Removal of ²²²Rn daughters from metal surfaces

Removal of the long-lived ²²²Rn daughters (²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po) from copper, stainless steel and germanium surfaces was investigated. As cleaning techniques etching and electro-polishing was applied to samples in a form of discs exposed earlier to a strong radon source. Reduction of the ²¹⁰Pb activity was tested using a HPGe spectrometer, for ²¹⁰Bi a beta spectrometer and for ²¹⁰Po an alpha spectrometer was used. According to the conducted measurements electro-polishing was always more efficient compared to etching and in case of copper the activity reduction factors for ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po were between 200 and 400. Etching does not remove ²¹⁰Po from copper but works very efficiently from germanium. Results obtained for ²¹⁰Pb and ²¹⁰Bi for etched stainless steel were worse but still slightly better than those achieved for copper