FAI has broad expertise in chemical issues that arise in decontamination and decommissioning (D&D) and nuclear waste technology.  In particular, we have decades of experience in performing research and development to support remediation of the U.S. Department of Energy nuclear facilities. Our Waste Technology department has provided process engineering and safety support through analyses, software development and experiments for a wide variety of nuclear-chemical engineering issues.

 Major project and facility applications related to spent fuel processing are:

• Idaho National Laboratory:  Technical basis for aluminum/grout chemical reactions and hydrogen flammability; Dust explosion technical basis for mixed-waste treatment
• K Basins Closure at Hanford, SNF Particulate: R&D, process development and software development for spent nuclear fuel particulate vacuum drying
• K Basins Closure at Hanford, SNF Sludge:  Process simulation for spent nuclear fuel sludge chemical/thermal treatment using FAI’s FATE^TM software
• Plutonium Finishing Plant, PFP/PRF at Hanford:  Aerosol release basis for litigation, experiments and analysis explaining the PRF explosion accident
• Spent Nuclear Fuel Project at Hanford:  Four of seven fundamental technical basis documents for passivation and storage of 2000 metric tons of damaged Uranium metal fuel; software for process safety, Uranium-metal reactions and pyrophoricity
• Spent Nuclear Fuel Sludge Project at Hanford:  Chemically reactive sludge property technical basis; radiolysis, flammable gas and process analyses
• Nuclear Waste Tanks at Savannah River and Hanford:  Adiabatic calorimetry and propagation tube experiments for chemically reactive waste; hydrogen mixing and solvent burning experiments; software for process safety
• Waste Encapsulation & Storage Facility at Hanford:  Technical basis for Strontium and Cesium capsule disposition
• Waste Treatment Plant at Hanford: Explosive hazards analysis; due diligence and management transition; flammable gas design guide
• Waste Receiving and Packaging Facility at Hanford:  Fire and source term analysis

Processing of sludge that contains heavy, gas-generating embedded particles presents unique difficulties.  In particular, such sludge has a high yield stress, so the gas generated inside a container of sludge cannot readily escape.  Rather than rise through the sludge, gas bubbles tend to coalesce within the sludge, potentially growing into a much larger mechanically stable bubble that can displace the overlying material.  This can have the unwanted consequence of plugging filters or even releasing sludge from the container.

Stable bubbles are clearly undesirable, so it is important to be able to predict bubble instability (breakup) and if necessary evaluate possible container design features that can disrupt or prevent the formation of stable bubbles.  FAI has extensive analytical and experimental experience in analyzing nuclear waste tank sludge.

FAI performed basic research and development on the stability of sludge gas bubbles, using Taylor stability theory to develop a criterion for sludge bubble breakup.  This predictive criterion was then validated by a series of experiments using various geometries and scales (see example illustrations below).  Specific design features related to the container wall were evaluated to demonstrate their effectiveness at preventing or disrupting bubble formation.