Tritium Exit Signs

A large retail company was concerned about potentially leaking tritium-bearing exit signs at its stores nationwide. The company asked NV5 to inspect the signs on-site at its stores, remove and replace leaking signs, and package and ship broken signs to a licensed manufacturer. As part of this effort, we also characterized any residual contamination that resulted from a leakage by taking swipes of the sign mounting area, floors, and walls; decontaminated any contaminated areas to meet regulatory standards; and disposed of radioactive waste generated during decontamination. We evaluated individuals who might have been exposed to the tritium leakage and informed employees about the risks associated with tritium exposure. After each store visit, we generated a report that documented damaged signs at the store, the disposition of each sign, the survey and its results, bioassay activities, and recommended follow-up actions.

Because there was no readily applicable standard for this project, NV5 worked with the client and many regulators to develop a consistent approach and standard that would meet all regulatory requirements. It was determined that U.S. Nuclear Regulatory Commission (NRC) Regulatory Guide 1.86 values for beta- and gamma-emitting radionuclides were an acceptable basis for action levels. Although some states allow higher levels, we recommended (and the client decided to adopt) the more conservative Regulatory Guide 1.86 as the basis for the action levels. In addition, we used International Commission on Radiological Protection (ICRP) Publications 67 and 68 to calculate and model tritium doses.

Throughout the course of this project, we oversaw 35 health physicists who conducted 550 store visits in 45 states and Puerto Rico. Of the several thousand tritium-bearing exit signs we inspected for leakage, 800 were found to have lost integrity in one or more tritium-bearing tubes and were disposed of properly.




Radiation Safety

Key Facts

  • NRC Reg Guide 1.86
  • ICRP Publications 67 & 68
  • 550 Store Visits