alt Hacker NewsI found the specs for the fuel source: https://upload.wikimedia.org/wikipedia/en/e/e9/SNAP-19C_Moun...
The high-power unit had 300 grams of Pu-238 in 1965. Given its 87.7 years half-life, only 187g of Pu-238 remaining. It's very hard to do much damage with this amount of radioactive material.
It decays to uranium-234 though, which still isn't exactly nice. It'll be a long time before it's a block of inert lead.