tPA 600/R-11/Q13 | May 2011 ] www.epa.gov/ord United States Environmental Protection Agency Industrial Contractors Supplies, Inc. Surface Dust Guard with Diamond Wheel for Radiological Decontamination TECHNOLOGY EVALUATION REPORT Office of Research and Development National Homeland Security Research Center ------- EPA 600/R-11/013 May 2011 Technology Evaluation Report Industrial Contractors Supplies, Inc. Surface Dust Guard with Diamond Wheel for Radiological Decontamination John Drake Task Order Project Officer National Homeland Security Research Center Office of Research and Development U.S. Environmental Protection Agency 26 Martin Luther King Drive Cincinnati, OH 45268 ------- Disclaimer The U.S. Environmental Protection Agency (EPA), through its Office of Research and Development's National Homeland Security Research Center, funded and managed this technology evaluation through a Blanket Purchase Agreement under General Services Administration contract number GS23F0011L-3 with Battelle. This report has been peer and administratively reviewed and has been approved for publication as an EPA document. Mention of trade names or commercial products does not constitute endorsement or recommendation for use of a specific product. Questions concerning this document or its application should be addressed to: John Drake National Homeland Security Research Center Office of Research and Development U.S. Environmental Protection Agency 26 West Martin Luther King Dr. Cincinnati, OH 45268 513-569-7164 drake.john@epa.gov li ------- Foreword The Environmental Protection Agency (EPA) holds responsibilities associated with homeland security events: EPA is the primary federal agency responsible for decontamination following a chemical, biological, and/or radiological (CBR) attack. The National Homeland Security Research Center (NHSRC) was established to conduct research and deliver scientific products that improve the capability of the Agency to carry out these responsibilities. An important goal of NHSRC's research is to develop and deliver information on decontamination methods and technologies to clean up CBR contamination. When directing such a recovery operation, EPA and other stakeholders must identify and implement decontamination technologies that are appropriate for the given situation. The NHSRC has created the Technology Testing and Evaluation Program (TTEP) in an effort to provide reliable information regarding the performance of homeland security related technologies. TTEP provides independent, quality assured performance information that is useful to decision makers in purchasing or applying the tested technologies. TTEP provides potential users with unbiased, third-party information that can supplement vendor-provided information. Stakeholder involvement ensures that user needs and perspectives are incorporated into the test design so that useful performance information is produced for each of the tested technologies. The technology categories of interest include detection and monitoring, water treatment, air purification, decontamination, and computer modeling tools for use by those responsible for protecting buildings, drinking water supplies and infrastructure, and for decontaminating structures and the outdoor environment. Additionally, environmental persistence information is also important for containment and decontamination decisions. NHSRC is pleased to make this publication available to assist the response community to prepare for and recover from disasters involving CBR contamination. This research is intended to move EPA one step closer to achieving its homeland security goals and its overall mission of protecting human health and the environment while providing sustainable solutions to our environmental problems. Jonathan G. Herrmann, Director National Homeland Security Research Center 111 ------- Acknowledgments Contributions of the following individuals and organizations to the development of this document are gratefully acknowledged. United States Environmental Protection Agency (EPA) John Drake Emily Snyder Sang Don Lee Lukas Oudejans David Musick Kathy Hall Eletha Brady-Roberts Jim Mitchell University of Tennessee Howard Hall United States Department of Energy's Idaho National Laboratories Battelle Memorial Institute iv ------- Contents Foreword iii Acknowledgments iv Abbreviations/Acronyms vii Executive Summary viii 1.0 Introduction 1 2.0 Technology Description 3 3.0 Experimental Details 4 3.1 Experiment Preparation 4 3.1.1 Concrete Coupons 4 3.1.2 Coupon Contamination 5 3.1.3 Measurement of Activity on Coupon Surface 5 3.1.4 Surface Construction Using Test Stand 6 3.2 Evaluation Procedures 6 4.0 Quality Assurance/Quality Control 8 4.1 Intrinsic Germanium Detector 8 4.2 Audits 9 4.2.1 Performance Evaluation Audit 9 4.2.2 Technical Systems Audit 9 4.2.3 Data Quality Audit 10 4.3 QA/QC Reporting 10 5.0 Evaluation Results 11 5.1 Decontamination Efficacy 11 5.2 Deployment and Operational Factors 12 6.0 Performance Summary 15 6.1 Decontamination Efficacy 15 6.2 Deployment