W-K alloy has many advantages, such as high melting point, the resistance to thermal shock, and excellent resistance to helium hydrogen plasma irradiation. The key is the formation of potassium bubbles which can stabilize the grain boundary, act as pinning point and refine grain of W-K alloy, thus the properties of materials can been greatly improved. Positron annihilation lifetime spectroscopy (PLAS) is extremely sensitive to the concentration and size of nanoscale defects. In the paper, the values of positron lifetime in W-K alloy at different potassium contents ware measured by the method of positron annihilation lifetime spectroscopy. According to the two-state capture model, the positron lifetime spectrum was fitted as two-lifetime component, and the data were processed and used to analyze the change of concentration and size of potassium bubble in the W-K samples.
