The quality of calibration standards can deteriorate due to physical & chemical phenomena (eg. Degradation of liquid’s homogeneity, loss of active deposits’ adherence over time) and usage conditions (frictions, dust…).
From a physical integrity standpoint, the recommended working life of sealed sources according to ISO 2919 is 10 years in normal usage conditions (usage guidelines provided with our sources).
From a metrological standpoint, our metrological values are valid in our calibration’s conditions. We recommend using these values no longer than 2 radioactive periods, with a maximum of 2 years from the reference calibration date, due to cumulative uncertainties from radioactive periods as well as interactions between matter and ionizing radiations.