(21a) Commercial Scale Tritium Recovery From Exit Signs and Other Illumination Devices at LLNL

Diane K. Spencer
J. Mark Mintz
Matthew G. Lucas
and
Dale M. Holck
Weapons and Complex Integration Directorate
Lawrence Livermore National Laboratory
P.O. Box 808 (L-372)
Livermore, CA 94551
Phone (925) 423-8394/Fax (925) 423-1784
spencer2@llnl.gov, mintz1@llnl.gov, lucas3@llnl.gov

Abstract

The disposal of exit signs and similar commercially available tritium-powered illumination devices (TPIDs) in landfills can pose potential public health and environment risks. Studies of active landfills in various states and countries show leachate with tritium considerably above background, with the tritium concentration in many above the Environmental Protection Agency's drinking water MCL of 20,000 pCi/L and between 100,000 pCi/L and 200,000 pCi/L in others. The environmental contamination risk posed by improper disposal of obsolete TPIDs can be greatly reduced by collecting the gaseous tritium remaining in TIPDs. Beginning 2001, LLNL and the U.S. Army have been engaged in a successful tritium recovery and recycle program for a limited number of their specialized devices. This laboratory-scale work has been accomplished by hand with reasonable efficiency. Requests for assistance with similar work, however, include unit volumes in the millions and require much larger capabilities. As a result, the LLNL Tritium Facility has installed a commercial-scale tritium recovery systemâ??the Tritium Grinder System (TGS)â??to complement its laboratory-scale tritium recovery capabilities. The TGS can process up to 72 standard exit signs in a batch, with significantly more for smaller illumination devices (e.g., 2250 rotary phone dials per batch).  The "grinder" portion of the TGS is a commercially available shredder unit from SSI Shredding Systems, Inc., modified to operate under vacuum. A TIPD batch is delivered to the grinder by conveyor belt and is mechanically shredded. The released tritium, along with decay product 3He and Ar added as a sweep gas, is then vacuum-pumped to a collection tank. The collected gas is processed through a regenerable hydrogen getter to remove the tritium product. Solid debris (e.g., exit sign housing residuals) generated through the recovery process is collected in a lined 55-gallon drum using a "bagout" process engineered to minimize outgassing and worker exposure. Upon completion of the bagout process, the content of the drum is ready for final disposal as low-level radioactive waste. Results from initial grinder operations including the collected gas composition and unit processing rate are presented along with a summary of the design features, operating procedures, and safety controls.

Acknowledgments
This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.