SLUDGE TREATMENT PROJECT KOP DISPOSITION - THERMAL AND GAS ANALYSIS FOR THE COLD VACUUM DRYING FACILITY

The purpose of this document is to present conceptual design phase thermal process calculations that support the process design and process safety basis for the cold vacuum drying of K Basin KOP material. This document is intended to demonstrate that the conceptual approach: (1) Represents a workable process design that is suitable for development in preliminary design; and (2) Will support formal safety documentation to be prepared during the definitive design phase to establish an acceptable safety basis. The Sludge Treatment Project (STP) is responsible for the disposition of Knock Out Pot (KOP) sludge within the 105-K West (KW) Basin. KOP sludge consists of size segregated material (primarily canister particulate) from the fuel and scrap cleaning process used in the Spent Nuclear Fuel process at K Basin. The KOP sludge will be pre-treated to remove fines and some of the constituents containing chemically bound water, after which it is referred to as KOP material. The KOP material will then be loaded into a Multi-Canister Overpack (MCO), dried at the Cold Vacuum Drying Facility (CVDF) and stored in the Canister Storage Building (CSB). This process is patterned after the successful drying of 2100 metric tons of spent fuel, and uses the same facilities and much of the same equipment that was used for drying fuel and scrap. Table ES-l present similarities and differences between KOP material and fuel and between MCOs loaded with these materials. The potential content of bound water bearing constituents limits the mass ofKOP material in an MCO load to a fraction of that in an MCO containing fuel and scrap; however, the small particle size of the KOP material causes the surface area to be significantly higher. This relatively large reactive surface area represents an input to the KOP thermal calculations that is significantly different from the calculations for fuel MCOs. The conceptual design provides for a copper insert block that limits the volume available to receive KOP material, enhances heat conduction, and functions as a heat source and sink during drying operations. This use of the copper insert represents a significant change to the thermal model compared to that used for the fuel calculations. A number of cases were run representing a spectrum of normal and upset conditions for the drying process. Dozens of cases have been run on cold vacuum drying of fuel MCOs. Analysis of these previous calculations identified four cases that provide a solid basis for judgments on the behavior of MCO in drying operations. These four cases are: (1) Normal Process; (2) Degraded vacuum pumping; (3) Open MCO with loss of annulus water; and (4) Cool down after vacuum drying. The four cases were run for two sets of input parameters for KOP MCOs: (1) a set of parameters drawn from safety basis values from the technical data book and (2) a sensitivity set using parameters selected to evaluate the impact of lower void volume and smaller particle size on MCO behavior. Results of the calculations for the drying phase cases are shown in Table ES-2. Cases using data book safety basis values showed dry out in 9.7 hours and heat rejection sufficient to hold temperature rise to less than 25 C. Sensitivity cases which included unrealistically small particle sizes and corresponding high reactive surface area showed higher temperature increases that were limited by water consumption. In this document and in the attachment (Apthorpe, R. and M.G. Plys, 2010) cases using Technical Databook safety basis values are referred to as nominal cases. In future calculations such cases will be called safety basis cases. Also in these documents cases using parameters that are less favorable to acceptable performance than databook safety values are referred to as safety cases. In future calculations such cases will be called sensitivity cases or sensitivity evaluations Calculations to be performed in support of the detailed design and formal safety basis documentation will expand the calculations presented in this document to include: additional features of the drying cycle, more realistic treatment of uranium metal consumption during oxidation, larger water inventory, longer time scales, and graphing of results of hydrogen gas concentration