a www.epa.gov/nhsrc Removing Radiological Contamination From Concrete Using Strippable Coatings Two technologies evaluated for their ability to remove cesium-137 contamination A radiological attack or dirty bomb detonation might require a massive, long-term evacuation to protect human health. This could greatly interfere with economic and business activities. As a result, there is much interest in technologies that can be and help with the cleanup. The U .S. Environmental Protection Agency evaluated two strippable coating technologies for their abilities to remove cesium-137 (Cs-137) from concrete surfaces: • Stripcoat TLC Free™ (Bartlett Services Inc.). which apparently binds radiological material only through physical interaction between the radiological material and the cured coating • Orion|M Strippable Coating (Orion™ SC) (Isotron Corp.), which apparently binds radiological material through chemical and physical interactions when it is cured ;ed to mitigate the potential damage U.S. EPA's Homeland Security Research Program (HSRP) develops products based on scientific research and technology evaluations. Our products and expertise are widely used in preventing, preparing for, and recovering from public health and environmental emergencies that arise from terrorist attacks. Our research and products address biological, radiological, or chemical contaminants that could affect indoor areas, outdoor areas, or water infrastructure. HSRP provides these products, technical assistance, and expertise to support EPA's roles and responsibilities under the National Response Framework, statutory requirements, and Homeland Security Presidential Directives. The treated surfaces were allowed to cure overnight into a solid coating. The coatings were removed from the concrete surfaces of the 7-day or 30-day cured coupons based on the manufacturers' directions. The technologies were evaluated for decontamination efficacy; labor costs and requirements; ease of use on irregular surfaces; surface damage; application and removal times; portability and secondary waste generation; utility Figure 1. Applying the Coating With a Sprayer requirements; and preparation and cleanup effort. October 2008 EPA/660/S-08/021 Concrete test coupons were contaminated with Cs-137 and aged for 7 or 30 days. The 7-day and 30-day tests were performed to determine if a rapid response would provide better decontamination efficacy. Figure 1 shows application with a paint sprayer, the method used in this evaluation. The products can also be also applied with brushes or rollers. This document does not constitute nor should be construed as an EPA endorsement of any particular product, service, or technology. 1 ------- Test Design An important objective of the evaluation was to determine if the wet strippable coatings would adhere adequately to a vertical surface. Figure 2 shows several concrete coupons and a test stand loaded with the coupons. To evaluate the decontamination technologies on vertical surfaces (simulating walls), as well as horizontal surfaces (simulating sidewalks and driveways), a test stand was fabricated that held four rows of six concrete coupons to create surfaces that were approximately 90 centimeters (cm) wide x 60 cm deep (horizontal) or tall (vertical). Concrete coupons were made of standard building concrete that met the specifications for both Type I and II Portland cements. Each coupon was 15 cm square and 4 cm thick. Six of the 24 coupons used to construct each surface were contaminated with Cs-137 (approximately 53 microcuries [pCi]). rm Figure 2. Concrete Coupons (left) and Test Stand With Contaminated Coupons (right) - H is horizontal and V is vertical, A-F indicate the surface positions After the coupons were contaminated with Cs-137, some were allowed to age for 7 days and some for 30 days prior to their placement in the test stand for application and removal of the coatings. Following application, the coatings were allowed to dry overnight, and then removed by first scoring an edge with a paint scraper and then pulling the coating off the surface by hand or scraping lightly. Following the manufacturers' recommendations, this application and removal process was repeated three times. Figure 3 shows the removal processes for each coating. ¦' —- — Z 1 L 1 Figure 3. Removal of Stripcoat TLC Free™ (left) and Removal of Orion™ SC (right) After the final removal of the coatings, the residual radioactivity on the coupons was measured. The decontamination efficacy was determined from the difference in activity before and after application of the decontamination technologies. October 2008 E PA/66 O/S-O 8/021 1 VD VC VE VB VF VA HB / HA HC HD HE HF . ¦ tint This document does not constitute nor should be construed as an EPA endorsement of any particular product, service, or technology. 