Abstract: Urine is the most popular matrix used in performance testing programs (PTP) and inter-comparison programs (ICP) for bioassay. Because it comes from humans, there are concerns regarding its biosafety. For large programs, its collection can take several hours or days to complete. In addition, natural urine has an unpleasant smell, which tends to worsen with increasing storage time. In order to solve some of these problems, the Bioassay Section at the Radiation Protection Bureau in Health Canada has been investigating the use of tea in both PTP and ICP exercises. A method based on diluting tea steeps and scanning them in the UV-VIS range of the light spectrum to select appropriate concentrations as simulated urine for the programs has been published. So far, however, only single 3H and single 14C in tea have been studied. The results were found to be compatible and very successful under the S-106 standard of the Canadian Nuclear Safety Commission. This report is an extension of similar investigations and shows that tea samples spiked with both 3H and 14C (DUAL) are also compatible and produce excellent PTP results.