Radioactivity detection device and detection method

The invention discloses a radioactivity detection device. The radioactivity detection device is used for detecting the radioactivity of a gas inside a spent fuel transport container, and the spent fuel transport container is provided with a first interface and a second interface which communicate with its inner cavity. The radioactivity detection device comprises a cooling device, a detection device and a gas circulating pump. After the detection device is connected with the gas circulating pump, two communicating interfaces are formed. Among the two communicating ports, one interface is connected with the first interface, and the other is connected with the second interface such that a detection loop for circulating flow of the gas in the spent fuel transport container is formed between the spent fuel transport container and the radioactivity detection device. The cooling device is arranged between the first interface and the detection device for cooling the gas in the detection loop. The invention further discloses a radioactivity detection method. By using the technical scheme provided by the invention, the operation is safe, the convenience is high, the accuracy of a measuring result is greatly improved, and the safety of the spent fuel transport container and a spent fuel assembly is guaranteed.