Acoustic detection of pressure in sealed drums

At many waste sites, transuranic (TRU), low-level, and mixed wastes are stored in 55-gallon drums. Many of these drums contain hazardous, organic wastes as well. Radiolysis or other physical or chemical processes may result in gaseous emissions inside these drums. When this happens the pressure within the drum will increase, sometimes to unacceptable levels. In more drastic cases, these emissions may produce flammable or explosive atmospheres (e.g., hydrogen from radiolysis). Currently regulatory procedures requires that each drum be individually opened and inspected for the presence of hazardous organic waste. This situation will be dangerous for workers. A nonintrusive technique has been developed which will detect an increase in pressure over ambient levels and alert workers of potential danger and greatly increase safety. When a drum lidis tapped, it vibrates at specific frequencies. It turns out that the natural frequencies of vibration of the drum lid increase as the pressure inside the drum increases. Thus the pressure within the drum can be determined by measuring the frequency at which the drum lid vibrates. Experimental results and plans to incorporate this into a simple handheld device will be discussed. [Work supported by DOE.]