I could only find 5 cases where a space craft carrying an RTG suffered a mishap. of those only 2 resulted in the release of radiation. Both of those were in the

I could only find 5 cases where a space craft carrying an RTG suffered a mishap. of those only 2 resulted in the release of radiation. Both of those were in the 60s. from Wikipedia: To minimize the risk of the radioactive material being released, the fuel is stored in individual modular units with their own heat shielding. They are surrounded by a layer of iridium metal and encased in high-strength graphite blocks. These two materials are corrosion- and heat-resistant. Surrounding the graphite blocks is an aeroshell, designed to protect the entire assembly against the heat of reentering the Earth's atmosphere. The plutonium fuel is also stored in a ceramic form that is heat-resistant, minimising the risk of vaporization and aerosolization. The ceramic is also highly insoluble. it also notes that the LEM on Apollo 13 carried a RTG, and there was no sign of contamination after it re-entered and landed in the Tonga Trench. And that was a extreme outlier due to the high velocity it re-entered at being it was following a trans lunar trajectory.