Pilot Scale Advanced Fogging Demonstration
Radiological contamination control is crucial during decommissioning and demolition (D&D) activities, as well as during modifications to existing radiological systems. It is well known that contamination, in some cases substantial contamination, is present throughout the exhaust ductwork in several older processing facilities within the Department of Energy (DOE) complex, due to years of processing radioactive materials in areas served by closed ventilation systems. Accumulations of radioactive dust and lint – commonly found in laundry facilities, exhaust ventilation ducting, and exhaust stacks – present a specific contamination control issue. Particle suspension is more likely to occur during cleaning, modification, or demolition of these systems and during disposal site exhumation. In a recent demolition of large ventilation ducting (~10’ × 10’ cross section, ~100’ long) at Brookhaven National Laboratory, a spray coating was manually applied to the inside of the duct – requiring painters, dressed in anti-contamination clothing and an airline respirator system, to enter the duct.1 The advanced fogging technique offers an alternative method to mitigate these airborne contamination hazards with minimal personnel entry. Experiments in 2006 developed a useful fog solution using three different chemical constituents. Optimization of the fog recipe and use of commercially available equipment were identified as needs that had not been addressed. During 2012 development work it was noted that low concentrations of the components hampered coverage and drying in the United Kingdom’s National Nuclear Laboratory’s testing much more so than was evident in the 2006 tests. In fiscal year 2014 the Idaho National Laboratory undertook a systematic optimization of the fogging formulation and conducted a non-radioactive, pilot scale demonstration using commercially available fogging equipment. While not as sophisticated as the equipment used in earlier testing, the new approach is much less expensive and readily available for smaller scale operations. Pilot scale testing was important to validate new equipment of an appropriate scale, optimize the chemistry of the fogging solution, and to realize the conceptual approach.