Large area decontamination after a radiological incident.

Effective decontamination of large-scale areas such as roads and parking lots after an accidental or intentional radiological incident is important in order to contain the spread of contamination and avoid the need for long-term evacuation of urban areas. As a simulation, large coupons (surface area 3600 cm2) made of concrete patio stone and aged asphalt (from a parking lot) were contaminated with either 60Co or 137Cs solutions and then decontaminated. The decontamination process consisted of a six-component water-based chemical formulation applied using a common house-hold carpet cleaner. Tests were carried out to compare the effectiveness of decontamination using deionized water (simulating rain fall) and chemical formulation. Test results showed that rain fall prior to decontamination lowered the effectiveness of a subsequent decontamination regardless of the surface type or radionuclide. Tests were also carried out to determine if the decontamination effectiveness increased with multiple applications. Using multiple applications of the chemical formulation, the removal of 60Co from concrete patio stone and aged asphalt were 65 ±â€¯2% and 70 ±â€¯3%, respectively, while the removal of 137Cs was 53 ±â€¯3% from asphalt surfaces and 21 ±â€¯8% from concrete patio stone. This paper summarizes the work carried out to prepare for the tests, presents the test results and compares the process to several other processes in terms of effectiveness and suitability for application on a large scale.

Decontamination of select infrastructure materials after a radiological incident using a water-based formulation.

This paper summarizes the results of the decontamination of the infrastructure materials concrete, limestone, brick and asphalt contaminated with 60Co, 85Sr, 137Cs and 241Am. The paper focuses on the effect of differences in substrate properties and of the pH of the radionuclide solution used for surface contamination on adsorption or ion exchange of the radionuclides and how these factors affect the decontamination effectiveness. A six-component chemical formulation was used and a process effectiveness of up to 76% was obtained depending on the substrate and radionuclide. Asphalt was the easiest material to decontaminate because of its more hydrophobic nature. Concrete and limestone (and to some extent brick) were less effectively decontaminated as their porous surfaces allowed penetration of radionuclides into water-filled pores in the substrate facilitating adsorption or ion exchange and making them difficult to remove. Brick was the most difficult material to decontaminate because the major component of brick is clay which retains most mono- and divalent ions. The removal of 60Co, 85Sr and 137Cs from the surfaces of concrete, limestone and brick increased when the pH of the radionuclide solutions was moderately acidic to neutral compared to when they were highly acidic. The variability in the test results was similar to that observed in other studies using other decontamination methods, attributed to the inhomogeneity of the substrates used and considered representative of real infrastructure materials.