A review of low-level tritium systems and sensitivity requirements.

Data from three international intercomparison projects are used to study the state of the tritium low-level technique and to set a realistic sensitivity level that should be demanded in ultralow-level tritium work, mainly in hydrology and oceanography. Only two laboratories reach the required goal, a standard deviation < or = 0.03 TU for weak samples. The methods used are described and important parameters illustrated graphically. Possible improvements in the measuring techniques are discussed, including the design of better counting systems.