idea looks good, but one thing to point out: Most RTGs irl use plutonium, and are extremely easy to shield the radiation from, as they mainly emit alpha radiation, which is mostly harmless if it is outside your body (skin blocks it). the same is true for uranium and thorium, as the gamma produced from their decay is minimal. The main reason why coal plants result in such a high effective background radiation (still less than average background) is that the uranium and thorium are dispersed into the air, where they can be breathed in, which is where alpha radiation becomes the most dangerous (maybe second most, after certain specific energies of neutron radiation)
edit: another thing to note: RTGs produce significantly less energy/mass of fuel over their life time than an induced fission system. This is due to the significantly greater change in size of nuclei for the fission over the decay method. Fission systems are also much more energy efficient for the stage after heat production, as they produce enough heat to use conventional steam systems, which are on the order of 30-40% efficient for thermal -> electric, whereas RTGs struggle to get much higher than 10% for thermal -> electric. The primary advantages of RTGs are small size and lack of moving parts, which allow them to be used in places which the larger, conventional plants cannot be used.
Which is where they come in for people who cant be bothered for the more expensive but much more producing Steam powered reactor.