Raman spectroscopy allows for the identification of a diverse range of solid and liquid target samples but its application in nuclear decommissioning operations is limited by low sensitivity due to an inherently weak optical scattering process. Access constraints and high radiation fields can prevent the spectrometer from functioning at its typical effective range. A joint project initiated by Dallas-based Jacobs and U.K.-based IS Instruments has resolved these issues with the development of a new type of Raman spectroscopy system engineered to accurately and safely detect radioactive contamination.

The new system incorporates hollow core microstructured fiber optics to draw the target gas species into the The Raman probe can take measurements in highly radioactive environments. Source: Jacobsinternal volume of the hollow core structure. Raman spectra of the gas within the fiber is captured via a hardware configuration comprising a laser, dispersive spectrometer and coupling optics. The probe can be used to substantially increase the sensitivity of Raman gas phase measurements while exploiting the selectivity advantage of Raman spectroscopy. Mounting the instrument onto a robotic arm enables measurements to be made within 2 m of a target. Data from the optical cable is transmitted to the Raman analyzer located at a position tens of meters distant.

The monitoring system is being deployed to detect uranium and substances used in reprocessing operations, such as kerosene and tri-butyl phosphate, which can indicate the presence of plutonium or uranium contamination. The device is expected to also be of value in other applications where human access is impossible or problematic.