-

Tritium(T1/2 =12.35 y) is constantly being produced in the upper atmosphere by nuclear reactions due to cosmic rays interaction with the atmospheric constituents. Tritum thus produced is immediately oxidized to H2O and mixed with the atmospheric HO . Natural tritium was first detected in water by von Grosse et al, in 1951, using electrolytic Concentration and gas counting.
With the advent of thermonuclear weapon test in 1954 tritium content of the upper atmosphere was increased by several orders of magnitude. This increasing will be continued as far as the weapon test is put in action. Even this situation, measarement of tritium in the environmental materials is still difficult, because of its low level and low beta energy.
In this paper the coneentration of tritium in several sea water sample are measured by liquid scintillation counter “LSC-LB1” made by Aloka Co. ,LTD. Figure of merit (FM) ,measuring time and procedure of sample prepration of this LSC Counter is compared to the best gas counter. Because of the large sample
Volume (100 ml) low background and easy prepration we think that this kind of LSC Counters, for low level tritium measurement, are preferable.