"During the Manhattan Project (1943-1947), Y-12 conducted indoor air monitoring for purposes of assessing worker exposures to airborne uranium and determining the amount of uranium being lost to the atmosphere (Smith et al. 1945). Uranium concentrations in indoor air were determined through the collection of periodic grab (short term) air samples. Measurement techniques used in obtaining grab samples were crude by today's standards, however, these did provide quantitative estimates of the relative amounts of uranium that were present in the production areas that may have been lost through general building ventilation and exhaust hoods. Air sampling equipment commonly used at Y-12 during this period was developed by the University of Chicago and consisted of a high-efficiency asbestos-based filter paper through which air was drawn to collect airborne particles. The filter paper was manufactured by the Hollingsworth and Vose Company and was known as the H V No. 9081 or the H V No. 8912. The paper was formed into a cylinder, supported by a special "bird cage," and placed in the sample apparatus, commonly referred to as filter tubes. Flowmeters were used to set the proper sampling flow rate. The rest of the sampling equipment consisted of a holder and plugs for the filter tube, a vapor removing canister, a source of suction (Filter Queen Vacuum Cleaner), and a bleed valve for controlling air flow (Berggren 1947).
The filter paper tubes were then measured for gross alpha radioactivity (counts per minute) in Building 9203. A background (blank) filter tube was also counted and subtracted from the sample count for determining the net amount of Y-12 uranium on the sample. Uranium releases were reported by converting the net counts per minute to net activity7 and then to mass (e.g., grams) by applying the specific alpha activity in a sample. Samples usually had the same specific activity as the uranium being processed in the sampling area. When the uranium isotopic concentration was different or unknown, Y-12 then collected samples of the process uranium and performed a specific alpha activity analysis using measurement techniques such as fluorometry."
- Source: Uranium Releases From The Oak Ridge Reservation - A Review Of The Quality Of Historical Effluent Monitoring Data And A Screening Evaluation Of Potential Off-Site Exposures. Oak Ridge Health Studies, Oak Ridge Dose Reconstruction, Task 6 Report, July 1999, Page 2-5.
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