A tritium sensor and method are provided. The sensor involves the use of an electrode having a semiconductor coating that has properties selected to allow the passage of beta particles at the particular energy level for tritium through the semiconductor layer to a conductive electrode core and produce current. Current flow in the core can be measured by a current measuring device. The current flow can be correlated to the concentration of tritium in the gas surrounding the electrode to provide an indication of the amount of tritium present. The device can be used in a static system or a system in which the tritium containing gas flows. The apparatus provides real time readings of the tritium concentration in gas.