and Operational Factors 15 7.0 References 16 v ------- Figures Figure 2-1. Angle grinder equipped with SDG and DMD (left). DMD (right) 3 Figure 3-1. Demonstration of contaminant application technique 5 Figure 3-2. Containment tent: outer view (left) and inner view with test stand containing contaminated coupons (right) 6 Figure 3-3. SDG-DMD being applied to concrete coupon 7 Figure 5-1. Concrete coupon demonstrating surface damage 12 Tables Table 3-1. Characteristics of Portland Cement Clinker Used to Make Concrete Coupons 4 Table 4-1. Calibration Results - Difference from Th-228 Calibration Energies 8 Table 4-2. NIST-Traceable Eu-152 Activity Standard Check 9 Table 5-1. Decontamination Efficacy Results 12 Table 5-2. Operational Factors Gathered from the Evaluation 14 vi ------- Abbreviations/Acronyms ANSI American National Standards Institute ASTM American Society for Testing and Materials BQ Becquerel Cs cesium cfm cubic feet per minute cm centimeters cm2 square centimeters DARPA Defense Advanced Research Projects Agency DF decontamination factor DHS U.S. Department of Homeland Security DMD diamond cutting wheel DOD Department of Defense EPA U.S. Environmental Protection Agency Eu europium Ft feet HEPA High Efficiency Particulate Air IEEE Institute of Electrical and Electronics Engineers INL Idaho National Laboratory keV kilo electron volts kg kilogram mg milligram mL milliliter L liter m meter m2 square meters jj.Ci microCurie NHSRC National Homeland Security Research Center NIST National Institute of Standards and Technology ORD Office of Research and Development %R percent removal PE performance evaluation QA quality assurance QC quality control QMP quality management plan RDD radiological dispersion device RML Radiological Measurement Laboratory RSD relative standard deviation SDG Industrial Contractors Supplies, Inc. Surface Dust Guard SDG-DMD Industrial Contractors Supplies, Inc. Surface Dust Guard with a diamond cutting wheel TSA technical systems audit TTEP Technology Testing and Evaluation Program Th thorium V volt vii ------- Executive Summary The U.S. Environmental Protection Agency's (EPA) National Homeland Security Research Center (NHSRC) is helping to protect human health and the environment from adverse impacts resulting from acts of terror by carrying out performance tests on homeland security technologies. Through its Technology Testing and Evaluation Program (TTEP), NHSRC evaluated the performance of the Industrial Contractors Supplies, Inc. Surface Dust Guard (SDG) with a diamond cutting wheel (DMD) and its ability to remove radioactive cesium (Cs)-137 from the surface of unpainted concrete. Experimental Procedures. The Industrial Contractors Supplies, Inc. SDG is a vacuum shroud that can be attached to almost any commercially available handheld grinder or polisher (e.g. Bosch, DeWalt, and Hitachi, etc). During this evaluation the SDG was used with a Makita 9564CV angle grinder equipped with a DMD. (Hereafter this combination will be referred to as the SDG-DMD). This technology is designed to decontaminate by removing the surface layer and collecting the resulting secondary waste using a vacuum connected to the SDG. Eight 15 centimeter (cm) x 15 cm unpainted concrete coupons were contaminated with approximately 1 microCurie (|iCi) of Cs-137 per coupon and allowed to age for seven days. The amount of contamination deposited on each coupon was measured using gamma spectroscopy. The eight contaminated coupons were placed in a test stand (along with one uncontaminated blank coupon) that was designed to hold nine concrete coupons in a vertical orientation to simulate the wall of a building. Each coupon was sanded with the SDG-DMD and the decontamination efficacy was determined by calculating both a decontamination factor (DF) and percent removal (%R). Important deployment and operational factors were also documented and reported. Results. The decontamination efficacy attained by the SDG-DMD was evaluated for each concrete coupon used during the evaluation. When the decontamination efficacy metrics (%R and DF) of the eight contaminated coupons were averaged together, the average %R for the SDG-DMD was 89 ± 8% and the average DF was 13.7 ± 8.5. Hypothesis testing was performed to determine if there were significant differences between the %R values determined for the coupons in each row (top, middle, and bottom) of the test stand. No differences were found. The SDG- DMD could decontaminate a vertical surface at a rate of approximately 2.7 square meters (m2) per hour. The SDG- DMD caused a significant amount of surface destruction. The texture of the coupon surface is not likely to be important to the efficacy of the SDG-DMD and similar DMD wheel radiological decontamination technologies. The wheel is aggressive enough that it cuts through irregularities in concrete surfaces that may limit the effectiveness of less aggressive techniques. A very limited evaluation of cross-contamination was performed. During an actual decontamination of a vertical surface, the higher