It's a legitimate concern. Although the fuels in RTGs (PU 238) will not engage in a chain reaction, like a traditional nuclear reactor, they could be used to fa

It's a legitimate concern. Although the fuels in RTGs (PU 238) will not engage in a chain reaction, like a traditional nuclear reactor, they could be used to fashion dirty bombs. No such uses are known, but the material has caused serious radiation burns. https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#Theft https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...