrosion loss on the Nickel 200 and Monel 400 were both 0.05 Ym (0.002 mils).
The surprising result from Test 64 was the low uranium oxide dissolution. Less than
60% of the UO2 added to the test flask was dissolved. Based on the previous testing 100%
dissolution was expected. The low corrosion rate of the coupons was not expected to affect the
overall UO2 dissolution effectiveness.
Closer examination of the data revealed rapid H202 depletion. Table 7 compares Test
64 H202 concentrations to the Test 59 H202 concentrations. Both tests used the same basic
solvent. Test 59 had a greater amount of deposit present (8 g/L UO2) but no corrosion coupons.
The Test 59 application resulted in essentially 100% deposit dissolution. From Table 7 it is
evident that very rapid H202 decomposition occurred during Test 64. It was theorized that the


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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. ( accessed May 22, 2019), University of North Texas Libraries, Digital Library,; crediting UNT Libraries Government Documents Department.

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