elevation surfaces would likely be decontaminated first, possibly exposing the lower surface to secondary contamination. To ------- simulate an actual scenario, one uncontaminated coupon was placed in the bottom row of the test stand and decontaminated using the SDG-DMD in the same way as the other coupons. Following decontamination using the SDG-DMD, the uncontaminated coupon did not contain measurable activity, suggesting that cross contamination was minimal. Overall, the SDG was not entirely effective at containing the secondary waste. There was a significant amount of dust visible during the evaluation. In addition, the radiological control technicians found a small but measurable level of airborne radiological activity from particulate during the evaluation. The dust collected by the vacuum was not analyzed for gamma radiation. IX ------- 1.0 Introduction The U.S. Environmental Protection Agency's (EPA) National Homeland Security Research Center (NHSRC) is helping to protect human health and the environment from adverse effects resulting from acts of terror. NHSRC is emphasizing decontamination and consequence management, water infrastructure protection, and threat and consequence assessment. In doing so, NHRSC is working to develop tools and information that will improve the ability of operational personnel to detect the intentional introduction of chemical, biological, or radiological contaminants on or into buildings or water systems, to contain or mitigate these contaminants, to decontaminate affected buildings and/or water systems, and to dispose of contaminated materials resulting from clean-ups. NHSRC, through its Technology Testing and Evaluation Program (TTEP), works in partnership with recognized testing organizations; with stakeholder groups consisting of buyers, vendor organizations, and permitters; and with the participation of individual technology developers in carrying out performance tests on homeland security technologies. The program evaluates the performance of homeland security technologies by developing evaluation plans that are responsive to the needs of stakeholders, conducting tests, collecting and analyzing data, and preparing peer-reviewed reports. All evaluations are conducted in accordance with rigorous quality assurance (QA) protocols to ensure that data of known and high quality are generated and that the results are defensible. TTEP provides high-quality information that is useful to decision makers in purchasing or applying the evaluated technologies, and in planning clean-up operations. TTEP provides potential users with unbiased, third-party information that can supplement vendor-provided information. Stakeholder involvement ensures that user needs and perspectives are incorporated into the evaluation design so that useful performance information is produced for each of the evaluated technologies. Under TTEP, NHSRC evaluated the performance of the Industrial Contractors Supplies, Inc. (Huntingdon, PA) Surface Dust Guard (SDG) with a diamond cutting wheel (DMD) (hereafter referred to as the SDG-DMD) in removing radioactive isotope Cs-137 from concrete. A peer-reviewed test/QA plan was developed according to the requirements of the quality management plan (QMP) for TTEP. The evaluation generated the following performance information for the SDG-DMD: # Decontamination efficacy, defined as the extent of radionuclide removal following the use of the SDG-DMD, and the possibility of cross-contamination. # Deployment and operational factors, including the approximate rate of surface area decontamination, applicability to irregular surfaces, skilled labor requirement, utility 1 ------- requirements, portability, secondary waste management, and technology cost. This evaluation took place from August 11, 2009 until October 13, 2009. All of the experimental work took place in a radiological contamination area at the U.S. Department of Energy's Idaho National Laboratory (INL). This report describes the quantitative results and qualitative observations gathered during the evaluation. The contractor, Battelle, and EPA were responsible for QA oversight. The Battelle QA Manager conducted both a technical systems audit (TSA) and a data quality audit of the evaluation data. 2 ------- 2.0 Technology Description The following description of the Industrial Contractors Supplies, Inc. SDG is based on information provided by the vendor and was not verified during this evaluation. The Industrial Contractors Supplies, Inc. SDG is a vacuum shroud that can be attached to almost any commercially available handheld grinder or polisher with a 5 inch wheel (e.g. Bosch, DeWalt, and Hitachi, etc). During this evaluation the SDG was used with a Makita 9564CV angle grinder equipped with a DMD (CGD30P45H, Industrial Contractors Supplies, Inc.). (Hence, the SDG-DMD.)The DMD was 10 cm in diameter and had 18 segments of 40/60 medium grit diamond crystal segments. This technology decontaminates bound Cs-137 from surfaces by removing the surface layer and collecting the resulting secondary waste using a high efficiency particulate air (HEPA) vacuum connected to the SDG. The vacuum was powered by 110 volt (V) electricity generating a flow of 136 cubic feet per minute (cfm). The angle grinder component was also powered by 110V electricity; according to vendor specifications, it operates at speeds up to 10,500 revolutions per minute. Figure 2-1 shows the components of the SDG-DMD, Figure 2-1. Angle grinder equipped with SDG and DMD (left). DMD (right). 