| abstract |
A nuclear heart pacer having a heat-to-electricity converter including a solid-state thermoelectric unit embedded in rubber which is compressed to impress hydrostatic precompression on the unit. The converter and the radioactive heat source are enclosed in a container which includes the electrical circuit components for producing and controlling the pulses; the converter and components being embedded in rubber. The portions of the rubber in the converter and in the container through which heat flows between the radioactive primary source and the hot junction and between the cold junction and the wall of the container are of thermally conducting silicone rubber. The primary radioactive source material Pu238 is encapsuled in a refractory casing of WC-222 which in turn is encapsuled in a corrosion-resistant casing of platinum rhodium, a diffusion barrier separating the WC-222 and Pt-Rh casings. The Pt-Rh casing is in a closed basket of tantalum. The tantalum protects Pt-Rh from reacting with other materials during cremation of the host, if any. The casings and basket suppress the transmission of hard X-rays generated by the alpha particles from the Pu238. The outside casing of the pacer is typically of titanium but its surface is covered by an electrically insulating coating, typically EPOXY resin, except over a relatively limited area for effective electrical grounding to the body of the host. It is contemplated that the pacer will be inserted in the host with the exposed titanium engaging a non-muscular region of the body. |