γ sources offer a radionuclide with gamma emissions and X-ray emissions. For low energy gamma sources such as ²⁴¹Am, ²³⁸Pu and ⁵⁵Fe, with the energy below 60 Kev, gamma emissions can be stopped by high-atomic-number materials such as 5~10 mm thickness Pb. Particular attention should be given to the integrity of window, and care must be taken to prevent the ingestion of radioactive elements. For high energy gamma sources such as ⁶⁰Co and ¹⁹²Ir, gamma emissions can be stopped by high-atomic-number materials such as Pb and Fe. Attentions should be paid to the external irradiation, the protection means of which including reducing exposure time, increasing exposure distance and using effective shielding materials. ⁵⁷Co is sealed in the stainless steel capsule.