3 ------- 3.0 Experimental Details 3.1 Experiment Preparation 3.1.1 Concrete Coupons The concrete coupons were prepared from a single batch of concrete made from Type II Portland cement. The ready-mix company (Burns Brothers Redi-Mix, Idaho Falls, ID) that supplied the concrete for this evaluation provided the data which describe the cement clinker used in the concrete mix. For Type II Portland cement, the American Society for Testing and Materials (ASTM) Standard C 150-71 specifies that tricalcium aluminate should account for less than 8% of the overall cement clinker (by weight). The cement clinker used for the concrete coupons was 4.5% tricalcium aluminate (Table 3-1). For Type I Portland cement the tricalcium aluminate should be less than 15%. Because Type I and II Portland cements differ only in tricalcium aluminate content, the cement used during this evaluation meets the specifications for both Type I and II Portland cements. Table 3-1. Characteristics of Portland Cement Clinker Used to Make Concrete Coupons Cement Constituent Percent of Mixture Tricalcium Silicate 57.6 Dicalcium Silicate 21.1 Tricalcium Aluminate 4.5 Tetracalcium Aluminoferrite 8.7 Minor Constituents 8.1 The wet concrete was poured into 0.9 meter (m) square plywood forms with the exposed surface "floated" to allow the smaller aggregate and cement paste to float to the top, and the concrete was then cured for 21 days. Following curing, the squares were cut to the desired size with a laser-guided rock saw. For this evaluation, the "floated" surface of the concrete coupons was used. The coupons were approximately 4 centimeters (cm) thick, 15 cm x 15 cm square, and had a surface finish that was consistent across all the coupons. The concrete was representative of exterior concrete commonly found in urban environments in the United States as shown by INL under a previous project sponsored by the U.S. Department of Defense (DOD), Defense Advanced Research Projects Agency (DARPA) and U.S. Department of Homeland Security (DHS).2 4 ------- 3.1.2 Coupon Contamination Eight coupons were contaminated by spiking individually with 2.5 milliliters (mL) of aqueous solution that contained 0.26 milligrams (mg)/liter (L) Cs-137 as a solution of cesium chloride, corresponding to an activity level of approximately 1 microCurie (|iCi) over the 225 cm2 surface. Application of the Cs-137 in an aqueous solution was justified because even if Cs-137 were dispersed in a particle form following a radiological dispersion device (RDD) or "dirty bomb" event, morning dew or rainfall would likely occur before the surfaces could be decontaminated. In addition, from an experimental standpoint, it is much easier to apply liquids, rather than dry particles, homogeneously across the surface of the concrete coupons. The liquid spike was delivered to each coupon using an aerosolization technique developed by INL (under a DARPA/DHS project2) and described in detail in the test/QA plan. The coupons were then allowed to age for seven days. The aerosol delivery device was constructed of two syringes. The plunger and needle were removed from the first syringe and discarded. Then, a compressed air line was attached to the rear of the syringe. The second syringe contained the contaminant solution and was equipped with a 27 gauge needle, which penetrated through the plastic housing near the tip of the first syringe. Compressed air flowing at a rate of approximately 1 - 2 L per minute created a turbulent flow through the first syringe. When the contaminant solution in the second syringe was introduced, the solution became nebulized by the turbulent air flow. A fine aerosol was ejected from the tip of the first syringe creating a controlled and uniform spray of fine liquid droplets onto the coupon surface. The contaminant spray was applied all the way to the edges of the coupon which were taped (after having previously been sealed with polyester resin) to ensure that the contaminant was applied only to the surfaces of the coupons. The photographs in Figure 3-1 show this procedure being performed using a nonradioactive, nonhazardous aqueous dye to demonstrate that the 2.5 mL of contaminant solution is effectively distributed across the surface of the coupon. Figure 3-1. Demonstration of contaminant application technique. 