~(135)Cs with a half life of T1/2=2.3×106 a is an interesting nuclide in studies of the dispersal of nuclear material in the environment.Preliminary measurements of ~(135)Cs with accelerator mass spectrometry(AMS)have been developed at China Institute of Atomic Energy(CIAE).In order ~ (135) Cs with a half life of T1 / 2 = 2.3 × 106 a is an interesting nuclide in studies of the dispersal of nuclear material in the environment. Preliminary measurements of ~ (135) Cs with accelerator mass spectrometry (AMS) have been developed at China Institute of Atomic Energy (CIAE) .In order