2 ------- Performance and Results The decontamination efficacy calculated for each of the contaminated coupons is expressed as percent removal (%R). Table 1 gives the Cs-137 activity on the concrete coupons before and after the application of the coatings for the 7-day and 30-day tests in both horizontal and vertical orientations. • For Stripcoat TLC Free™, the overall average %R for the 7-day and 30-day tests was 32.0 ± 9.9. • For Orion™ SC, the overall average %R for the 7-day and 30-day tests was 76.2 ± 7.4. • For each technology, %Rs from the 7-day and 30-day tests were not significantly different from one another. • For each technology, %Rs from the vertical and horizontal surfaces were not significantly different from one another. Table 1. Decontamination Efficacy Results for 7-Day and 30-Day Tests Strippabfe Coating Technology (Company) Days Following Contamination and Orientation3 Pre-Decontarni nation Cs-137 Activity pCib Post-Decontamination Cs-137 Activity pCib Cs-137 %Rb 7 H 56.8 ±1.7 38.3 ±4.5 32.5 ±8.5 7 V 53.5 ± 1.7 38.5 ±5.3 28.0 ±9.8 Stripcoat TLC Free™ (Bartlett Services Inc.) 7 Overall 55.2 ±2.4 38.4 ±4.7 30.3 ±9.0 30 H 53.2 ±3.0 34.3 ± 5.8 35.8 ± 8.7 30 V 55.6 ±1.4 37.8 ± 7.0 31.9± 13.0 30 Overall 54.4 ±2.6 36.0 ±6.4 33.8 ± 10.7 7 H 55.7 ±1.3 11.3 ± 2.3 79.7 ±4.1 7 V 53.6 ± 1.5 12.0 ±2.6 77.5 ± 5.2 Orion™ SC 7 Overall 54.6 ± 1.7 11.7 ± 2.3 78.6 ±4.6 (Isotron Corp.) 30 H 53.6 ±1.8 12.9 ±6,5 76.2 ±11.2 30 V 53.3 ± 1.9 15,3 ±3,8 71.5 ±6.3 30 Overall 53.5 ± 1.8 14,1 ±5,2 73.8 ±9.0 3 Orientation: H indicates horizontal surface, V indicates vertical surface, and Overall, the average of horizontal and vertical surfaces. b Data are presented in terms of average and standard deviation. October 2008 E PA/66 O/S-O 8/021 This document does not constitute nor should be construed as an EPA endorsement of any particular product, service, or technology. 3 ------- Operational factors gathered from these evaluations are identified and summarized in Table 2. Table 2. Strippable Coating Operational Factors Factors Stripcoat TLC Free™ (Bartlett Services Inc.) Orion™ SC (Isotron Corp.) Application and removal Application: 12 m2/hr Removal: 4.9 m2/hr Application: 4.6 m2/hr Removal: 1.6 m2/hr Ease of use on irregular surfaces Elastic coating readily peels off surface Some scraping might be required Labor requirements No specialized training No specialized training Utility requirements If sprayer used, 110 v; otherwise none If sprayer used, 110 v; otherwise none Portability Portable Portable Secondary waste Solid waste production: -0.26 kg/m2 Solid waste density: -0.145 g/cm3 Solid waste production: -0.5 kg/m2 Solid waste density: -0.188 g/cm3 Surface damage Minimal, only loose particles removed Minimal, only loose particles removed Preparation and cleanup Product used "as is"; pump rinsed with mineral spirits between applications to avoid clogging Product requires mixing; pump rinsed with water between applications Cost $16.66/m2 for one application $58.84/m2 for one application Unit definitions: m2=square meters, hr=hour, v=volt, g=gram, kg=kilogram, and cubic centimeters=cm3 The removal rate of Orion™ SC will likely depend on the characteristics of the surface being decontaminated, because some scraping is required for removal. The Stripcoat TLC Free™ can be applied to irregular surfaces and is easily removed across the borders of the coupons CONTACT INFORMATION For more information, visit the EPA Web site at www.epa.gov/nhsrc. Technical Contact: John Drake (drake.john@epa.gov) General Feedback/Questions: Kathv Nickel (nickel.kathv@epa.gov) October 2008 E PA/66 O/S-O 8/021 This document does not constitute nor should be construed as an EPA endorsement of any particular product, service, or technology. 4 ------- |