I 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.

U-234 is ~3000x less radioactive than Pu-238, so having ~120g of U-234 is negligible.

I really fail to see a problem with these tiny amounts of non-brittle material embedded into a solid case. It's still very dangerous, but it's locally dangerous (meters away), not at the scale of whole countries.

Around three pounds, and something like 40% of it has already decayed away since this happened in the 60s.