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Measurements by Transient Infrared Spectroscopies (TIRS)

An infra-red chemical analysis technique developed at Ames Lab is making the transition from a laboratory technique to an on-line, real-time monitor which is proving useful for a wide variety of applications.

Common in laboratories, infrared analysis indicates the details of a material's molecular makeup from the infrared spectrum, but it requires that samples that are otherwise opaque to infrared be thinned or diluted. Transient infrared spectroscopy (TIRS) overcomes this limitation on-line by heating or cooling the surface of the moving material to create a thin, non-opaque surface layer for analysis. The results are detailed chemical analyses for a wide variety of materials including most non-metallic, non-volatile solids and viscous liquids.

For the past few years, the Ames Lab group has been adapting TIRS to a range of applications including DOE's cleanup needs and the private-sector’s quality control needs.

In 1996, a TIRS unit was installed at Rocky Flats Environmental Technology Site in Golden, CO, for monitoring DOE's polymer encapsulation process for immobilizing low-level waste where it allowed very tight control of the encapsulation process. In 1997 work began on adapting TIRS to monitoring plutonium and other radionuclides in molten glass streams during vitrification of high-level wastes and nuclear material. A site test at Savannah River demonstrated the suitability of the analyses to the glass streams.

Numerous applications of TIRS to industrial needs are also being pursued. Already, it has been demonstrated as a polymer cure monitor on process lines for a number of manufacturers. Currently work is going on to apply TIRS to the forest products industry where it can be used to monitor wood composition (e.g., hemicellulose, glucan, and lignin content) from moving wood chips. Further applications are forthcoming.



  • Provides Needed Monitoring - Ames Lab's Transient Infrared Spectroscopy (TIRS) allows for continuous, real-time monitoring necessary to control quality and optimize process efficiency.
  • Versatile - TIRS works on most non-metallic, non-volatile solids as well as on viscous liquids.
  • High Efficiency and Quality - Real-time and precise analysis allow operators to make immediate adjustments to maintain and improve product quality and process efficiency.
  • Easy to Operate - Computerized operation and record-keeping make the TIRS monitoring system easy to use by technicians with minimal training while still insuring accuracy.
  • Provides Regulatory Documentation - For waste processing, on-line analyses provide a continuous record of the composition of the process stream at any moment.  Thus, TIRS validates the integrity of the waste form so that it can be certified, transported and disposed of properly.  



An Ames Lab technique originally developed for monitoring industrial process streams is now helping DOE improve waste solidification with continuous on-line quality control and documentation.



J. J. McClelland and R. W. Jones, "Apparatus and Method for Transient Thermal Infrared Spectrometry of Flowable Enclosed Materials," U. S. Patent 5 191 215, 1993.

J. F. McClelland and R. W. Jones, "Apparatus and Method for Transient Thermal Infrared Emission Spectrometry," U. S. Patent 5 075 552, 1991.

J. F. McClelland and R. W. Jones, "Apparatus and Method for Transient Thermal Infrared Spectrometry," U. S. Patent 5 070 242, 1991.



Stan Bajic, phone: 515-294-2086, e-mail:
Roger Jones, phone: 515-294-3894, e-mail:
John McClelland, phone: 515-294-7948, e-mail: