Assessment of the Use of Nitrogen Trifluoride for Purifying Coolant and Heat Transfer Salts in the Fluoride Salt-Cooled High-Temperature Reactor

This report provides an assessment of the use of nitrogen trifluoride for removing oxide and water-caused contaminants in the fluoride salts that will be used as coolants in a molten salt cooled reactor

Scale-Up, Production, and Procurement of PEP Simulants

Pacific Northwest National Laboratory has been tasked by Bechtel National Inc. on the River Protection Project-Hanford Tank Waste Treatment and Immobilization Plant (RPP-WTP) project to perform research and development activities to resolve technical issues identified for the Pretreatment Facility. The Pretreatment Engineering Platform (PEP) was designed, constructed, and operated as part of a plan to respond to issue M12, “Undemonstrated Leaching Processes.” The PEP is a 1/4.5-scale test platform designed to simulate the WTP pretreatment caustic leaching, oxidative leaching, ultrafiltration solids concentration, and slurry washing processes. The PEP replicates the WTP leaching processes using prototypic equipment and control strategies. This report provides the lessons learned regarding the manufacture and delivery of simulated feeds for PEP testing

Thermal Flammable Gas Production from Bulk Vitrification Feed

The baseline bulk-vitrification (BV) process (also known as in-container vitrification ICV™) includes a mixer/dryer to convert liquid low-activity waste (LAW) into a dried, blended feed for vitrification. Feed preparation includes blending LAW with glass-forming minerals (GFMs) and cellulose and drying the mixture to a suitable dryness, consistency, and particle size for transport to the ICVTM container. The cellulose is to be added to the BV feed at a rate sufficient to destroy 75% of the nitrogen present as nitrate or nitrite. Concern exists that flammable gases may be produced during drying operations at levels that could pose a risk. The drying process is conducted under vacuum in the temperature range of 60 to 80°C. These flammable gases could be produced either through thermal decomposition of cellulose or waste organics or as a by-product of the reaction of cellulose and/or waste organics with nitrate or the postulated small amount of nitrite present in the waste. To help address the concern about flammable gas production during drying, the Pacific Northwest National Laboratory (PNNL) performed studies to identify the gases produced at dryer temperatures and at possible process upset conditions. Studies used a thermogravimetric analyzer (TGA) up to 525°C and isothermal testing up to 120°C to determine flammable gas production resulting from the cellulose and organic constituents in bulk vitrification feed. This report provides the results of those studies to determine the effects of cellulose and waste organics on flammable gas evolutio

Nitrogen Trifluoride-Based Fluoride- Volatility Separations Process: Initial Studies

This document describes the results of our investigations on the potential use of nitrogen trifluoride as the fluorinating and oxidizing agent in fluoride volatility-based used nuclear fuel reprocessing. The conceptual process uses differences in reaction temperatures between nitrogen trifluoride and fuel constituents that produce volatile fluorides to achieve separations and recover valuable constituents. We provide results from our thermodynamic evaluations, thermo-analytical experiments, kinetic models, and provide a preliminary process flowsheet. The evaluations found that nitrogen trifluoride can effectively produce volatile fluorides at different temperatures dependent on the fuel constituent

The Status of Radiation Damage Experiments

Experiments have been on-going for about two years to determine the effects that radiation damage have on the physical and chemical properties of candidate titanate ceramics for the immobilization of plutonium. We summarize the results of these experiments in this document

Thermal Behavior of As-Recovered (Unneutralized) Aspigel (Pressure Measurements)

This brief report provides unreported pressures measured in accelerating rate calorimeter experiments performed to determine the thermal sensitivity of as-recovered and unneutralized Aspigel

Assessment of the Use of Nitrogen Trifluoride for Purifying Coolant and Heat Transfer Salts in the Fluoride Salt-Cooled High-Temperature Reactor

This report provides an assessment of the use of nitrogen trifluoride for removing oxide and water-caused contaminants in the fluoride salts that will be used as coolants in a molten salt cooled reactor

Characterization of the kinetics of NF3-fluorination of NpO2

Solid NpO2 has been contacted by gaseous NF3 under isothermal conditions at 450°C, 475°C, and 500°C; and the resulting reactions have been monitored using thermogravimetric analysis. In each case, at least two sequential reactions are clearly observed. The first reaction is fluorination of NpO2 to NpF4 and the second is oxidation and fluorination of NpF4 to NpF6. Careful observation of the experimental reaction curves reveals evidence of several physical and chemical mechanisms occurring sequentially and at times simultaneously. As such, a mathematical modeling approach utilizing a combination of sequential and parallel fundamental gas-solid reaction mechanisms (chemical reaction, diffusion, and phase boundary) is, in general, found to provide representative reaction curves that are in good agreement with experimental reaction curves. The correspondence of fundamental reaction mechanisms with distinctive characteristics of the experimental reaction curves (maximums and inflection points) provides insight into the physical and chemical nature of each reaction being monitored

Nitrogen Trifluoride-Based Fluoride- Volatility Separations Process: Initial Studies

This document describes the results of our investigations on the potential use of nitrogen trifluoride as the fluorinating and oxidizing agent in fluoride volatility-based used nuclear fuel reprocessing. The conceptual process uses differences in reaction temperatures between nitrogen trifluoride and fuel constituents that produce volatile fluorides to achieve separations and recover valuable constituents. We provide results from our thermodynamic evaluations, thermo-analytical experiments, kinetic models, and provide a preliminary process flowsheet. The evaluations found that nitrogen trifluoride can effectively produce volatile fluorides at different temperatures dependent on the fuel constituent

Use of Nitrogen Trifluoride To Purify Molten Salt Reactor Coolant and Heat Transfer Fluoride Salts

The molten-salt-cooled nuclear reactor is one of the Generation IV reactor types. One of the challenges of implementing this reactor is purifying and maintaining the purity of the various molten fluoride salts that will be used as coolants. The method used for Oak Ridge National Laboratory’s molten salt experimental test reactor was to treat the coolant with a mixture of H₂ and HF at 600 °C. In this Article, we evaluate thermal NF₃ treatment for purifying molten fluoride salt coolant candidates based on nitrogen trifluoride’s (1) past use to purify fluoride salts; (2) other industrial uses; (3) commercial availability; (4) operational, chemical, and health hazards; (5) environmental effects and environmental risk management methods; (6) corrosive properties; (7) thermodynamic potential to eliminate impurities that could arise due to exposure to water and oxygen. Our evaluation indicates that nitrogen trifluoride is a viable and safer alternative to the previous method