A low background automatic scintillation counter YSJ-SH79 was developed. In this instrument we adopted the technology of optical crosstalk discrimination and the four layer shield combined by lead

silver

copper and perspex. The samples are fed from underneath and samples can be automaticlly measured in turn. The quality reached by the instrument for

14

C is as follows: the background is 2.222 cpm the detection efficiency is 78% and the figure of merit is 2738.