I apologize for the false info I gave on this. Pacemakers are powered by ordinary batteries that last at least 10 years and replacing them (every 10 years) is a trivial operation. Even I, a dedicated backer of plutonium use, wouldn't recommend it for this purpose. Bernard L. Cohen Physics Dept. University of Pittsburgh Pittsburgh, PA 15260 Tel: (412)624-9245 Fax: (412)624-9163 e-mail: blc+@pitt.edu