3.1.3 Measurement of Activity on Coupon Surface Gamma radiation from the surface of each concrete coupon was measured to quantify contamination levels both before and after evaluation of the ETR180. These 5 ------- measurements were made using an intrinsic, high purity germanium detector (Canberra LEGe Model GL 2825R/S, Meriden, CT). After being placed into the detector, each coupon was measured until the average activity level of Cs-137 from the surface stabilized to a relative standard deviation of less than 2%. Gamma-ray spectra acquired from Cs-137 contaminated coupons were analyzed using INL Radiological Measurement Laboratory (RML) data acquisition and spectral analysis programs (PCGAP, Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID; INEEL/EXT-2000- 00908; http://www.inl.gov/technicalpublications/Documents/3318133.pdt*). Radionuclide activities on coupons were calculated based on efficiency, emission probability, and half- life values. Decay corrections were made based on the date and the duration of the counting period. Full RML gamma counting QA/quality control (QC), as described in the test/QA plan, was employed, and certified results were provided. 3.1.4 Surface Construction Using Test Stand To evaluate the decontamination technologies on vertical surfaces (simulating walls), a stainless steel test stand was fabricated that held three rows of three concrete coupons. The test stand, approximately 9 feet (ft) x 9 ft, was erected within a containment tent. The concrete coupons were placed into holders so their surfaces extended just beyond the surface of the stainless steel face of the test stand. Eight of the nine coupons placed in the test stand were contaminated with Cs-137, which has a half-life of 30 years. One uncontaminated coupon was placed in the bottom row of the test stand and decontaminated using the SDG-DMD in the same way as the other coupons. This coupon was placed there to observe possible secondary contamination caused by the decontamination higher on the wall. Figure 3-2 shows the containment tent and the test stand loaded with concrete coupons. Figure 3-2. Containment tent: outer (left) and inner view with test stand containing contaminated coupons (right). 3.2 Evaluation Procedures The containment tent consisted of two rooms. One room contained the test stand to hold the contaminated coupons; the other room (the shorter part of the tent as shown in Figure 3-2) held the vacuum. An opening in the tent wall between the two rooms was just large enough to allow the vacuum hose connected to the SDG-DMD to pass through. The tent 6 ------- opening was taped closed around the hose prior to the start of the evaluation. Figure 3-3 shows the vacuum hose connecting to the SDG as the operator applies the SDG-DMD to a concrete coupon. The nine concrete coupons in the test stand were sanded using the SDG-DMD starting with the top row and working from left to right, then proceeding to the middle and bottom rows. The coupons were sanded in this manner to simulate an approach that would likely be taken in an actual decontamination event, where higher wall surfaces would be decontaminated first because of the possibility of secondary contamination lower on the wall. The SDG-DMD was connected to the vacuum and operated at full power for 20-30 seconds on each coupon, enough time to ensure that the entire surface of each had been covered. This procedure would correspond to a rate of coverage ranging from 0.2 m2 to 0.3 m* per minute. The temperature and relative humidity were recorded before and after the approximately one hour test. These conditions did not vary significantly in the room where the evaluation was performed. Over the duration of testing, the temperature was 17.7 °C and the relative humidity was 26%. Figure 3-3. SDG-DMD being applied to concrete coupon. 7 ------- 4.0 Quality Assurance/Quality Control QA/ QC procedures were performed in accordance with the program QMP and the test/QA plan for this evaluation. 4.1 Intrinsic Germanium Detector The germanium detector was calibrated once each week. The calibration was performed in accordance with standardized procedures from the American National Standards Institute (ANSI) and the Institute of Electrical and Electronics Engineers (IEEE).3 In brief, detector energy was calibrated using thorium (Th)-228 daughter gamma rays at 238.6, 583.2, 860.6, 1620.7, and 2614.5 kilo electron volts (keV). This calibration was performed three times during the overall project and documented by the RML. Table 4-1 gives the difference between the known energy levels and those measured following calibration. The energies were compared to the previous 30 calibrations to confirm that the results were within three standard deviations of the previous calibration results. The calibrations are shown for the detector used during this evaluation. All the calibrations fell within this requirement. Table 4-1. Calibration Results - Difference from Th-228 Calibration Energies Calibration Energy Levels (keV) Date Energy 1 238.632 Energy 2 583.191 Energy 3 860.564 Energy 4 1620.735 Energy 5 2614.533 8-25-2009 -0.005 0.014 -0.031 -0.199 0.031 9-21-2009 -0.003 0.009 -0.040 -0.125 0.015 10-13-2009 -0.003 0.008 -0.011 -0.180 0.020 Gamma ray counting was continued on each coupon until the activity level of Cs-137 on