A sample transfer system for nuclear irradiation and a method of automatically irradiating sample containers is disclosed. The sample transfer system includes a conduit which may define a passage for transferring a plurality of sample containers, an input assembly which may be configured to allow the plurality of sample containers to pass through the conduit in a predefined order, and an exposure assembly which may be configured to receive the sample containers via the conduit and rotate the sample containers in front of a radiation source.