SEDL / STP / STP1240-EB / STP14114S

Preliminary Tests of an Infrared Process Monitor for Polyethylene Encapsulation of Radioactive Waste

Wright, SL
Postdoctoral Fellow, Ames Laboratory-USDOE, Iowa State University, Ames, Iowa

Jones, RW
Associate Chemist and Physicist, Ames Laboratory-USDOE, Iowa State University, Ames, Iowa

McClelland, JF
Associate Chemist and Physicist, Ames Laboratory-USDOE, Iowa State University, Ames, Iowa

Kalb, PD
Project engineer, Brookhaven National Laboratory, Upton, NY

Pages: 11    Published: Jan 1996

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Abstract

Polyethylene encapsulation is a process that is being nvestigated for the solidification of radioactive nitrate salts at Brookhaven National Laboratory and Rocky Flats Plant. In the encapsulation process, radioactive-salt waste is mixed with polyethylene pellets, heated, and extruded as a molten stream. Upon cooling, the mixture solidifies to a monolithic waste form with excellent properties for long-term waste storage. This paper describes a novel method to monitor the composition of the salt/polymer stream as it exits the extruder.

The monitor is based on a technique known as transient infrared spectroscopy (TIRS). The TIRS monitor is able to capture the real-time mid-infrared spectrum of the processed waste stream as it exits the extruder. The wealth of chemical information contained in a mid-infrared spectrum makes this technique very appealing for on-line monitoring and process control. Data from the monitor can be used to guide processing, minimize waste volume, and certify the composition of the final waste form.