Abstract: The invention provides a method and device for applying radiation to a wound cavity resulting from a lumpectomy. The device comprises a non-deformable body of PTFE or similar material, with a rounded head and elongate stem or handle. The stem defines a channel which extends to the centre of the head for receiving a radiation source from a High Dose Rate, Remotely Controlled After-loading Brachytherapy Unit (HDRRCABU). The head of the device is inserted into the wound cavity and the wound is closed, so that the tissue forming the wound cavity is given a precisely controlled dose of radiation in a matter of minutes/hours rather than days/weeks.