SLUDGE BATCH 5 SIMULANT FLOWSHEET STUDIES

[摘要] The Defense Waste Processing Facility (DWPF) will transition from Sludge Batch 4 (SB4) processing to Sludge Batch 5 (SB5) processing in early fiscal year 2009. Tests were conducted using non-radioactive simulants of the expected SB5 composition to determine the impact of varying the acid stoichiometry during the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME) processes. The work was conducted to meet the Technical Task Request (TTR) HLW/DWPF/TTR-2007-0007, Rev. 1 and followed the guidelines of a Task Technical and Quality Assurance Plan (TT&QAP). The flowsheet studies are performed to evaluate the potential chemical processing issues, hydrogen generation rates, and process slurry rheological properties as a function of acid stoichiometry. Initial SB5 flowsheet studies were conducted to guide decisions during the sludge batch preparation process. These studies were conducted with the estimated SB5 composition at the time of the study. The composition has changed slightly since these studies were completed due to changes in the washing plan to prepare SB5 and the estimated SB4 heel mass. Nine DWPF process simulations were completed in 4-L laboratory-scale equipment using both a batch simulant (Tank 51 simulant after washing is complete) and a blend simulant (Tank 40 simulant after Tank 51 transfer is complete). Each simulant had a set of four SRAT and SME simulations at varying acid stoichiometry levels (115%, 130%, 145% and 160%). One additional run was made using blend simulant at 130% acid that included additions of the Actinide Removal Process (ARP) waste prior to acid addition and the Modular Caustic Side Solvent Extraction (CSSX) Unit (MCU) waste following SRAT dewatering. There are several parameters that are noteworthy concerning SB5 sludge: (1) This is the first batch DWPF will be processing that contains sludge that has had a significant fraction of aluminum removed through aluminum dissolution. (2) The sludge is high in mercury. (3) The sludge is high in noble metals. (4) The sludge is high in U and Pu--components that are not added in sludge simulants. Two SB5 processing issues were noted during testing. First, high hydrogen generation rates were measured during experiments with both the blend and batch simulant at high acid stoichiometry. Also, the reflux time was extended due to the high mercury concentration in both the batch and blend simulant. Adding ARP will extend processing times in DWPF. The ARP caustic boil took approximately six hours. The boiling time during the experiment with added MCU was 14 hours at the maximum DWPF steam flux rate. This is comparable to the DWPF processing time for dewatering plus reflux without MCU at a 5000 lbs/hr boil-up rate, but would require significantly more time at boiling at 2000-2500 lbs/hr boil-up rate. The addition of ARP and MCU did not cause any other processing issues, since foaming, rheology and hydrogen generation were less of an issue while processing with ARP/MCU.

[发布日期] 2008-10-03

[学科分类] 核能源与工程

[关键词] AR FACILITIES;SLUDGES;RADIOACTIVE WASTE PROCESSING;FLOWSHEETS;CHEMICAL COMPOSITION;SIMULATION