Chelant screening and refinement tests - Phase I, Task 2. Topical progress report, December 1993--June 1994 Page: 25 of 236
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is a chemical cleaning industry standard for use with organic acids and chelating agents.
As can be seen from the data presented in Appendices B and C, corrosion loss was very
low in all cases and for all materials. Total corrosion ranged from a low of 0 (no detectable
weight loss) to a high of 0.0044 mils (0.11 m) on one of the carbon steel coupons. This value
of 0.0044 mils in eight (8) hours of exposure calculates to a very low corrosion rate of 4.8 mils
per year (equivalent to 0.01 m/hr). These results indicated that the inhibited solvent system
would likely meet the criteria of low controlled corrosion rates.
5.3 High Temperature (93*C) Uranium Dissolution Testing
Once the JSP was approved, the uranium dissolution phase of the testing commenced.
Each of the three candidate chelants (EDTA, HEDTA, DTPA) was initially tested, using the
standard Section 4 test procedure, at a pH of 7.0 and 9.0. EDTA was also tested at a pH of
5.5. These were designated Tests 7 through 13. Note that DTPA was also tested at an initial
pH of 5.0 (Test 17). All of these tests were performed at 93*C and utilized an inhibitor (again
Rodine 31A) concentration of 3 mL/L.
The results were similar for all of these tests; only a small amount of the uranium dioxide
added to the test flask (1 %-4%) dissolved, generally during the first few hours of exposure. The
UO2 solubility values reported in Appendix B tables were calculated from the weight of deposit
filtered from the spent solvent after testing. These values were adjusted for loss of deposit
removed during sampling and captured on Millipore filters during sample preparation. Corrosion
of the Mone) 400 and the Nickel 200 was negligible and equivalent to that of the solvents
without the UO2 added. The corrosion rate of the carbon steel increased slightly over the no-
deposit case. The rate appeared to increase as the initial pH of the solvent was lowered.
However, the highest carbon steel corrosion rate (Test 17 - DTPA/pH 5) in these tests was only
47 mils per year (mpy) or 0.14 gm/hr. This corrosion rate still met the acceptance criteria.
At this point the trials shifted to the proprietary ESI products (Tests 14, 15, and 16).
These tests utilized the ESI products in the as-received condition, as requested by ESI. ESI-600
was used in Test 14. This product had an initial pH of 6.8. The ESI-600 was reported by
Environmental Scientific to contain 5.9% chelant with no corrosion inhibitor. ESI-603X was
used in Test 15. This product had an initial pH of 10.7 The ESI-603X was reported by
Environmental Scientific to contain 7% chelant with no corrosion inhibitor. ESI-680 was used
in Test 16. This product was supplied as a powder. Per instructions, the powder was dissolved
in water. A temperature between 80*C and 90*C was required to dissolve the powder. The
ESI-680 also tended to crystallize if the temperature fell below 80*C. The final solution had
an initial pH of 4.7. The ESI-680 was reported to contain an inhibitor and 6% chelant. All of
the ESI tests were performed using the standard test procedure at an application temperature of
The results with the ESI products were similar to the earlier tests with EDTA, HEDTA,
and DTPA. Only a small amount of the uranium dioxide added to the test flask (1%-4%)
dissolved, generally during the first few hours of exposure. Corrosion was slightly higher with
the ESI products, especially for the carbon steels. The ESI-600 test (14) resulted in a carbon
steel corrosion rate of 507 mpy (1.5 m/hr). However, the criterion of uniform corrosion loss
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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/m1/25/: accessed April 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.