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Title: ALTERNATE REDUCTANT COLD CAP EVALUATION FURNACE PHASE I TESTING

Savannah River Remediation (SRR) conducted a Systems Engineering Evaluation (SEE) to determine the optimum alternate reductant flowsheet for the Defense Waste Processing Facility (DWPF). Specifically, two proposed flowsheets (nitric–formic–glycolic and nitric–formic–sugar) were evaluated based upon results from preliminary testing. Comparison of the two flowsheets among evaluation criteria indicated a preference towards the nitric–formic–glycolic flowsheet. Further evaluation of this flowsheet eliminated the formic acid1, and as a result, the nitric–glycolic flowsheet was recommended for further testing. Based on the development of a roadmap for the nitric–glycolic acid flowsheet, Waste Solidification Engineering (WS-E) issued a Technical Task Request (TTR) to address flammability issues that may impact the implementation of this flowsheet. Melter testing was requested in order to define the DWPF flammability envelope for the nitric glycolic acid flowsheet. The Savannah River National Laboratory (SRNL) Cold Cap Evaluation Furnace (CEF), a 1/12th scale DWPF melter, was selected by the SRR Alternate Reductant project team as the melter platform for this testing. The overall scope was divided into the following sub-tasks as discussed in the Task Technical and Quality Assurance Plan (TTQAP): Phase I - A nitric–formic acid flowsheet melter test (unbubbled) to baseline the Cold Cap Evaluation Furnace (CEF) cold cap andmore » vapor space data to the benchmark melter flammability models Phase II - A nitric–glycolic acid flowsheet melter test (unbubbled and bubbled) to: o Define new cold cap reactions and global kinetic parameters for the melter flammability models o Quantify off-gas surging potential of the feed o Characterize off-gas condensate for complete organic and inorganic carbon species Prior to startup, a number of improvements and modifications were made to the CEF, including addition of cameras, vessel support temperature measurement, and a heating element near the pour tube. After charging the CEF with cullet from a previous Sludge Batch 6 (SB6) run, the melter was slurry-fed with SB6-Frit 418 melter feed at 36% waste loading and was operated continuously for 6 days. Process data was collected throughout testing and included melter operation variables and off-gas chemistry. In order to satisfy the objective of Phase I testing, vapor space steady testing in the range of ~300°C-700°C was conducted without argon bubbling to baseline the melter data to the existing DWPF melter flammability model. Adjustments to heater outputs, air flows and feed rate were necessary in order to achieve the vapor space temperatures in this range. The results of the Phase I testing demonstrated that the CEF is capable of operating under the low vapor space temperatures A melter pressure of -5 inches of water was not sustained throughout the run, but the melter did remain slightly negative even with the maximum air flows required for the lowest temperature conditions were used. The auxiliary pour tube heater improved the pouring behavior at all test conditions, including reduced feed rates required for the low vapor space testing. Argon bubbling can be used to promote mixing and increase feed rate at multiple conditions. Improvements due to bubbling have been determined previously; however, the addition of the cameras to the CEF allows for visual observation during a range of bubbling configurations. The off-gas analysis system proved to be robust and capable of operating for long durations. The total operational hours on the melter vessel are approximately 385 hours. Dimensional measurements taken prior to Phase I testing and support block temperatures recorded during Phase I testing are available if an extension of service life beyond 1250 hours is desired in the future.« less
Authors:
; ; ;
Publication Date:
OSTI Identifier:
1130786
Report Number(s):
SRNL-STI-2014-00005
DOE Contract Number:
DE-AC09-08SR22470
Resource Type:
Technical Report
Research Org:
SRS
Sponsoring Org:
DOE
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES alternate reductant, cold cap evaluation furnace (CEF)