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 ± 2% and 70 ± 3%, respectively, while the removal of 137Cs was 53 ± 3% from asphalt surfaces and 21 ± 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.