A method for removing lead-210 (.sup.210Pb) from a metal, the method comprising determining a .sup.210Pb concentration in a metal to be refined; determining an amount of low alpha lead to be added to the metal to be refined from the .sup.210Pb concentration, the low alpha lead having a .sup.210Pb concentration below that of the metal to be refined; forming a doped metal mixture by adding the low alpha lead to the metal to be refined; refining the doped metal mixture to separate at least a portion of the lead in the doped metal mixture to form a refined metal having a .sup.210Pb concentration lower than that of the metal to be refined.

Ultrasonic probes containing a plurality of gas delivery channels are disclosed, as well as ultrasonic probes containing recessed areas near the tip of the probe. Ultrasonic devices containing these probes, and methods for molten metal degassing using these ultrasonic devices, also are disclosed.