Part 2: Stabilization/Containment of Radiological Particle Contamination to Enhance First Responder, Early Phase Worker, and Public Safety

The application of stabilization technologies to a radiologically contaminated surface has the potential for reducing the spread of contamination and, as a result, decreasing worker exposure to radiation. Three stabilization technologies, calcium chloride (CaCl2), flame retardant Phos-Chek® MVP-Fx, and Soil2O™ were investigated to evaluate their ability to reduce the resuspension and tracking of radiological contamination during response activities such as vehicle and foot traffic. Concrete pavers, asphalt pavers, and sandy soil walking paths were used as test surfaces, along with simulated fallout material (SFM) tagged with radiostrontium (Sr-85) applied as the contaminant. Radiological activities were measured using gamma spectrometry before and after simulated vehicle operation and foot traffic experiments, conducted with each stabilization technology and without application as a nonstabilized control. These measurements were acquired separately for each combination of surface and vehicle/foot traffic experiment. The resulting data describes the extent of SFM removed from each surface onto the tires or boots, the extent of SFM transferred to adjacent surfaces, and the residual SFM remaining on the tires or boots after each experiment. The type of surface and response worker actions influenced the stabilization results. For instance, when walked over, less than 2% of particles were removed from nonstabilized concrete, 4% from asphalt, and 40% of the particles were removed from the sand surface. By contrast, for vehicle experiments, ~40% of particles were again removed from the sand, but 7% and 15% from concrete and asphalt, respectively. In most cases, the stabilization technologies did provide improved stabilization. The improvement was related to the type of surface, worker actions, and stabilizer; a statistical analysis of these variables is presented. Overall, the results suggest an ability to utilize these technologies during the planning and implementation of response activities involving foot and vehicle traffic. In addition, resuspension of aerosolizable range SFM was monitored during walking path foot traffic experiments, and all stabilizing agents decreased the measured radioactivity, with the Soil2O™ decrease being 3 fold, whereas the CaCl2 and Phos-Chek MVP-Fx surfaces generated no detectable radioactivity. Overall, these results suggest that the stabilization technologies decrease the availability of particles respirable by response workers under these conditions.


Application
CaCl2 was prepared as a dilute aqueous solution (with a viscosity similar to water) and applied using a 2-gallon garden sprayer as described above.The aqueous solution was applied gently not to disturb the particles on the surface until the particles were fully wetted, but before pooling on the surface occurred.The stabilization technologies were allowed to dry to the touch (at least overnight; 2-3 days for asphalt) before experiments were performed.

Surface interactions
Asphalt: CaCl2 was applied as described above and as the surfaces dried, the contaminated particles did not always dry to a lighter color compared to when they were wetted.Some of the contaminated particles maintained a darker color although they were wet, while some of the contaminated particles had a color change in line with what would be expected from observing drying soil.For example, in the photograph below, all four coupons had been treated with CaCl 2 and dried for the same amount of time, but obviously they looked very different from one another.
This phenomenon made it difficult to be certain that the surfaces were dry since they maintained a wetted appearance; the cause is still not clear.Two possible reasons are air flow patterns in the tent causing different rates of drying or chemical interactions with chemical constituents of the asphalt paver being drawn up into the CaCl2.After 2 to 3 days, the paver surface was touched with a paper towel to confirm dryness and thereafter the experiments were performed.

Concrete:
CaCl 2 was applied as described above, and it dried to the touch overnight with no other notable observations (see photograph at left below).
Soil: CaCl 2 was applied as described above, and it dried to the touch overnight with no other notable observations (see photograph at right above).During the walking path experiment, the CaCl2 formed a crust on the soil after drying.This crust tended to bind to the boot during walking and did not release until the walker reached the nonsoil surface.

Health and safety concerns
CaCl2 is stable under normal conditions of use and storage.While use directly in the environment should be evaluated carefully, according to the Safety Data Sheet (SDS), the product is minimally toxic and, upon disposal, is not a hazardous waste according to the Resource Conservation and Recovery Act.Cost $ 1 .4 5 / k g of CaCl2 pellets, which was equivalent to $1.50/m 2 of testing surface.

Parameters Operational Information
Application MVP-Fx was prepared as an aqueous solution (with a viscosity and red color similar to tomato juice -slightly more viscous than water) and applied using a 0.5-gallon handheld garden sprayer as described above.The 2-gallon sprayer used for the other two stabilization technologies would clog when using MVP-Fx.No clog was observed using a 0.5-gallon handheld garden sprayer for MVP-Fx due to different size of orifices for the nozzles.The aqueous solution was applied gently not to disturb the particles on the surface until the particles were fully covered with solution.Likely because of the viscosity of the solution, pooling on the surface occurred during application.The stabilization technologies were allowed to dry until dry to the touch (2-3 days) before experiments were performed.

Surface interactions
Asphalt: MVP-Fx was applied as described above, and it dried to the touch within 2-3 days.As it dried, MVP-Fx seemed to remain pooled on the surface of the asphalt and particles, creating a thicker red coating (in comparison to concrete and soil) on the surface when dry (see photograph at left below).
Concrete: MVP-Fx was applied as described above, and it dried to the touch within 2-3 days.As it dried, MVP-Fx seemed to penetrate exposed areas of concrete surface and sorb to surface particles resulting in a light red color on the surface (see center photograph above).
Soil: MVP-Fx was applied as described above, and it dried to the touch within 2-3 days.
As it dried, MVP-Fx seemed to penetrate the soil and contaminated particles resulting in a very light red color on the soil surface (see photograph at right above).

Health and safety concerns
Phos-chek MVP-Fx is a fire retardant used for wildland fire control.It is stable under normal conditions.The SDS for Phos-Chek MVP-Fx shows that it may cause long-term adverse effects in the aquatic environment, in general, the product seems to be minimally toxic.There is minimal disposal guidance in the SDS.Cost $6.80/kg of MVP-Fx, which was equivalent to $5/m 2 of testing surface.

Application
Soil2O was prepared as a dilute aqueous solution (with a viscosity similar to water) and applied using a 2-gallon garden sprayer as described above.The aqueous solution was applied gently not to disturb the particles on the surface until the particles were fully wetted but before pooling on the surface occurred.The stabilization technologies were allowed to dry until dry to the touch (at least overnight) before experiments were performed.

Surface interactions
Soil2O was applied to asphalt, concrete, and soil and it dried to the touch overnight with no other notable observations (see photographs below).

Health and safety concerns
Soil 2 O TM is a dust control agent.It is stable under normal conditions.According to the SDS, it seems to be a minimally toxic product that has been shown to generate no negative or toxic effects on the environment when released in dilution for terrestrial and aquatic ecosystems.It is a nonhazardous waste material suitable for approved solid waste landfills, as it is has demonstrated to be immobile in landfills and soil systems.Cost $3.47/kg of Soil 2 O, which was equivalent to $0.28/m 2 of testing surface.