the surface had a relative standard deviation (RSD) of less than 2%. This RSD occurred within an initial 1 hour of counting for all the coupons measured during this evaluation. The final activity assigned to each coupon was a compilation of information obtained from all components of the electronic assemblage that comprise the "gamma counter," including the raw data and the spectral analysis described in Section 3.1.3. Final spectra and all data that comprise the spectra were sent to a data analyst who independently confirmed the "activity" number arrived at by the spectroscopist. When both the spectroscopist and an expert data analyst independently arrived at the same value the data were considered certified. This process defines the full gamma counting QA process for certified results. 8 ------- The background activity of the concrete coupons was determined by analyzing nine arbitrarily selected coupons from the stock of concrete coupons used for this evaluation. The ambient activity level of these coupons was measured for at least two hours. No activity was detected above the minimum detectable level of 2xl0"4 |iCi on these coupons. Because the background activity was not detectable (and the detectable level was 600 times lower than the post-decontamination activity levels), no background subtraction was required. Throughout the evaluation, a second measurement was taken on 10 coupons in order to provide duplicate measurements to evaluate the repeatability of the instrument. Half of the duplicate measurements were performed after contamination prior to application of the decontamination technology and half were performed after decontamination. Five of the duplicate pairs showed no difference in activity levels between the two measurements; the other five duplicate pairs had a difference of 2% between the two measurements, within the acceptable difference of 5%. 4.2 Audits 4.2.1 Performance Evaluation Audit RML performed regular checks of the accuracy of the Th-228 daughter calibration standards (during the time when the detector was in use) by measuring the activity of a National Institute of Standards and Technology (NIST)-traceable europium (Eu)-152 standard (in units of Becquerel, BQ) and comparing it to the accepted NIST value. Results within 7% of the NIST value are considered to be within acceptable limits. The Eu-152 activity comparison is a routine QC activity performed by INL, but for the purposes of this evaluation serves as the performance evaluation (PE) audit, an audit that confirms the accuracy of the calibration standards used for the instrumentation critical to the results of an evaluation. Table 4-2 gives the results of each of the audits applicable to the duration of the evaluation. All results are below the acceptable difference of 7%. Table 4-2. NIST-Traceable Eu-152 Activity Standard Check Relative NIST Activity INL RML Percent Date (BQ) Result (BQ) Difference 8-18-2009 124,600 122,400 2% 9-10-2009 124,600 122,600 2% 10-12-2009 124,600 122,300 2% 4.2.2 Technical Systems Audit A TSA was conducted during testing at INL to ensure that the evaluation was performed in accordance with the test/QA plan and the TTEP QMP. As part of the audit, the actual 9 ------- evaluation procedures were compared with those specified in the test/QA plan, and the data acquisition and handling procedures were reviewed. No significant adverse findings were noted in this audit. The records concerning the TSA are stored indefinitely with the Battelle QA Manager. 4.2.3 Data Quality Audit The Battelle QA Manager verified all of the raw data acquired during the evaluation and transcribed into spreadsheets for use in the final report. The data were traced from the initial raw data collection, through reduction and statistical analysis, to final reporting, to ensure the integrity of the reported results. 4.3 QA/QC Reporting Each assessment and audit was documented in accordance with the test/QA plan and the QMP. The Battelle QA Manager prepared the draft assessment report and sent it to the Test Coordinator and Battelle TTEP Program Manager for review and approval. The Battelle QA Manager then sent the final assessment report to the EPA QA Manager and Battelle staff. 10 ------- 5.0 Evaluation Results 5.1 Decontamination Efficacy The decontamination efficacy of the SDG-DMD was measured for each contaminated coupon in terms of percent removal (%R) and decontamination factor (DF). Both of these measurements provide a means of representing the extent of decontamination accomplished by a technology. The %R gives the extent as a percent relative to the activity and the DF is the ratio of the initial activity to the final activity or the factor by which the activity was decreased. These terms are defined by the following equations: %R = (1-Af/Ao) x 100% and DF = A0/Af where A0 is the radiological activity from the surface of the coupon before application of the SDG-DMD and Af is radiological activity from the surface of the coupon after treatment. While the DFs are reported, the narrative describing