Transuranic Liquid Waste Treatment Demonstration Conceptual Design

Project Synopsis

Project Summary

Process Engineering Associates, LLC (PROCESS) was contracted to perform a conceptual process design for the TRU Liquid Waste Treatment Demonstration project (TRU-LWTD).  The client produces isotopes for research, medical, and industrial applications, and as a result of these operations generates high level transuranic radioactive waste.  This waste is currently processed through existing disposal paths, but these disposal paths will be decommissioned after completion of legacy waste processing.  New treatment capabilities will be required to characterize, treat, concentrate, package, and certify the high-level waste generated by the isotope program.

The TRU-LWTD system will segregate incoming waste according to source and type, evaporate the water from the waste to either a target specific gravity or a maximum contact dose, characterize the concentrated waste, and mix the concentrate with grout in drums for solidification before ultimate disposal.  The organic fraction in the feed stream is separated from the aqueous and solidified with grout without additional processing.  Condensate is collected and characterized for ultimate disposal.  The entire process will be installed in a hot cell and all operations performed remotely.

Specific tasks for this project included:

• Preparation of mass and energy balances for multiple cases of the two main feed waste streams. Raw waste stream data were used as inputs to calculate an overall mass and energy balance of the semi-batch operation involving mixing, transfers, evaporation, cooling, and condensation.  Individual step and overall processing times were calculated for waste batches received from the waste generating facility.  CHEMCAD licensed process simulation software and OLI electrolyte simulation software were utilized to predict stream temperature, density, viscosity, boiling point, pH, composition, electrolyte reactions, complex salt solution solubility, and species and amount of salt that precipitate from the waste streams under varying input concentrations and degree of evaporation.  Utility usage was also calculated.
• Development of eight (8) Process Flow Diagrams (PFDs) depicting the TRU-LWTD system.
• Development of twenty-two (22) Piping & Instrumentation Diagrams (P&IDs) for the TRU-LWTD system. These P&IDS included all major equipment items, process and utility streams, and primary instruments and controls.
• Preliminary design of evaporators, including heat transfer surface and internals required to achieve desired boilup rate, volume reduction factor (VRF), decontamination factor (DF), and foaming control. As part of this preliminary design, a literature search was performed to identify defendable sizing parameters to achieve the desired process goals based on the actual performance of evaporators processing similar waste streams.
• Preliminary sizing of process vessels including vessels, evaporators, heat exchangers, and scrubber. Sizing and design also considered the limited space available in the hot cell and the need to maintain the system using remote manipulators.
• Preliminary sizing of process lines. As part of this sizing, a literature search was performed to identify a suitable sizing methodology for lines that will handle salt solutions containing solids.  Equations developed by multiple sources to determine the critical velocity based on solution properties and solids content were used to calculate a minimum velocity.
• Performance of literature searches to determine design parameters for air mixing systems to be used in the vessels based on agitation in systems that process similar waste streams. Due to the remote handled nature of the process and the high radiation dose, it is desired to avoid mechanical agitation devices.
• Participation in internal and external design reviews.

The project tasks were completed under budget and on a schedule that fully supported the project team’s other tasks and goals.

Industry Type

• Nuclear Materials Production
• Nuclear Waste Processing

Utilized Skills

• Conceptual process design
• Complex materials characterization
• Nuclear materials handling