A Multilayered Air Monitoring System Used During the Remote Dismantlement of a Hot Cell Process Box
M. V. Taylor, K. E. Taylor, K. M. Kasper
This paper describes the design of a multilayered air monitoring system used for monitoring concentrations of airborne radioactivity during the dismantlement of a hot cell process box contaminated with Sr-90. The air monitoring system includes real-time monitoring of airborne activity inside a containment system, continuous air sampling (during work activities) outside a containment system, grab air samples inside the hot cell process box, and real-time monitoring of air emissions to the environment. Real-time air monitoring includes the use of four alarming constant air monitors (CAM). Sampling heads are normally positioned to monitor the primary and secondary containments, the isolation room of an adjoining hotcell that is used to handle materials removed from the process box, and the air effluent to the environment. Sample filters are screened and counted onsite. Other air samples are taken with various kinds of air samplers during work activities in areas that do not have real-time air sampling and that have the possibility of exceeding 0.5% of the Sr-90 (Class Y) derived air concentration (DAC) value. These air samples are counted onsite to determine airborne concentration levels and containment integrity and performance. There is no continuous air monitoring using a CAM in the process box because of the possibility of contaminating the CAM's radial head. Instead, air samples are collected with RAS samplers with a quick disconnect sampling head attached to the end of a plastic/tygon air tube. The tubes are lowered inside the process box along robot tethers or through a glove box located inside the containment structure. Following high-efficiency particulate air (HEPA) filtration, the hot cell air exhaust line discharges to the outside atmosphere. An alarming CAM at the common exhaust plenum is constantly measuring discharge air quality. This CAM uses a special remote monitoring head that allows the detector to be in the exhaust plenum and the instrument readout and alarms to be located in the operations area.
This abstract was presented at the 37th Annual Midyear Meeting, "Air Monitoring and Internal Dosimetry", Workplace Air Monitoring, Part 2 Session, 2/8/2004 - 2/11/2004, held in Augusta, GA.