LI Wenjie, LU Xuejun, YANG Baoxing
(State Key Ceramics Testing Lab of Tangshan Entry-exit Inspection & Quarantine Bureau, Tangshan 063000, Hebei, China)

Abstract: This paper sketched the theory of radioactive samples’ decay balance cycle The specific activity of three groups of specimens with the radioactive decay balance time between 0 to 27 days was tested by sodium iodide γ-ray detector, then the differences between test results of the same specimen after different decay balance time were analyzed using t-test method. Researches show that if the significant difference between the test results is 5%, the shortest radioactive decay time should not be less than 12 days.

Key words: ceramic materials; radionuclide; measurement; the decay time of specimen; the shortest decay balance cycle