Treatability Studies and Large-Scale Treatment of Aqueous Mixed Waste Containing Heavy Metals

Wastes have accumulated at the Idaho National Engineering Laboratory through routine laboratory practices, experimental engineering operations, and decommissioning and decontamination of nuclear reactor facilities. A storage tank at the Test Area North held approximately 129,000 L of acidic wastewater and contained prohibited levels of lead and mercury. Radioactive constituents were also present; the most predominant being radiocesium Cs-137 and radiocobalt Co-60. Bench-scale studio were undertaken to evaluate ion exchange as a means of removing the contaminants. A set of breakthrough curves was obtained and identified capacity constraints, selectivities, and operating requirements of candidate resins. Treatment studies indicated that Purolite S-920 resin could effectively remove mercury, while Rohm and Haas` Amberlite 200-CH was used for lead and radionuclide removal. Based on these laboratory tests a full-scale facility, using multiple ion exchange columns, was designed and operated in the spring of 1994. The liquid effluents were discharged to an onsite evaporation pond and met RCRA disposal limits for hazardous metals and self-imposed radionuclide limits. All secondary wastes and residues were sampled and subjected to the to)dc characteristic leaching procedure. The resulting leachate concentrations were below RCRA discharge limits and, therefore, these will be disposed of at the onsite low-level disposal facility. After concluding the tank wastewater operations, enough reserve resin capacity was available to treat three additional mixed wastes residing onsite. These totaled about 1,900 L (500 gal) and contained prohibited levels of chromium, cadmium, and barium. Laboratory studies demonstrated that these heavy metals could also be removed by the existing resins. Treatment was performed at the full-scale facility with the effluents discharged to the evaporation pond

Summary of FY 2010 Iodine Capture Studies at the INL

Three breakthrough runs using silver mordenite sorbents were conducted and a dynamic sorption capacity estimated based on MeI analysis from a 2" bed. However, it is now believed the data for the first 2 runs is incomplete because the contributions from elemental iodine were not included. Although the only source of iodine was MeI, elemental iodine was generated within the sorbent bed, presumably from a recombination reaction likely catalyzed by silver mordenite. On-line effluent analysis with a GC was only capable of analyzing MeI, not I2. Scrub samples drawn during Run #3, which are specific for I2, show significant levels of I2 being emitted from a partially spent Ag-mordenite bed. By combining MeI and I2 analyses, a well defined total iodine breakthrough curve can be generated for Run #3. At the conclusion of Run #3 (IONEX Ag-900 was the sorbent) the effluent level from Bed 2 was approaching 70% of the feed concentration. The leading bed (Bed 1) had an estimated average loading of 66 mg I/g sorbent, Bed 2's was 52 mg I/g. The corresponding silver utilizations (assuming formation of AgI) were about 59% and 46%, respectively. The spent sorbents are being sent to Sandia National Laboratories for confirmatory analysis of iodine and silver utilization as well as source material for waste form development

Survey of Dynamic Simulation Programs for Nuclear Fuel Reprocessing

The absence of any industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other industries. Modeling programs to simulate the dynamic behavior of nuclear fuel separations and processing were originally developed to support the US government’s mission of weapons production and defense fuel recovery. Consequently there has been little effort is the US devoted towards improving this specific process simulation capability during the last two or three decades. More recent work has been focused on elucidating chemical thermodynamics and developing better models of predicting equilibrium in actinide solvent extraction systems. These equilibrium models have been used to augment flowsheet development and testing primarily at laboratory scales. The development of more robust and complete process models has not kept pace with the vast improvements in computational power and user interface and is significantly behind simulation capability in other chemical processing and separation fields

Summary of FY 2010 Iodine Capture Studies at the INL

Three breakthrough runs using silver mordenite sorbents were conducted and a dynamic sorption capacity estimated based on MeI analysis from a 2" bed. However, it is now believed the data for the first 2 runs is incomplete because the contributions from elemental iodine were not included. Although the only source of iodine was MeI, elemental iodine was generated within the sorbent bed, presumably from a recombination reaction likely catalyzed by silver mordenite. On-line effluent analysis with a GC was only capable of analyzing MeI, not I2. Scrub samples drawn during Run #3, which are specific for I2, show significant levels of I2 being emitted from a partially spent Ag-mordenite bed. By combining MeI and I2 analyses, a well defined total iodine breakthrough curve can be generated for Run #3. At the conclusion of Run #3 (IONEX Ag-900 was the sorbent) the effluent level from Bed 2 was approaching 70% of the feed concentration. The leading bed (Bed 1) had an estimated average loading of 66 mg I/g sorbent, Bed 2's was 52 mg I/g. The corresponding silver utilizations (assuming formation of AgI) were about 59% and 46%, respectively. The spent sorbents are being sent to Sandia National Laboratories for confirmatory analysis of iodine and silver utilization as well as source material for waste form development

System Design Description and Requirements for Modeling the Off-Gas Systems for Fuel Recycling Facilities

This document provides descriptions of the off-gases evolved during spent nuclear fuel processing and the systems used to capture the gases of concern. Two reprocessing techniques are discussed, namely aqueous separations and electrochemical (pyrochemical) processing. The unit operations associated with each process are described in enough detail so that computer models to mimic their behavior can be developed. The document also lists the general requirements for the desired computer models