DECONTAMINATION & DECOMMISSIONING | VESSEL CLEANING Each third of a section took roughly 6.75 hours to
complete meaning roughly two to three days to complete each baffle-to-baffle area. After each section was completed, visual confirmation was made to verify the cleanliness of the vessel before rigging to the next area. One of the lessons learned was that as the liner fell to the floor and piled up, it greatly increased the radiation hazards to the workers at the floor level. Whereas at first the levels would allow for 15 minutes this effect had now increased exposure levels significantly, cutting the allowable exposure time to as low as 45 seconds at the vessel entrance near the floor. After this issue was identified, the customer assumed responsibility for removing any debris on the floor during off-shift hours for the water blasting crew. Material removal was completed using vacuum systems and the clean up resulted in a gradual increase in the permissible work time around the tanks as the project advanced. After eliminating 90 to 95% of the liner using the 3-D
tooling system, the workers were able to dedicate more than 2 hours at a time to finalize touch-ups and remove the remaining 5% of the liner by hand using water jetting methods from inside the tank. Scaffolding was erected at roughly 22 feet high and was sectioned off, creating four levels inside the space for inspection. The workers conducted the final cleanup, by hand, from the top level of the scaffold, rinsing on their way down. Within the vessel, workers had to adhere to strict PPE
requirements. No radiation particles from the liner were to contact the skin or enter the body. This was achieved by
wearing chemical protective garments, full face Powered Air Purifying Respirator (PAPR) with P100 filtration, full rubber gear (over the top of the chemical protection garments) and rubber gloves with nitrile gloves underneath. Each seam was duct taped to prevent any water or hazardous materials from entering. A buddy check system was established after the worker donned the personal protective equipment to ensure that no spots were missed, or skin could be exposed to the hazardous environment. These methods for correctly donning and doffing equipment happened each time entry was made. The use of decontamination rooms and daily urination screening was completed for each worker entering the vessel to ensure that no exposure to the contaminants took place for the individual. Crews working within the building housing the vessels also had to wear a personal dosimeter (EPD) to monitor their daily levels. All equipment that was to leave the site had to adhere to Canadian Nuclear Standards and was therefore decontaminated and scanned for radiation particles before leaving the site. After clearance was granted, the high-pressure system was thus permitted to leave the site. The project was completed with 100% of the liner
removed within the time frame allowed. The major success of the assignment was there were no health and safety concerns or incidents. With the help from the customer and the supporting members of the team, the project went off without any extreme delays and overcame the complications uranium exposure creates. ■
Decommissioning Active Pipelines
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stevevick.com SVI Nuclear Engineering Advert 178x124
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