South Texas Project had long used lead wool blankets to shield their Primary Sample Panel, an area of the site within Chemistry that sees a lot of traffic. These lead wool blankets were affixed to the Primary Sample Panel via independent high strength magnets that attached to the grommets. With the blankets turned on their side, and with the imprecise nature of placing the magnet for hanging, the lead wool blankets sagged. Standard lead wool blankets just didn’t fit the application correctly. The shielding was not aesthetically pleasing nor did it attenuate very well. Consequently, it was necessary to use a supplementary shielding rack at the entry way.
South Texas Project sought to replace this ill-fitting shielding package. NPO developed a simple set of magnetic T-Flex Bismuth tiles that fit the exact dimensions needed. The magnetic tiles were 12″ wide x 18″ tall (305 mm x 457 mm) and weighed 44 lb (20 kg) each. This new and improved shielding fit neatly in a row, providing excellent dose reduction. Readings went from 6 mRem/hr (60 μSv/hr) to 1.5 mRem/hr (15 μSv/hr), or a 75% reduction.
Additionally, STP replaced their shielding rack with a new one. This new rack held T-Flex Bismuth blankets, creating a 3′ wide x 6′ tall (0.91 m x 1.83 m) shielding area. The rack also featured a steel cover to make the rack more aesthetically pleasing and fit in with the office environment.
While they had used this supplementary rack in the past with the old blankets, the new T-Flex Bismuth shielding was so effective, that the supplementary rack was no longer necessary. The rack was left in place in case of emergencies and to further reduce dose. Overall, workers have much more confidence in the effectiveness of the new shielding package.
