The Defense Waste Processing Facility (DWPF) air lift pump was successfully tested at Clemson for 72 days of operation. It provided sufficient flow to pump molten glass without excessive foaming. Slurry feeding also did not reveal any problems with cold cap stability. Metallurgically the Inconel 690 (690) portions of the pump were in excellent condition with no visual evidence of degradation even in high flow regions, i.e., air/melt interface and glass discharge regions. Spinel deposits, which completely covered the air passage on one side, were found at the inlet of each platinum/rhodium (Pt/Rh) nozzle. Although the deposits were extensive, they were porous and did not have an adverse effect on the operation of the pump. The technique used to secure the platinum/rhodium nozzles to the 690 housing appeared to be adequate with only minor oxidation of the 690 threads and glass in-leakage. Galvanic attack was observed where the nozzle formed a seal with the 690. Significant pitting of the 690 was observed around the entire seal. Intergranular cracking of the Pt/Rh alloy was extensive but the cause could not be determined. Testing would be required to evaluate the degradation. Data from the performance test and the metallurgical evaluation are being used to modify the design of the first DWPF production air lift pump. It will be fabricated entirely from 690 and use argon as the purge gas. It is intended to have a service life of 6 months. Recommendations for insertion, operation, and inspection of the pump are also included in this report. Performance data collected from the operation of the production pump will be used to further optimize the design. Laboratory exposure tests should also be performed to evaluate the galvanic effect between platinum/rhodium and 690. Due to the success of these tests and modeling work, a full-scale Inconel unit was fabricated and installed in a glass hold tank at the Clemson Environmental Technologies Laboratory (CETL) facility on September 30, 2002. The main purpose of this test was to evaluate the expected unit life. To the extent possible, the test was performed to also provide information on air lift design details and foam collapse rate. Design details of glass discharge height and nozzle design were also tested, as they require full scale testing in molten glass. This report discusses the full scale air lift pump tests at the CETL. This includes the non-destructive and destructive evaluations (NDE and DE) performed on the pump after the test.
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