the results focuses on the %R. Table 5-1 gives the %R and DF for the SDG-DMD. All coupons were oriented vertically. The target activity for each of the contaminated coupons (pre-decontamination) was within the acceptable range of 1 |iCi ± 0.5 |iCi. The overall average (plus or minus one standard deviation) of the contaminated coupons was 1.13 |iCi ± 0.07 |iCi, a variability of 6%. The post-decontamination coupon activities were less than the pre-decontamination activities, showing an overall reduction in activity. The %R averaged 89% ± 8% and the DF averaged 13.7 ± 8.5. Overall, the %R ranged from 72% to 97% and the DF ranged from 3.5 to 30.5. Paired t-tests were performed at a 95% confidence interval to determine whether location (top, middle, or bottom) on the test stand affected the decontamination efficacy. While the average %R for the top row (95% ± 2%) of coupons was slightly higher than the middle (84%+ 11%) and bottom (88%+ 6%) rows, no significant difference between any of the rows was found. The bottom middle coupon was not contaminated to test the possibility of cross-contamination. Activity of the uncontaminated coupon was measured after all nine coupons had been decontaminated using the SDG-DMD. No activity was detected on the uncontaminated coupon, suggesting that cross-contamination due to the application of the SDG-DMD was minimal. 11 ------- Table 5-1. Decontamination Efficacy Results Coupon Location in Pre-Decon Activity Post-Decon Activity Test Stand (iCi / Coupon jiCi / Coupon %R DF Top left 1.19 0.07 94 17.4 Top middle 1.14 0.07 94 15.6 Top right 1.16 0.04 97 30.5 Center left 1.12 0.07 94 16.6 Center middle 1.18 0.15 87 7.7 Center right 1.10 0.31 72 3.5 Bottom left 1.18 0.10 92 11.9 Bottom right 0.99 0.16 84 6.2 Average 1.13 0.12 89 13.7 Std. Dev 0.07 0.09 8 8.5 5.2 Deployment and Operational Factors A number of operati onal factors were documented by the SDG-DMD operator. One of the factors was damage to the surface of the concrete coupons. Figure 5-1 shows a non- contaminated coupon that has had the bottom third sanded with the SDG-DMD and the top two-thirds left unsanded. The slight pink color is due to a dye that was applied to the surface of this noncontaminated coupon for illustrative purposes. The bottom of the coupon has had the surface characteristics (pink color, smooth concrete finish, etc.) stripped away. One large piece of aggregate on the left side of the coupon fell out during sanding; several dark colored pieces of aggregate are visible in the bottom third but not in the top two-thirds of the coupon. The SDG-DMD can damage any concrete surface on which it is used. Figure 5-1. Concrete coupon demonstrating surface damage. 12 ------- Other important factors to consider are the personal protection of the technology operators and the secondary waste management of a decontamination technology. During this evaluation, the radiological control technicians required the operators to wear full anti-contamination personal protective equipment that included a full face respirator with supplied air. This level of personal protection was required because of the likelihood of airborne radiological contamination due to the act of sanding. However, each situation will need to be considered independently by local RCTs to determine the proper level of personal protection. Overall, the SDG was not entirely effective at containing the secondary waste. During the evaluation a significant amount of dust was visible and the radiological control technicians found a small, but measurable, level of airborne radiological activity. Because the vacuum was in a separate room of the tent, the vacuum is unlikely to have contributed to the airborne contamination. In an actual decontamination situation, the possibility of the release of airborne radiological activity would be a safety concern. Table 5-2 summarizes qualitative and quantitative practical information gained by the operator during the evaluation of the SDG-DMD. All of the operational information was gathered during use of SDG-DMD on the concrete coupons inserted into the test stand. Some of the information given in Table 5-2 could differ if the SDG-DMD were applied to a larger surface or a surface that was smoother or more rough and jagged than the concrete coupons used during this evaluation. 