Technology:
Centrifugal Shot Blast:
- Shot blast unit manufactured by George Fisher (GOFF®). Unit operated with two 1/4 horsepower, variable speed drives, and has a 13-inch cutting width. The vendor advertised production rate is 200-250 ft2/hr.
- HEPA-filter dust collection system manufactured by George Fisher (GOFF®). Six primary roughing filter cartridges, one secondary HEPA filter unit; vendor rated vacuum flow of 850 cubic ft/min
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Cleanup Authority:
Project performed as part of DOE's Large-Scale Demonstration Project, Office of Science and Technology, Deactivation and Decommissioning Focus Area
Regulatory Point of Contact:
Information not provided | Additional Contacts:
Susan C. Madaris
Test Engineer
Florida International University
(305) 348-3727
Richard Baker
DOE
(630) 252-2647 |
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Contaminants:
Radioactive-contaminated paint |
Waste Source:
Contaminated paint coating on concrete floor |
Type/Quantity of Media Treated:
Radioactively contaminated concrete floor - 800 ft2 of concrete flooring covered with contaminated paint |
Purpose/Significance of Application:
Demonstrate a modified centrifugal shot blast unit and compare results with those for mechanical scabbing |
Regulatory Requirements/Cleanup Goals:
The objective of the demonstration was to evaluate the performance of the modified centrifugal shot blast system to remove contaminated paint coating from 800 ft2 of concrete flooring and to compare the results of this technology with those from the baseline technology of mechanical scabbing. |
Results:
- Use of the dust collection system significantly reduced the amount of airborne dust generated during the blasting process and has the potential to lead to the use of less respiratory protection and PPE requirements; the unit is self-propelled and has the potential to reduce operator fatigue; the unit can be adjusted to remove the coating layer only, specific layers of coating, or coating and up to ½ inch of concrete; the end-point condition of the surface in the demonstration was smooth, bare concrete.
- Reduced total fixed beta/gamma contamination levels from pre-demonstration levels as high as 5,300 dpm/100 cm2 to below background levels (1,500 dpm/100 cm2).
- Problems were encountered with the dust collection system assembly and disassembly and with steel shot escaping the unit. According to DOE, additional improvements are needed to make the unit safer and more efficient for use at a DOE facility.
- The main advantage of the modified centrifugal shot blast system over the baseline technology is the ability to simultaneously collect dust and debris using a dust collection system attached to the shot blast unit. |
Cost Factors:
The report presents a detailed cost analysis of this technology compared to the baseline technology.
Cost analysis results show the total cost for centrifugal shot blast was higher than mechanical scabbing (about $23,000 versus about $13,000) and had higher costs for mobilization/demobilization and decontamination for the 800 ft2 demonstration. However, because the incremental cost for centrifugal shot blast is lower, this technology was projected to be less expensive than the baseline for areas greater than 1,900 ft2. |
Description:
Concrete Cleaning, Inc. demonstrated a modified centrifugal shot blast system for removing radioactive contaminated paint from concrete flooring. This demonstration was part of the Chicago Pile-5 (CP-5) Large-Scale Demonstration Project sponsored by DOE, Office of Science and Technology, Deactivation and Decommissioning Focus Area, to demonstrate the benefits of using innovative and improved decontamination and decommissioning technologies. CP-5 was a heavy-water moderated and cooled, highly enriched, uranium-fueled thermal reactor designed to supply neutrons for research and was operated for 25 years before being shut down in 1979.
For this demonstration, Concrete Cleaning modified a standard centrifugal shot blast machine (manufactured by George Fisher) to increase efficiency and speed of substrate removal. Concrete Cleaning considers the modifications to be proprietary and has applied for a patent. The shot blast machine was equipped with a HEPA filter dust collection system that had been modified to replace the refuse pan provided by the manufacturer. The system was modified with a funnel-drum lid system that directed the waste directly into a standard waste drum. This modification reduced the potential for airborne releases by eliminating the need to transfer waste from the pan into the drum for disposal. As the unit was moved across the floor, the shot and substrate debris were vacuumed through the shot blast unit, and passed through an abrasive recycling system. The heavier shot was returned to the unit while the spent shot (too small in size to reuse) was sent to the dust collection system. The demonstration showed that the main advantage of the Concrete Cleaning centrifugal shot blast technology compared to mechanical scabbing was the simultaneous collection of dust and debris. The report includes a detailed comparison of the two technologies. In addition, the results of radiological surveys performed before and after the demonstration showed that blasting had reduced total fixed beta/gamma contamination levels from pre-demonstration levels as high as 5,300 dpm/100 cm2 to below background levels (1,500 dpm/100 cm2).
Several problems were encountered during the demonstration. Steel shot escaping from the unit presented a potential projectile hazard, the magnetic roller was not effective in collecting steel shot left on the floor, and there were problems with the dust collection system assembly and disassembly. According to DOE, additional improvements are needed to make the unit safer and more efficient for use at a DOE facility. The report includes results of a detailed cost analysis comparing the centrifugal shot blast technology with mechanical scabbing. While the baseline technology was less expensive for the scope and conditions of the demonstration, for areas larger than about 1,900 ft2, the centrifugal shot blast technology was projected to be less expensive because of lower incremental costs. |
