Determination of the chemical form of tritium in self-luminous signs

Building exit signs containing tritium self-luminous light sources were dismantled, and the light sources were tested to determine the chemical form of tritium in this study. The objective was to quantify the amounts of tritiated water (T2O or TOH) present in the light sources. The light sources consist of sealed glass tubes coated internally with a phosphor (zinc sulfide) and filled with tritium gas (T2). Light source tubes from four exit signs were tested. Two were new signs, one was six years old, and one was thirteen years old. In one of the new signs, the total tritium inventory included two percent tritiated water. Two signs had higher amounts of tritiated water: 4.5% for the other new sign, and 14.5% for the six-year-old sign. In the oldest sign, an accurate inventory of the tritium content was not available, but tritiated water accounted for 12.2% of the total tritium collected for counting. 4 refs., 7 figs., 13 tabs