This heat is then converted to electricity by a thermoelectric converter which uses the Seebeck effect, a basic principle of thermoelectricity discovered in 1822. Each RTG contains 18 separate heat source modules, and each module encases four plutonium-238 pellets. An outer covering of graphite provides protection against the structural, thermal, and eroding environments of a potential reentry. Additional graphite components provide impact protection, while iridium cladding of the actual fuel cells provides post-impact containment. The fuel is in the form of plutonium-238 dioxide, a ceramic material which is resistant to fracturing.
Plutonium is dangerous only if very small particles become lodged in the lungs.
Depending on where it lands it would be recovered or left there. An outer covering of graphite provides protection against the structural, thermal, and eroding environments of a potential reentry. Additional graphite component provides impact protection, while iridium cladding of the actual fuel cells provides post-impact containment. The fuel is in the form of plutonium-238 dioxide, a ceramic material which is resistant to fracturing. RTG remains in one of the deepest parts of the Pacific Ocean.