Fiber Optically Coupled Raman Telescope for the In Situ Standoff Characterization of Residual Wastes

Stored nuclear waste must be retrieved from storage, treated, separated into low-and high-level waste streams, and finally put into a disposal form that effectively encapsulates the waste and isolates it from the environment for a long period of time. Not all of the waste, however, is effectively removed in the tank during bulk retrieval. Some remain in the tank bottom and walls, and also in the ancillary piping. Removal of residual waste is necessary in order to prevent the remaining waste from possible leaching into the environment. Compact, remote detection techniques are therefore needed that can provide chemical identification of the residual waste so that appropriate dissolution steps can be implemented. A novel, compact fiber optic Raman probe with a telescope focusing and Raman collection front optics will be developed and use as a standoff detection and mapping tool for residual wastes in nuclear waste storage tanks. The compact size of the telescope Raman probe will allow remote deployment in the tight portals of nuclear waste storage tanks. A prototype of the all-fiber optically coupled telescope was completed and fully characterized for measuring Raman spectra of likely residual waste compounds at up to 70 feet, a typical internal tank dimension. The prototype was provided to DOE/SRS who demonstrated it successfully with several mixed waste materials at similar standoff distances, and made recommendations for further improvements in Phase II. The Raman telescope will be further developed to incorporate video, autofocus, shielding for high radiation environments and accommodation with typical storage tank openings. A field portable, ruggedized spectrograph will be developed optimized for the telescope and Raman excitation laser, enabling a high sensitivity and wider spectral range for enhanced compound identification. A database of >100 high resolution, full range Raman spectra will be developed of likely residual tank contaminants, supported by chemometric software for spectral matching. Commercial applications and other benefits: The fiber optic Raman telescope probe inspection instrument will be useful to the environmental monitoring community as well as first responders. In Hazmat operations, such a device can be used to characterize hazardous chemicals such as chemical spill at a standoff distance and will provide valuable information for the safe handling or remediation of these chemicals.