13 ------- Table 5-2. Operational Factors Gathered from the Evaluation Parameter Description/Information Decontamination rate Technology Preparation: 5 minutes to attach diamond wheel and SDG to angle grinder. Application: 20-30 seconds per concrete coupon used during this evaluation corresponds to an application rate of approximately 2.7 m2/hour; less or more time per coupon may result in different levels of radiological decontamination. Applicability to irregular surfaces Irregular surfaces would likely not be a problem for the SDG-DMD as the diamond wheel is an aggressive decontamination technique, removing the surface of the concrete, making the SDG-DMD not dependent on the surface characteristics of the concrete. Skilled labor requirement The SDG-DMD is an extremely basic technology requiring minimal training. Adequate training would likely include a few minutes of orientation so the operator is familiar with the power switches on the vacuum and the SDG- DMD. The SDG-DMD weighs approximately 2 kilogram (kg). The operator during this evaluation experienced a significant level of exertion as he completed the evaluation. The weight of the SDG-DMD, in combination with the additional weight and awkwardness of the attached vacuum line, increased the level of effort required to use the SDG-DMD. Depending on what row of the test stand was being used, the operator was required to bend over, stand on the floor or stand up on a ladder. Each of these situations required a significant amount of exertion. These factors will exclude some people from being able to operate the SDG-DMD. However, most people who are used to performing physical labor should not have any problem operating the SDG- DMD. Utilities requirement 110 V power for both the SDG-DMD and a 136 cfm vacuum. Portability The limiting factors of portability for the SDG-DMD will include the availability of power and the ability to connect to the vacuum by staying close enough to the vacuum or by having a vacuum hose of adequate length. Decontamination media The same DMD was used for all nine coupons that were decontaminated. Secondary waste management Some dust was expelled from the DMD and vacuum shroud during testing. The radiological control technicians who observed the testing collected airborne particulate and detected small, but measurable amounts of activity in the air during evaluation of the SDG-DMD. The activity of the dust collected by the vacuum or vacuum filter was not measured quantitatively. However, given the effectiveness of the SDG-DMD, presumably the waste had significant activity levels. Surface damage See description and picture in text. Cost $1,000 for the entire system, including the angle grinder, SDG, and vacuum. The SDG alone costs $235. 14 ------- 6.0 Performance Summary This section presents the findings from the evaluation of the SDG-DMD for each performance parameter evaluated. 6.1 Decontamination Efficacy The decontamination efficacy (in terms of %R) attained by the SDG-DMD was evaluated for each concrete coupon used during the evaluation. When the decontamination efficacy metrics (%R and DF) of the eight contaminated coupons were averaged together, the average %R for the SDG-DMD was 89 ± 8% and the average DF was 13.7 + 8.5. Hypothesis testing was performed to determine if there were significant differences between the %R values determined for the coupons in each row (top, middle, and bottom) of the test stand. No differences were found. 6.2 Deployment and Operational Factors The SDG- DMD could decontaminate a vertical surface at a rate of approximately 2.7 m2 per hour. The SDG- DMD caused a significant amount of surface destruction. The texture of the coupon surface is not likely to be important to the efficacy of the SDG-DMD and similar DMD wheel radiological decontamination technologies. The wheel is aggressive enough that it cuts through irregularities in concrete surfaces that may limit the effectiveness of less aggressive techniques. A very limited evaluation of cross-contamination was performed. During an actual decontamination of a vertical surface, the higher elevation surfaces would likely be decontaminated first, possibly exposing the lower surface to secondary contamination. To simulate an actual scenario, one uncontaminated coupon was placed in the bottom row of the test stand and decontaminated using the SDG-DMD in the same way as the other coupons. Following decontamination using the SDG-DMD, the uncontaminated coupon did not contain measurable activity, suggesting that cross contamination was minimal. Overall, the SDG was not entirely effective at containing the secondary waste. There was a significant amount of dust visible during the evaluation. In addition, the radiological control technicians found a small but measurable level of airborne radiological activity 15 ------- from particulate during the evaluation. The dust collected by the vacuum was not analyzed for gamma radiation. 7.0 References 1. ASTM Standard C 150-07, 2007, "Standard Specification for Portland Cement," ASTM International, West Conshohocken, PA, www.astm.org. 2. Radionuclide Detection and Decontamination Program. Broad Agency Announcement 03-013, U.S. Department of Defense (DOD) Defense Advanced Research Projects Agency (DARPA) and the U.S. Department of Homeland Security, classified program. 3. Calibration and Use of Germanium Spectrometers for the Measurement of Gamma Emission Rates of Radionuclides, American National Standards Institute. ANSI N42.14-1999. IEEE New York, N.Y. (Rev. 2004). 16 ------- &EPA United States Environmental Protection Agency PRESORTED STANDARD POSTAGE & FEES PAID EPA PERMIT NO. G-35 Office of Research and Development (8101R) Washington, DC 20460 Official Business Penalty for Private Use $300 ------- |