Follow-up testing was conducted to better understand the excessive hydrogen generation seen in the initial Sludge Batch 4 (SB4) qualification Sludge Receipt and Adjustment Tank/Slurry Mix Evaporator (SRAT/SME) simulation in the Savannah River National Laboratory (SRNL) Shielded Cells. This effort included both radioactive and simulant work. The initial SB4 qualification test produced 0.59 lbs/hr hydrogen in the SRAT, which was just below the DWPF SRAT limit of 0.65 lbs/hr, and the test produced over 0.5 lbs/hr hydrogen in the SME cycle on two separate occasions, which were over the DWPF SME limit of 0.223 lbs/hr. A fresh sample of Tank Farm washed Tank 51 slurry was obtained to perform a duplicate test under the same conditions used in the initial SB4 qualification SRAT/SME simulation. Extensive analysis of the sludge as well as SRAT and SME products was performed, but the acid addition strategy (i.e., total moles of acid added per liter of slurry) for the SRAT cycle was not varied due to any small changes in measured quantities in the input to the stoichiometric acid calculation. A new SB4 simulant was prepared in parallel with the radioactive work. This simulant was a very close match to the measured composition of the slurry used in the initial qualification test. A portion of this simulant was subjected to a heat-treatment intended to qualitatively simulate what happened to a portion of the radioactive material used in the SB4 qualification test. The main purpose of the simulant tests was to determine whether or not subjecting some of the SRAT feed to a heat-treatment would cause a significant difference in the observed hydrogen generation rates during SRAT/SME processing.
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